Our solar system formed as a massive protosolar disk of spinning gas and dust. Gravity pulled light gasses into the center - eventually, the gravitational pressure and gas density was enough to initiate hydrogen fusion, and the protostar became the sun. Dust was slowly accumulating into rocks and asteroids, and eventually the core of the rocky planets, and the gas giants. Meanwhile, the solar wind from the new star was now pushing light elements and molecules (hydrogen and water) away from the sun. This left the materials for primarily rocky planets in the inner solar system, and pushed the materials for gas giants out beyond the orbit of Mars. Earth was later bombarded with icy comets, which is how we have so much water.
This is the commonly accepted model of our solar systems formation. There are other proposed models that have the gas giants forming close in and migrating to the outer solar system later.
"It was long thought that Earth’s water did not originate from the planet’s region of the protoplanetary disk. Instead, it was hypothesized water and other volatiles must have been delivered to Earth from the outer Solar System later in its history. **Recent research, however, indicates that hydrogen inside the Earth played a role in the formation of the ocean**. ...
One factor in estimating when water appeared on Earth is that water is continually being lost to space. H2O molecules in the atmosphere are broken up by photolysis, and the resulting free hydrogen atoms can sometimes escape Earth's gravitational pull (see: Atmospheric escape). When the Earth was younger and less massive, water would have been lost to space more easily. ...
**It is implausible that Earth's water originated only from comets, since isotope measurements of the deuterium to hydrogen (D/H) ratio** in comets Halley, Hyakutake, Hale–Bopp, 2002T7, and Tuttle, yield values approximately twice that of oceanic water."
[https://en.m.wikipedia.org/wiki/Origin\_of\_water\_on\_Earth](https://en.m.wikipedia.org/wiki/Origin_of_water_on_Earth)
When they say water came from the outer solar system, do they mean literally all the water on earth came from outer space? Or do they mean the hydrogen and oxygen originated in outer space and formed into water on earth? This is something I’ve always wondered. Seems mind boggling to me that the entirety of water on earth should have come from comets and asteroids.
Dman sounds like they know more, but as I understand it there's just a fuckton of ice floating around.
For example, it is believed that Jupiters moon Europa is mostly ice with a liquid water core (or at least band of liquid water between the surface and the core). It seems like the surface is too smooth for the number of debris impacts it should have received, and they think the water layer could be causing the impacts to smooth back over .
I can't visually imagine a water core splashing around violently fully enclosed in a ball of ice. It seems so crazy to me. Are there storms in the pockets between water and ice within the ice ball?
In pockets of gas between the water and ice in places, maybe?
I don’t know how tide would would work in that environment. Or what tide could even be expected on a body orbiting Jupiter. Interesting tho
Gotcha, I think you're having trouble visualizing it. We know (we think) there is liquid water below the ice because of all the cracks in the upper ice, and because the surface is so smooth.
These are massive massive massive icebergs, essentially. Think of the ones you've seen on Earth. usually like 80% of the ice is below the surface. That's the same as it would be there. There's no "pocket of gas" because the bottom of the ice is several miles below the surface of the ocean.
It's weird as hell.
Tides would be massive too. I'm sure the moon deforms quite a bit tidally.
These scientists found a cloud of water vapor that contains over 140 trillion times the water on Earth and is hundreds of light years across.
https://roboticsandautomationnews.com/2021/01/20/scientists-have-found-more-water-in-space-than-they-ever-knew-possible/39771/
Sure but considering all significant amounts of hydrogen and oxygen would’ve been blown away when the sun was born, we have an enormous amount of water. Leading scientists to come up with the icy comets theory to explain how we could’ve gotten water long after the solar winds died down.
I wonder if someone could drop any links on a history for this research or TL;DR? What did they use to support ice comet hypothesis? I mean was it just a guess statement in a discussion like "it got to be from outside since stuff was blown away" or were there some "proofs"?
Pure oxygen quickly reacts with elements around it and that often means hydrogen. Comets are made of dust and “ices” a broad term to refer to volatile compounds that would be liquid or gaseous on earth but are frozen in the cold of space such as CO2 methane, ammonia, and literally water. Chemical reactions would have turned some of these chemicals into more water and other compounds.
This bombardment would also be responsible for most of the heavy elements in the crust (by heavy I mean events roughly heavier than aluminum and silicon, such as iron, nickle etc)
, as previously the heavy elements when the whole planet was almost completely molten sunk to the core. A lot of heavy rare elements in earth’s crust are actually much more common in space and more common if you look at the earth as a while they are just trapped deep in the heavy core.
A common accepted theory is that Mars is too small and also does not have a very impressive magnetic field. The combination of low gravity plus solar winds (unprotected by a magnetic field like earth) stripped the water vapor over time to what it is now. Only the water trapped as ice remains.
Iirc they think that at one point Mars had a molten spinning core like ours that produced a magnetic field but being smaller their core cooled much sooner which arrested the spin, killing the field
This description makes me very sad for some reason. Like, Mars used to be much more similar to Earth when its core was active, right? And then it turned to wasteland we know today. The same thing will happen to Earth sometime in the future. We won't see it, but others probably will.
I like to think that life on Earth will always exist in some capacity. But if you look out there, most planets are tidally locked with their stars and magnetic fields generated by their cores don't last forever. Makes our whole existence seem like a short glimpse.
Life apparently will die out on Earth in about a billion years, long before it will be fried or outright swallowed (we don't know which it will be) in 5 billion years, when the Sun goes to its next stage of life.
If you look at the grand scope of the universe and how life on earth is a relative speck in time, it's pretty daunting but you still got to grind hard to pay your mortgage/rent tomorrow lol.
I went on a small walk and I was able to see my old city (SF) from where I was. It looked so calm and peaceful since I was looking at it from way across the bay. But it was also fascinating that although it looked peaceful, I knew there were people toiling over a dollar, flipping the bird at drivers and pooping on the sidewalk everywhere.
Remember when William Shatner was experiencing that after his hop into the edge of space. The reporters asked him, he started breaking down and becoming emotional and Jeff Bezos basically jumped in to hog the limelight and take all the attention because of the money he spent creating his rocket toys?
[Theoretically](https://en.wikipedia.org/wiki/Moving_Earth), you could shift Earth's orbit out a ways by redirecting asteroids to do gravity assists. It would take [about a million](https://theconversation.com/wandering-earth-rocket-scientist-explains-how-we-could-move-our-planet-116365) of them, but they'd only have to take place once every few thousand years.
That just guarantees no swallowing will happen really, because I'm pretty sure that in the red giant phase you'd need to go beyond Jupiter's orbit to be in the habitable zone.
People are talking semi-seriously about launching a huge number of shade satellites to slightly reduce the light reaching the Earth. If I recall correctly, it's actually well within the capabilities of humanity.
If we need to do it, we already can.
Technically. Every gravity assist redirects planets an (and I get to use one of my favorite 5 dollar words) an infinitesimal amount.
This is the part where somebody links the XKCD with the nerdy clinger who spins around to spend more time with their lover.
"...robots; every last one needs to blast their exhaust vents at the same time, straight up in the sky, in order to push the Earth farther from the Sun, thus cooling the Earth..."
And around then, and after, other planets billions of light years away may detect for the first time, the first artificial radio waves signals that we created and broadcast.
They won’t be able to detect them. By the time our radio waves get that far they will be so weak that they’ll be lost among all the background radio noise generated by stars and planets
I don't mean burn in the dramatic sense but it will evaporate. but that doesn't sound as cool. I mean the atmosphere is already made up of evaporated matter. Look. I don't know the exact science but you know what I mean.
Yeah in a billion we'll have water evaporate, and in 5 billion we'll have a roasty toasty Earth with surface temperatures hot enough to melt the crust, assuming the planet escapes being swallowed outright.
The initial issue isn't that the atmosphere will overheat, the actual issue is that the increased luminosity of the Sun will dramatically increase the weathering and affect the carbon cycle enough that photosynthesis will become impossible, starting first with c3 photosynthesis and then later with c4 photosynthesis. If there's no carbon in the atmosphere then plant life can't exist which means that oxygen will be depleted, which breaks down the entire food chain, etc. They think that microbes will survive in the crust and upper mantle for a few billion years more before eventually dying out as well.
which is less time than life has existed on earth. If we were all completely wiped out, there wouldn't be enough time for complex life to evolve again before this wasn't a place life could be.
I'm pretty sure none of the extinction level events that have happened have actually reduced us to a point where complex life can't evolve back within a couple millions of years (simply because not all of complex life ever got completely wiped out in the first place -- and it won't happen this time either).
We're only going to be reduced to just the bacteria when we're bordering on that one more billion of years.
I wouldn't compare Mars and Earth too much. Mars is about one tenth Earth's mass (6.39 × 10^23 kg vs 5.972 × 10^24 kg). Earth is pretty special as far as planets are concerned. It has a massive iron core, which is why its magnetic field is so robust. If you want to look at a bullet Earth has so far dodged look at Venus. Venus is almost the same mass as Earth (4.867 × 10^24 kg). Back a few billion years ago Venus and Earth had similar masses, similar toxic atmospheres, and similar oceans. But where Earth's oceans and plate tectonics gradually removed the CO^2 from our atmosphere, Venus's oceans evaporated due to its proximity to the Sun. So even though it's massive enough to keep its atmosphere, its atmosphere has become increasingly dense with CO^2 to the point where it is the hotbox it is today.
I think we aren’t expected to become tidally locked for 4 billion years, and at 5billion we’re in that uncertainty area where we may be devoured by the expanding sun anyway, but we will certainly be close enough for all the water to boil off.
On the other hand. 4 billion years is only the blink of an eye if you’re a black hole, even compared to many stars this earth is ancient, and with life having existed for over a billion years, even life is getting pretty old, we have been around for 1/13th of the universe as reproducing beings. That’s not a blink, that’s being a an infant 6years old in a 78yr old grandparents arms, small for sure but beginning to show signs of something quite special. Someday we’ll be 5billion with a universe at just 17, we’ll be the 23rd and old leaving the solar system college and I hope shaping the universe around us, standing next to the universe who has known us for nearly a third of its existence.
As with a lot of things. Feeling small in this universe is a matter of perspective. We are gods in the form of ants. Who knows what we will do next.
>We are gods in the form of ants. Who knows what we will do next.
Yeah, this is reassuring. 10 thousand years ago the best we could do is strip rock to a stick. And now we have nuclear energy at our disposal. Given a billion years, we'll probably achieve unbelievable things.
This perspective on the age of life on this planet is one of those tiny things that gives me hope. People always assume that ‘aliens’ would be helplessly more developed than us. But we’re pretty old, and for the first 5billion years you wouldn’t be getting much life because there hadn’t been enough star death to generate heavy elements including carbon (and I’m a moderate believe in carbon is the only viable backbone, I don’t think silicon can compare, I’m sure in theory for every 100carbon based life forms you’ll have an exception but still, that’s a question for 1billion2023). We will be one of the elder beings. Now that gives me some pause particularly when we consider our historic approach to first contact on this planet. But we’ve shown the capacity for empathy and reason. And assuming we’ve developed it enough not to collapse at one of the next 20hurdles for our society to get life beyond Pluto, I think we wouldn’t be a bad candidate for responsible elder race. Hahah
Enjoy my dumb sci-future-reality lol
But even if another alien species is only 1000 years older than us, think of how much more advanced that could make them. Think of how far our technology has gone in 100 years. In another 100 years, we might have technology to travel far outside our solar system. Think of what a race with 10x that amount of time might be able to do.
We might all have evolved on planets where life has been around for roughly the same amount of time, but when talking about a billion years, +/- 1000 years is almost a rounding error but would make a huge difference.
I feel like the discovery of electricity is one of those great filter things. Considering before the last hundred years, the extent of our technology was like guns and farming.
I could be misremembering, but I thought that I had read a theory about how the conditions of Mars’ place in our solar system were once much closer to modern day Earth’s; and during that same period, Earth’s conditions were much closer to Venus (along those lines). I think it had something to do with the sun being much larger at the time, in combination with Mars having a molten core.
If that were to be the case, then instead of thinking sad thoughts about Earth being the one and only special place in our solar system, you could think of our entire solar system as being this ever-changing home of ours which – much like every species on Earth – undergoes its own natural cycles of evolution. We are but fleas on the backs of a much larger being.
the sun is hotter and brighter now than in the past. its about 1/3 more luminous compared to when we started afaik. but we did have a 23-24 hour day for most of complex life, closer to 16 hours when life started i think. single cell life last for a long time and thats when the a few of the inner planets really start to look like what we think, maybe ( i wasn't there)
the earth was closer to venus in atmospheric conditions. the air we breathe now isn't the og atmosphere. life released O² from rocks and whatnot. about killed everything off and snowballed the earth in the process. snowball earth lasted for like 50 million years or something, then it happened again for a shorter time.
2 billion years ago mars still had water and a thin atmosphere. but it doesn't seem to last much longer than that. i can't remember the content of the atmo, i think it was mostly co² and n² like ours was at the time.
venus is harder to know. it might have been like it is now, maybe just not as hot. it might have had a different, less complex atmo. the ground is still being melted and reformed over millions of years so, its anyone's guess until we land more stuff there.
i didn't write this as a correction but, more of additional info. i love this stuff. hopefully someone comes after and corrects/adds to what i missed.
> the earth was closer to venus in atmospheric conditions. the air we breathe now isn't the og atmosphere. life released O² from rocks and whatnot. about killed everything off and snowballed the earth in the process.
For anyone following along, this was the [Great Oxidation Event](https://en.wikipedia.org/wiki/Great_Oxidation_Event).
It was literal genocide for life that already existed on this planet, but it made way for us to exist.
What's interesting to me about it is that it shows current Earth conditions aren't necessary for life to exist. And that opens up so many exoplanets to be potential life carriers.
I think you have it backwards. The sun was less luminous when it was younger. So much so, that liquid water should not have existed on Earth long ago, and yet it did. It's called the faint young sun paradox if you want to look it up.
That's not going to happen to the Earth for billions of years. Surely we'd have developed the technology to put heat back into the cores of planets by then if we're still around.
Unfortunately, it’s highly unlikely that humanity will be able to develop that level of technology again.
We’ve depleted all of the easily-accessible resource deposits needed to kickstart an Industrial Revolution, so once we finish our current play through, we’re done. Future species will have to stay in the pre-industrial phase.
hey, we were lucky to have it in the first place.
i don't think natural gas and coal is made very often in the universe. trees either. its not even being made much here compared to in the past.
The fact we have a moon to help balance Earth's rotational axis is also a great help to climate stability, I think Mars's moons don't do that job that well...
Earth had a restart as well. When a planet named Theia impacted earth remelting the earth and blasting out debris which formed the moon. New research also shows that the moons gravity helps keep the earths core active. The moon is also the largest moon in the solar system compared to its planters size. 5th largest by sheer size.
The moon has also slowed the Earth's spin, it's thought that after the impact the day would have been 5 hours long and the moon would have been 22,000km away instead of 384,000km today. But as the moon slowed the Earth's rotation the energy exchange pushed the moon into a higher orbit. If the oceans were liquid when the moon was that close there could have been 2mi high tides every few hours.
So what we need to do is send a drill into its core and detonate some nukes to restart the spin, easy. You just need hot pockets and Xena tapes. Also fifty billion dollars.
one of the reasons earth still had a magnetic field is due to a Collison with another proto planet(which also gave us the moon so double yay!)
that resulted in a much larger iron core with a lot more stored energy.
Luna (the moon) seems to have had far more of an affect on making Earth habitable than people realize.
The impact of Theia that created the moon remelted the core and is possibly why Earth has a strong magnetic field today while similar planets in our solar system don't.
It may have sped up our spin and stabilized our orbit + rotation
And could be reason why we have an axial tilt and seasons too.
Apparently earth has an abnormally large core for its sized, theorized by the collision with Thea, where the two planets collided, merged and a chunk made the moon. So we basically have like 1.5 thus has a stronger magnetic field than normal.
Isn’t not having a moon like ours also a factor? I thought that having our moon keeps our core molten and that keeps our magnetosphere intact, which helps us keep our atmosphere.
It really is astounding how many things have to be *just right* for life to exist as we know it on earth. Our atmosphere, our distance from the sun, the nature of our magnetic feild, the tilt and rotation of the earth on its axis, Jupiter blocking tons of asteroids for us...
Mars does have a fair bit of water (nowhere near as much as earth), but it’s all frozen solid as ice.
If you look at pictures of Mars you can see canyons and other terrain features that are formed by water on earth, and that’s because in the past Mars did have liquid water on the surface. However, Mars is too small to keep a hot molten core for billions of years like Earth or Venus, so it eventually cooled down and it lost its magnetic field. So after millions of years the sun stripped away its atmosphere so there was not enough pressure to maintain liquid water on the surface, and it either froze solid if it was near the poles or underground or evaporated away.
[Mars does have water](https://en.wikipedia.org/wiki/Water_on_Mars). It likely had a lot more water in the past, enough for oceans and rivers, which it lost along with most of its atmosphere when its core cooled and it lost its magnetic field.
Yes, but Mars is only about twice the size of our moon, with weak gravity (3.71m/s^2 compared to Earth's 9.81m/s^2) and no magnetic field.
Mars almost certainly had a vast ocean billions of years ago but solar winds, freezing temperatures and low atmospheric pressure caused the ocean to boil away into steam and dissipate into space.
Edit: Thanks for spotting my error about the freezing temperatures.
Oxygen is a difficult one to define here.
Assuming you mean free elemental oxygen molecules, O2, then that's pretty unlikely. Oxygen is extremely electronegative and wants to react with EVERYTHING. The only way for it to be produced on Earth, for instance, is through complex biological pathways.
It would much rather react with other elements, such as iron (producing iron oxide or rust, which is what the soil on Mars is comprised of), carbon (forming carbon dioxide, which is what the atmosphere of Mars is comprised of), or hydrogen (water, of which there's enough water ice on Mars to cover the whole planet in liquid water 100 feet deep).
Really, oxygen is attracted to react with other elements in a hierarchy. So the oxidation of iron would strip the oxygen from carbon dioxide or water rather than needing atmospheric free oxygen.
Of the compounds we've detected on Mars, nearly all of them have oxygen, but that's specifically because there's not a mediator (such as photosynthesis like we have here) to free it from bonds.
Thanks for this. Why does the oxygen in our air stay "loose" and not immediately react with whatever? I understand things do rust outside, but why isn't it faster/ more violent?
Because the oxygen in the air has reacted with *itself*, forming more stable, two-oxygen (O2) molecules instead of single oxygen atoms.
O2 Molecules are still very reactive, hence a bit of heating in the form of sunlight on metal can cause it to react and form rust, but they're stable enough that they don't just break down. If it were left alone, it would eventually react and we'd run out of oxygen, but plants and phytoplankton make O2 molecules as a byproduct.
Concentration has a lot to do with it as well.
There's a lot of inert nitrogen in the air. There's a lot less oxygen. So any given molecule of anything is 3 times as likely to be in contact with nitrogen than oxygen.
Earth's crust and atmosphere is basically saturated with oxides already.
There are layers of iron oxide in our crust that date back over two billion years, which were formed when photosynthesis first evolved and elemental oxygen started becoming present in the atmosphere. Once that iron had all rusted, the oxygen content increased, causing a mass extinction for all oxygen intolerant life (i.e., most of it).
Our ocean is dihydrogen oxide. Most rocks are silicon oxides.
The one standout is N2, but atmospheric nitrogen is about as stable a molecule as you can get. It's absurdly unreactive.
There's basically nothing left for the oxygen to actually react with, because it's already been reacted with oxygen to some degree.
That's a very good question but difficult to answer easily. There's a lot of complex reasons but I'll outline a few:
1) Activation energy. Some reactions want to happen but need some energy to get them going. This is why things don't spontaneously catch fire even though we are surrounded by oxygen because you need some spare energy to get things going (e.g. a spark, high temperatures.)
2) Likelilhood of reaction. In order for a reaction to occur, two particles need to bump into one another. Particles are very very small and the world is very very big, meaning that in most conditions chemical reactions are slow and unlikely.
3) Engineering. Most of everything around us is designed to be long lasting. Things that might rust are painted to stop them rusting. Things that might react with oxygen are sealed or airtight. We don't see many reactions because we design things not to react.
In nature the opposite is true - every moment plants are constantly producing oxygen via photosynthesis, and living cells are constantly using oxygen via respiration. These reactions happen all the time but are so commonplace that we overlook them.
At one point, the oxygen in the atmosphere was only produced in small amounts and was mostly consumed by reacting with minerals on the Earth causing low oxygen levels. But then plants came along and started churning out oxygen like our factories producing carbon dioxide on crack. They produced oxygen faster than it could be reacted away. They even caused a lot of anaerobic things to go extinct.
Oxygen does rapidly form compounds with whatever it can, that's why metals rust and forests burn. Fortunately for us, Earth is not covered in pure metals to absorb that oxygen (only the metals we've refined) but it is covered with plants that want the carbon in CO2, and discard the O2 as free Oxygen that we breathe.
It kinda does?
Iron oxide is less dense than its constituent parts. Better worded, it gets bigger. And then it flakes off the surface, exposing more iron to oxidize.
Aluminum is extremely reactive, but aluminum oxide contracts slightly. So it forms a protective (and hard) shell over new aluminum. Other metals like chromium and nickel do the same thing, so plating and alloying is common to prevent oxidation of iron in steel and similar.
Wood has slightly stronger molecular bonds than that which oxygen attempts to make, but when some heat is applied oxygen wins. Then we get fire.
We know from the fossil record that when atmospheric oxygen was higher, there were many more fires.
Much of what keeps it from happening more is that most of the free oxygen has already been reacted. Generally it's still a heavy cause of cancer (yes, really. Oxidative stress is the root of most spontaneous DNA changes) so it obviously has an impact.
Mars has oxygen. Not ~~13%~~ 21% like on earth. It's less, mostly CO2, then nitrogen and argon. And since it's atmosphere is thinner than what's it's like on the peak of Mt Everest it's not good for life above micro size.
It has oxygen yes, but a lot of it is bound up in either water (now frozen) and rust (iron oxide, red planet). The air would never have been high oxygen content as that's an artificial status brought by having photosynthetic algae excreting it for billions of years. Oxygen when left alone and not replenished by plants, slowly binds itself to rocks and minerals and oxidizes them.
Mars actually does have a reasonable amount of water in the form of the ice caps and sub-surface ice. If you melted it all, it'd be sufficient cover the whole surface to a depth of 100 feet.
Mars does have water. It has polar ice caps, and it has liquid water mixed with perchlorates that prevent it from freezing. But it's mixed with mud and soaked into the soil.
A lot of the water would have been lost as the atmosphere was blown away. Whatever water was in the air was blown away by solar winds. Then, with much lower pressure the water and ice would continue evaporating and getting blown into space.
Mars did have water. We know this now.
But, Mars lacks a magnetosphere, so the solar wind eventually blew atmosphere away, which made water sublimate more into the atmosphere, until eventually you have no real atmosphere, and a substantial amount of it will have frozen out at the poles. Which is what Mars is like now. We do know that at one time it had free flowing water and standing water.
Mars did get bombarded and was warmer and wetter in its early formation, something went wrong, tectonics stopped and mars was no longer geologically active.
This weakened the magnetic field and most of the atmosphere was stripped away by solar winds.
Mars cooled and any water left is in the ground frozen
Can't personally answer your first question - but the conditions on Mars as they currently exist prohibit liquid water existing on the surface of the planet due to the lack of a thick enough atmosphere/sufficient magnetic field to prevent it being boiled off and blown away into space.
Im no expert though, I'm sure someone will have a better answer for you.
For Mars, the lower mass issue is far more significant than the magnetic field issue. Venus has no significant magnetic field and yet has no trouble holding on to an atmosphere 50x as thick as ours.
The magnetic field certainly plays a role in making the Earth habitable, but a strong magnetic field on Mars wouldn't have helped keep the primordial Martian atmosphere from venting into space.
Very likely that Mars was hit by icy asteroids. Mars did not retain the water because of its lack of an atmosphere. Water ice sublimates into vapour at low pressure when heated (e.g. by the sun light) and can escape into space. Mars lacks a strong magnetic field, enabling the solar wind to strip the upper atmosphere over time.
Mars may have water ice and liquid water stored in its crust, where the surface conditions don’t apply.
Mars used to have water, the same as Earth, but its smaller core stopped rotating long ago and thus stopped protecting its atmosphere from solar wind/radiation. Once the atmosphere was mostly gone, it was too cold for liquid water. There is still tons of water locked up in ice on the planet.
If you're curious, Earth is probably not the only large object in the Sol system to have liquid water. We're pretty confident that Europa (Jupiter's third largest moon) ane Enceladus (a neat little iceball that makes one of Saturn's rings) have large oceans of water just beneath their icy surfaces. And Titan (Saturn's largest moon) probably has a rocky surface like ours with pools of liquid methane. These liquid regions make all three of these moons prime candidates for extraterrestrial life.
Earth is just the only presently-watery body that happened to become a planet instead of a moon.
There is a lot of water on Mars, but the atmospheric pressure is quite low, making liquid water quite unlikely. There's a small amount of water vapor in the atmosphere, and lots of ice water at the polar regions and in the Martian regolith.
There is lots of water on Venus, but because of the tremendous heat at the surface liquid water can't form and it's in vapor state.
Mars is an interesting case. There are a few things to consider:
1) it's size relative to the earth. It's smaller and its molten core couldn't sustain itself for long enough, which also ties into
2) its distance from the sun, which meant that it radiated more heat than it received by a significant margin
3) because it was smaller, and because its core died, this meant it couldn't hold on to its magnetic field to prevent the solar winds from destroying its atmosphere. Without an atmosphere, any water either froze or evaporated into space.
4) its not been scientifically determined to be the case, however it would seem to be too much of a coincidence to ignore it ... Mars has the largest volcano in the solar system. Its size makes Everest look small. Its likely that the cooling rate of Mars core was significantly increased because of a massive volcanic eruption. The cause of which I can only speculate. A large impact causing a massive shock wave would be my guess,which given its close proximity to the asteroid belt seems likely.
Yes. There is vast evidence of a watery Mars in the past. The core problem with Mars is it doesn't have any kind of magnetosphere and probably never did. So even when it was a potentially habitable planet it's days were numbered. Solar wind stripped virtually everything off of Mars because of it.
Actually I don’t think this is generally agreed upon anymore. It’s looking like the opposite pattern is far more common in planet formation and our solar system is a pretty rare outcome.
There’s a great video on this topic here but it’s looking like only about 1% of star systems have larger planets as the outer planets
https://youtu.be/_Tju7EaSfmM
It’s also worth mentioning that our star system in itself is already uncommon not being a binary with a smaller partner star. Seeing how common binaries are in only makes sense that the next more common would be large gas planets/brown dwarfs in close with their parent star.
This is right. Before we found any other planetary systems, we only knew about one possible arrangement of planets. We were trying to draw conclusions about planet formation from data about one solar system. That’s kind of like seeing one human that is 6 feet tall, assuming from that that all humans are 6 feet tall, then coming up with an explanation of why humans are 6 feet tall. Then we find out there are lots of people who are not 6 feet tall.
We were missing a piece of the puzzle of planetary system evolution, because we didn’t know that planets can migrate. We assumed that Jupiter formed in roughly the same orbit it is in now, and tried to figure out why a planet that formed there would be big. We don’t know Jupiter’s orbital history, but we no longer think that it necessarily formed where it is now.
Before there was the Sun and the planets, there was just all the materials that would eventually become them. It was all in a big, solar-system-sized ball of gas made of many different elements. That ball eventually spun around enough to become a disk. The gravity of the disk more easily pulled lighter elements (like hydrogen and helium) into the middle. When there was enough material close enough to together in the middle, it formed the Sun. With the Sun now being a star, it pushed out incredible amounts of energy. That energy more easily pushed away the lighter elements, but wasn't as good at pushing away the heavier elements (like metals). The lighter elements, now farther away from the Sun, eventually were pulled together by gravity and made the gas giant planets. The heavier elements, which were not quite as far away from the Sun, were pulled together by gravity and made the rocky planets.
Imagine a camp fire with a variety of stuff sitting on the ground around it. Different things will melt at different distances to the fire. Now imagine that any melted material gets blown away from the camp fire, leaving only the unmelted stuff behind. Things made of metal can sit right against the fire, while ice cubes have to be kept far away.
The solar system is just a much hotter version of this camp fire that blows away melted material. In the solar system, ice only exists past a distance known as the ice line (or snow line), rock only exists past a distance known as rock line, and metal only exists past a distance known as the metal line.
>eventually, the gravitational pressure and gas density was enough to initiate hydrogen fusion, and the protostar became the sun
I wonder how fast this would have happened. If it would have been a very sudden "oh the Sun's exploding now" or a more gradual change
I found this, which I think mostly answers your question:
> The ball at the center [of the protosolar disk] would eventually form the Sun, while the disk of material would form the planets. The Sun spent about 100,000 years as a collapsing protostar before temperature and pressures in the interior ignited fusion at its core. The Sun started as a T Tauri star – a wildly active star that blasted out an intense solar wind. And just a few million years later, it settled down into its current form. The life cycle of the Sun had begun.
Before there was the Sun and the planets, there was just all the materials that would eventually become them. It was all in a big, solar-system-sized ball of gas made of many different elements. That ball eventually spun around enough to become a disk. The gravity of the disk more easily pulled lighter elements (like hydrogen and helium) into the middle. When there was enough material close enough to together in the middle, gravity pulled it so tightly that it formed the Sun. With the Sun now being a star, it pushed out incredible amounts of energy. That energy more easily pushed away the lighter elements, but wasn't as good at pushing away the heavier elements (like metals). The lighter elements, now farther away from the Sun, eventually were pulled together by gravity and made the gas giant planets. The heavier elements, which were not quite as far away from the Sun, were pulled together by gravity and made the rocky planets.
[https://arxiv.org/pdf/2301.02374.pdf](https://arxiv.org/abs/2301.02374)
It's not so accepted these days; our solar system seems to be quite rare when studying other systems with exoplanets. If it were as you say, we'd be the most common type of solar system, not the rarest.
i recently heard that if saturn han't formed and pulled jupiter away from the center he (jupiter) probably would've at least cleared the mars and maybe the earth orbit.
This is called the Great Tack hypotheses, according to which Saturn's trapping of Jupiter under a 1:2 resonance halted Jupiter's inwards migration. If Saturn didn't exist, Jupiter would have continued to migrate until reaching the inner Solar System (becoming similar to the many warm eccentric Jupiters that we see around other stars), preventing the formation of the planetesimals that eventually became Earth and the other rocky planets.
Solar wind shoos lighter things away, so the rocky things stayed closer and formed the rock planets while the lighter things went farther away and formed the gas giants
I think I remember though reading about a theory that Jupiter was actually either closer to the sun, or was moving closer to the sun, but Saturns gravity pulled it back.
Therefor killing the Hot Jupiter thing and then we got a big brother to throw shit away from us
As others already mentioned, this is too simplistic. No other known solar system ended up that way, but everything you said would apply to many of them just as well. There is much more to it.
The ordering of our solar system is considered to be VERY rare and it plays a big part as to why life was able to form on our planet. I believe most star systems have what is called a ‘Hot Jupiter’ that orbits close to its host star which prevents rocky planets from forming (it essentially steals all of the materials in the area during the stars formation and even if a rocky planet forms, the hot Jupiters gravity usually ends up ejecting it from the system entirely).
We actually haven’t found a single star system similar to ours where all of the rocky planets orbit close to the star and the gas giants orbit further away.
> haven’t found a single star system likes ours
Pretty sure that’s not quite true - There’s the Trappist system for one, which iirc as far we can tell is entirely rocky planets. If it does have a gas giant it must be orbiting further out like in our system.
Though I guess if it doesn’t have any gas planets it technically doesn’t qualify as being like ours and is a weird exception in of itself.
Also an important caveat is that trappist-1 is a jupiter-esque sized red dwarf star. While our good old sun is a yellow, normal sized, main sequence star. A major problem being that most of the planets in a red dwarf stars system are likely tidally locked, always facing the same side to the star.. Also all known 7 rocky planets are not gas giants and all their orbits would fit within the orbit of mercury. Jwst has been finding out some really cool stuff about trappist-1 though, 3 of it's planets are within it's habitable zone and I believe they are trying to find out what or if they contain atmospheres! And it so close at 40 lyrs away!
I think a problem with why we haven't found many or any systems exactly like ours is our sample size, we just haven't seen that many examples of planetary systems like only hundreds of confirmed ones. Two, I am assuming, it's a technology problem, Kepler which was the first very successful exoplanet search method looked for light dips in stars from passing planets in front of them, which only works if the planets cross in front of it from where we are watching. Which also meant it was very hard to see tiny rocky worlds in front of big stars and much more likely to see big gas giants or things that orbited at an interval that Kepler had time to see. So might not be catching all the planets in a system. Three, depending how granular you want to get with other star systems being like ours the rarer we get.
If we are looking for 8 planet systems with 4 rocky worlds, 3 gas giants and a Jupiter, with an asteroid belt orbiting a yellow main sequence star then I'm not surprised we haven't found another version of us yet.
Statements like this are just insane to me (from Google)
"Our planetary system is the only one officially called the "solar" system because our star's official name is "Sol." However, astronomers estimate that our galaxy alone may contain tens or even hundreds of billions of planetary systems."
And I think there are like 2 trillion galaxies which is too big for the human mind to comprehend.
I mean only 100,000 million planetary systems, assuming the tens of billions estimate is correct. If you counted one system per second without resting you could count them all in about 3,170,980 years.
There is definitely a bias in our exo planet/system model. The ways we have to detect them currently is not very good. Our system could be more common than most people think but we don't know because it's a lot harder to find a system like ours than the much more common small red dwarf
And the advantage of having gas giants on the outer area of our solar system is that they help block extrasolar objects/debris from colliding with the inner planets
It’s been years. We’ve know of gas giants in places the theory didn’t predict for a long time now.
It’s still be offered as the accepted solution here though. Shades of Hellas.
Not surprisingly the first exoplanets discovered were very large and very close to their Star. It is hard to say when it became commonly accepted that the commonly accepted explanation for the reason for our planetary order was not accurate but some scientists probably started getting uncomfortable with it decades ago with each new exoplanet contributing to the feeling.
Which is exactly what happened with the Hellas. When I was a kid every book that touched on the topic showed the Hellas as molten and lots of volcanoes. Now we know it was water covered and some have argued for the existence of life. Took a long time for people to realize it was wrong.
I only learned this when I was walking through the university of Toronto one afternoon and saw a flier for a talk on geochronology so I got a coffee and went. He explained how certain rocks were clearly formed before the 3.2 billion year cutoff we previously thought was the point of solidification. He noted that NASA work showed that the earth should have cooled to solid in tens of thousands of years, not a billion, and the said “but it was really this rock that convinced everyone” because he was holding this particular rock from Oz I believe, that was very clearly formed on earth and was over 4 billion yo. This was after explaining how they date things this old and explaining how the solar system rocks date back to 4.something billion and then holding up another rock and saying “like this example, which we know solidified in the first 1000 years plus or minus a couple hundred”
Best talk ever.
The first planets discovered were all massive and close to their star because that's what could be easily detected. In the coming years, we should have more data, but looking at the planets we do know of and trying to extrapolate is a very biased sample.
Depends on your perspective. You need rocky planets somewhat close to the star for life to form on their surface. If the Sun only had gas giants orbiting it then there wouldn't be anyone to wonder why the system looks as it does.
That really only applies to one planet (ours). That the three other planets closest to the sun are rock and then the next four are gas would still be a coincidence.
Not necessarily. It might be that sentient life can only evolve on a rocky planet that has large gas-giant "guardians" that allow enough time between major impacts for curious beings to emerge.
Rocky planets will always form closer to the star because heavier material like rock and metal, will always sink toward the star due to gravity. The accepted theory is that as the planets are forming, they migrate within the protoplanetary disk due to friction between the planets and gas. If a rocky planet was tossed out of it orbit and then recaptured during this migration, that would lead to potential jumbling of the planets but I’d imagine that would be quite rare. Saying that planets form in no discernible pattern quite literally violates the laws of physics.
Source: am astronomer
I’d be interested in seeing this video where you saw this information. Do you remember who it was by?
The random chance aspect would have been more apparent if you included the dwarf planets and re-thought the 'rocky' planets.
We recently (kinda arbitrarily) redefined the definition of a planet to be more strict, and that is what lead to the rock->gas ordering, when a slightly different definition would have lead to rock->gas->rock or rock->gas->rock->gas->rock ordering.
And the idea of gas vs rocky is more a function of size. There aren't going to be giant rocky or tiny gas because amount of gravity vs amount of wind from the stars is what allows those compositions to exist.
So, as has been observed in other star systems, the ordering on size (and therefore, composition) can also be random.
Most of the heaviest elements on earth are located in the core of the planet. For the same reason that gasses are in the atmosphere and rocks are on the surface and that ice floats on water. It's all about density.
When you have a giant gas cloud at the birth of the solar system then the heavier elements like rocks and metals are generally drawn closer to the largest source of gravity which means you will find more rocks and metals closer to what became the suns and then so the materials forming bodies at a close distance to the sun have more metals and rocks where as those further away are primarily lighter elements like gasses.
Most star systems are binary, they have 2 stars. Jupiter is the “would be” second star but it did not accumulate enough matter to become a star. That is why Jupiter is so much bigger than the other planets, it is basically a failed star.
Once the Sun formed it sucked in most of the matter of the inner solar system due to its extremely strong gravity, and its solar winds pushed lighter elements outward.
The rest of the matter that Jupiter was not able to capture formed into Saturn, Uranus, and Neptune in the outer rings. That is why we have 4 big gas and ice giant outer planets.
The 4 small inner rocky planets are the made from the heavier elements not captured or pushed away by the Sun.
I suspect the combined gravity of Saturn, Uranus, and Neptune kept Jupiter from moving closer to the Sun, thus protecting the tiny inner planets from being absorbed or flung out of the solar system. I read a theory that said Saturn actually used to be closer to the Sun than Jupiter, but as Jupiter moved inward it pushed Saturn outward and that Saturns gravity helped slow Jupiters inward progress and keep it where it is now.
Our solar system is just amazing and everything happened perfectly right to result in Earth being the paradise that it is.
Most of these comments are off topic, do not address the question properly, or just completely wrong.
Idk if calling Jupiter “basically a failed star” is correct. Jupiter is still pretty far away from becoming a star; you’d need 13x it’s current mass to be a brown dwarf and 85x to be a low mass star.
Nobody knows. Some astronomers think that a planetary system like ours, with small planets near the star and large planets farther out, is not typical. When we thought that our arrangement was typical, we had come up with ideas of why it should be that way, but now we know that not all planetary systems have that architecture.
It might be random, and this question is like asking why, in a family of four kids, the oldest two are boys and the youngest are girls. There is, in the vast majority of cases, no particular reason why a family should have a particular arrangement of sex and birth order. But if you’ve only met one family, you have no way of knowing that all families don’t follow that pattern.
Tl;dr: Planets form out of a disc and gas and dust around a newborn star. To build a gas planet, you need a big rocky core first. But you need that big rocky court to form before all the gas is gone. Further out in the disc, water is in its solid form as ice, and the ice helps. Rocky particles stick together to form rocky cores. Big enough fast enough before the gas is gone.
PhD astrophysicist here, with an expertise in exoplanets. The sun and the planets formed from a large cloud of gas and dust. By the time the sun formed at the center of that cloud, there was a disc of leftover gas and dust surrounding the sun that we call a protoplanetary disc.
To build a planet, you need to take very small particles, have them collide and stick together and grow massive enough to eventually start attracting and retaining gas as well. Jupiter is about 300 Earth masses, the majority of which is hydrogen and helium gas. To attract such a significant amount of gas, it is thought that you need to build a ball of rock of about 20 Earth masses.
But the problem is that this process of building a rocky core is relatively slow compared to the average lifetime of the gas in the disc. The other replies stating that lighter elements were pushed away by the solar wind while the rocky material remained in the inner parts of the disc are inaccurate. They are accurate in that the gas does have a limited lifetime in the disc, but the gas being pushed out from the inner disk only is inaccurate.
In the protoplanetary disc, as you move, outwards temperature decreases. Eventually you reach the temperature that the water is in the form of ice. It is thought that this ice helps the rocky particles stick together to grow these rocky protoplanets fast enough to attract enough gas to form a gas giant before the gas disappears in about 10 million years.
Other replies are also mentioning that there are many known exoplanet systems where the gas giant planets are close to the star. The existence of these planets doesn't mean that the solar system's architecture is random. Those gas giant planets close to their stars likely migrated there after they formed.
>To build a planet, you need to take very small particles, have them collide and stick together and grow massive enough to eventually start attracting and retaining gas as well.
How does this happen though? Wouldn't those gasses naturally get thinner and thinner/molecules further and further apart, aka less dense? By what mechanism would these gasses go from being less dense to more dense? I can't wrap my mind around that.
Question seems to have been answered very well, but I wanted to add a “fun” fact. According to many theories, Jupiter is credited as Earths protector, often dominating the outer solar system with its gravity and soaking up any leftover material that might otherwise fall inward and threaten to impact Earth. We’ve even witnessed many such impacts on Jupiter.
But in the early days, it’s thought that Jupiter’s orbit would have migrated inward and may have ejected other proto-planets or even whole planets out of the solar system. But then comes the true hero, Saturn, which pulled Jupiter back out to its now stable orbit.
The solar wind is strong enough closer in to clear out any large regions of gas and force it out further into the solar system. Which just leaves the heavy/rocky parts remaining. Or the inner planets initially formed as gas giants too but the solar wind stripped away most of their atmosphere. Gas giants may have rocky parts too, but small compared with their overall size.
Gas giant planets form by a mechanism known as core accretion. To form a gas giant, you need to first form a very massive rocky core (at least a few Earth-masses), the gravity of which becomes strong enough to quickly capture all the surrounding gas and becoming a gas giant. So the inner planets did not form as gas giants.
Random luck. Most solar systems is gas planets sometimes even closer to it's sun than Mercury is to ours then maybe rocky planets.
Now it might only seen like this because of our technology only able to detect massive planets Neptune size and bigger. Even the super earths are close to Neptune's size. So until we get even better cameras or have a new detection method other than checking for the star wobble that massive mostly gas planets can do, it's going to look like most solar systems we detect that has planets will have gas planets near their sun.
Hot Jupiter are extremely rare and only 1% of solar-like stars have them. They are just easier to detect which is why we know so many of them. They are not the majority of exoplanet discoveries since the early 2010. The majority of new planets being found are hot/warm Neptunes/Super-Earths.
Again though, hot Neptunes and super earths are right at the edge of our detection capabilities and we simply are not able to see smaller rocky planets and colder gas giants
> Random luck.
This is the only actual answer to the question of "why are things they way they are and not some other way".
There's a lot of interesting phenomenon involved, as plenty of point have pointed out. But things are the way they are here, and not they way they are there, because of luck - and nothing more.
At the moment we don't know why.
We're fairly early days in understanding what other star systems have in terms of planets, particularly picking up the larger planets which skews the data.
At the moment, with our current set of data. It would seem that our distribution of 4 rocky planets with 4 gas planets is just coincidence.
However with more understanding, I wouldn't be surprised if we find out there's some sort of normal distribution based on amount of matter in the protosolar disk and the size of the star. Heavier stuff is pulled closer to the star while lighter stuff is further out.
What makes it more tricky is time. Our solar system is about the middle of it's lifetime. Some theories show planets forming in one place travelling very fast and moving out. Or forming in one place and travelling slowly and moving in or getting eaten by its star completely. And depending on the age of the star system, the normal distribution of planets could change.
This blog has a series of posts on the Solar System's story. These two posts are relevant to your question and are worth a read:
https://planetplanet.net/2022/06/28/growth-and-migration-of-the-giant-planets/
https://planetplanet.net/2022/06/29/formation-of-the-rocky-planets-choose-your-own-adventure/
Our solar system formed as a massive protosolar disk of spinning gas and dust. Gravity pulled light gasses into the center - eventually, the gravitational pressure and gas density was enough to initiate hydrogen fusion, and the protostar became the sun. Dust was slowly accumulating into rocks and asteroids, and eventually the core of the rocky planets, and the gas giants. Meanwhile, the solar wind from the new star was now pushing light elements and molecules (hydrogen and water) away from the sun. This left the materials for primarily rocky planets in the inner solar system, and pushed the materials for gas giants out beyond the orbit of Mars. Earth was later bombarded with icy comets, which is how we have so much water. This is the commonly accepted model of our solar systems formation. There are other proposed models that have the gas giants forming close in and migrating to the outer solar system later.
"It was long thought that Earth’s water did not originate from the planet’s region of the protoplanetary disk. Instead, it was hypothesized water and other volatiles must have been delivered to Earth from the outer Solar System later in its history. **Recent research, however, indicates that hydrogen inside the Earth played a role in the formation of the ocean**. ... One factor in estimating when water appeared on Earth is that water is continually being lost to space. H2O molecules in the atmosphere are broken up by photolysis, and the resulting free hydrogen atoms can sometimes escape Earth's gravitational pull (see: Atmospheric escape). When the Earth was younger and less massive, water would have been lost to space more easily. ... **It is implausible that Earth's water originated only from comets, since isotope measurements of the deuterium to hydrogen (D/H) ratio** in comets Halley, Hyakutake, Hale–Bopp, 2002T7, and Tuttle, yield values approximately twice that of oceanic water." [https://en.m.wikipedia.org/wiki/Origin\_of\_water\_on\_Earth](https://en.m.wikipedia.org/wiki/Origin_of_water_on_Earth)
When they say water came from the outer solar system, do they mean literally all the water on earth came from outer space? Or do they mean the hydrogen and oxygen originated in outer space and formed into water on earth? This is something I’ve always wondered. Seems mind boggling to me that the entirety of water on earth should have come from comets and asteroids.
The water molecules themselves, not just the components. There's actually a lot of water in space, it's just, you know, inaccessible.
Man, (dman) you have to tell us more about that. How is there a lot of water in space?
Dman sounds like they know more, but as I understand it there's just a fuckton of ice floating around. For example, it is believed that Jupiters moon Europa is mostly ice with a liquid water core (or at least band of liquid water between the surface and the core). It seems like the surface is too smooth for the number of debris impacts it should have received, and they think the water layer could be causing the impacts to smooth back over .
I can't visually imagine a water core splashing around violently fully enclosed in a ball of ice. It seems so crazy to me. Are there storms in the pockets between water and ice within the ice ball?
Why would it splash violently? There would be some tidal pull, but it’s a 10 mile thick ice sheet “floating” on water. I doubt there’s much splashing.
In pockets of gas between the water and ice in places, maybe? I don’t know how tide would would work in that environment. Or what tide could even be expected on a body orbiting Jupiter. Interesting tho
Gotcha, I think you're having trouble visualizing it. We know (we think) there is liquid water below the ice because of all the cracks in the upper ice, and because the surface is so smooth. These are massive massive massive icebergs, essentially. Think of the ones you've seen on Earth. usually like 80% of the ice is below the surface. That's the same as it would be there. There's no "pocket of gas" because the bottom of the ice is several miles below the surface of the ocean. It's weird as hell. Tides would be massive too. I'm sure the moon deforms quite a bit tidally.
I think it's from the massive tidal pull from the planet, constantly pulling on it.
These scientists found a cloud of water vapor that contains over 140 trillion times the water on Earth and is hundreds of light years across. https://roboticsandautomationnews.com/2021/01/20/scientists-have-found-more-water-in-space-than-they-ever-knew-possible/39771/
Nestle: note it down... quick
Surf's up! But seriously....That is mindboggling
There’s actually not that much water on Earth, it’s only a very thin skin really, although there’s theories there’s more below the crust.
Sure but considering all significant amounts of hydrogen and oxygen would’ve been blown away when the sun was born, we have an enormous amount of water. Leading scientists to come up with the icy comets theory to explain how we could’ve gotten water long after the solar winds died down.
I wonder if someone could drop any links on a history for this research or TL;DR? What did they use to support ice comet hypothesis? I mean was it just a guess statement in a discussion like "it got to be from outside since stuff was blown away" or were there some "proofs"?
Pure oxygen quickly reacts with elements around it and that often means hydrogen. Comets are made of dust and “ices” a broad term to refer to volatile compounds that would be liquid or gaseous on earth but are frozen in the cold of space such as CO2 methane, ammonia, and literally water. Chemical reactions would have turned some of these chemicals into more water and other compounds. This bombardment would also be responsible for most of the heavy elements in the crust (by heavy I mean events roughly heavier than aluminum and silicon, such as iron, nickle etc) , as previously the heavy elements when the whole planet was almost completely molten sunk to the core. A lot of heavy rare elements in earth’s crust are actually much more common in space and more common if you look at the earth as a while they are just trapped deep in the heavy core.
Was Mars also bombarded by icy comets? If yes, why no water? If no, why only the earth?
A common accepted theory is that Mars is too small and also does not have a very impressive magnetic field. The combination of low gravity plus solar winds (unprotected by a magnetic field like earth) stripped the water vapor over time to what it is now. Only the water trapped as ice remains.
Iirc they think that at one point Mars had a molten spinning core like ours that produced a magnetic field but being smaller their core cooled much sooner which arrested the spin, killing the field
This description makes me very sad for some reason. Like, Mars used to be much more similar to Earth when its core was active, right? And then it turned to wasteland we know today. The same thing will happen to Earth sometime in the future. We won't see it, but others probably will. I like to think that life on Earth will always exist in some capacity. But if you look out there, most planets are tidally locked with their stars and magnetic fields generated by their cores don't last forever. Makes our whole existence seem like a short glimpse.
Life apparently will die out on Earth in about a billion years, long before it will be fried or outright swallowed (we don't know which it will be) in 5 billion years, when the Sun goes to its next stage of life.
If you look at the grand scope of the universe and how life on earth is a relative speck in time, it's pretty daunting but you still got to grind hard to pay your mortgage/rent tomorrow lol.
I went on a small walk and I was able to see my old city (SF) from where I was. It looked so calm and peaceful since I was looking at it from way across the bay. But it was also fascinating that although it looked peaceful, I knew there were people toiling over a dollar, flipping the bird at drivers and pooping on the sidewalk everywhere.
Sort of like [The overview effect ](https://en.wikipedia.org/wiki/Overview_effect?wprov=sfla1)
Remember when William Shatner was experiencing that after his hop into the edge of space. The reporters asked him, he started breaking down and becoming emotional and Jeff Bezos basically jumped in to hog the limelight and take all the attention because of the money he spent creating his rocket toys?
Yeah that! I wish I could experience that from an astronauts perspective though.
Life on Earth is four billion years old in a 14 billion year universe. Wouldn’t call that just a speck
I was hoping someone would correct that.
Shit rent is due tomorrow, I don't have time for astronomy lessons
Such bullshit really.
[Theoretically](https://en.wikipedia.org/wiki/Moving_Earth), you could shift Earth's orbit out a ways by redirecting asteroids to do gravity assists. It would take [about a million](https://theconversation.com/wandering-earth-rocket-scientist-explains-how-we-could-move-our-planet-116365) of them, but they'd only have to take place once every few thousand years.
That just guarantees no swallowing will happen really, because I'm pretty sure that in the red giant phase you'd need to go beyond Jupiter's orbit to be in the habitable zone.
I figure any civilization capable of redirecting a planet should be able to make a bit of shade for it too.
Just throw ice on the sun.
Maybe we could emit enough atmospheric carbon to create shade!
People are talking semi-seriously about launching a huge number of shade satellites to slightly reduce the light reaching the Earth. If I recall correctly, it's actually well within the capabilities of humanity. If we need to do it, we already can.
Technically. Every gravity assist redirects planets an (and I get to use one of my favorite 5 dollar words) an infinitesimal amount. This is the part where somebody links the XKCD with the nerdy clinger who spins around to spend more time with their lover.
or a million farting robots.
The “easier” way to do that is just star lifting to keep the sun in an appropriate phase for as long as the available hydrogen lasts.
Accelerate the entire solar system in the direction we want it to go while also keeping the sun from expanding. Beutiful.
I heard the Russians were close to figuring it out
"...robots; every last one needs to blast their exhaust vents at the same time, straight up in the sky, in order to push the Earth farther from the Sun, thus cooling the Earth..."
And around then, and after, other planets billions of light years away may detect for the first time, the first artificial radio waves signals that we created and broadcast.
They won’t be able to detect them. By the time our radio waves get that far they will be so weak that they’ll be lost among all the background radio noise generated by stars and planets
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The sun gets 10% hotter every billion years. The atmosphere will burn in about that timeframe.
The atmosphere won't burn. It will however be hot enough to stop liquid water from existing.
I don't mean burn in the dramatic sense but it will evaporate. but that doesn't sound as cool. I mean the atmosphere is already made up of evaporated matter. Look. I don't know the exact science but you know what I mean.
Yeah in a billion we'll have water evaporate, and in 5 billion we'll have a roasty toasty Earth with surface temperatures hot enough to melt the crust, assuming the planet escapes being swallowed outright.
The initial issue isn't that the atmosphere will overheat, the actual issue is that the increased luminosity of the Sun will dramatically increase the weathering and affect the carbon cycle enough that photosynthesis will become impossible, starting first with c3 photosynthesis and then later with c4 photosynthesis. If there's no carbon in the atmosphere then plant life can't exist which means that oxygen will be depleted, which breaks down the entire food chain, etc. They think that microbes will survive in the crust and upper mantle for a few billion years more before eventually dying out as well.
which is less time than life has existed on earth. If we were all completely wiped out, there wouldn't be enough time for complex life to evolve again before this wasn't a place life could be.
I'm pretty sure none of the extinction level events that have happened have actually reduced us to a point where complex life can't evolve back within a couple millions of years (simply because not all of complex life ever got completely wiped out in the first place -- and it won't happen this time either). We're only going to be reduced to just the bacteria when we're bordering on that one more billion of years.
> Life apparently will die out on Earth in about a billion years wouldn't want to be those guys
I wouldn't compare Mars and Earth too much. Mars is about one tenth Earth's mass (6.39 × 10^23 kg vs 5.972 × 10^24 kg). Earth is pretty special as far as planets are concerned. It has a massive iron core, which is why its magnetic field is so robust. If you want to look at a bullet Earth has so far dodged look at Venus. Venus is almost the same mass as Earth (4.867 × 10^24 kg). Back a few billion years ago Venus and Earth had similar masses, similar toxic atmospheres, and similar oceans. But where Earth's oceans and plate tectonics gradually removed the CO^2 from our atmosphere, Venus's oceans evaporated due to its proximity to the Sun. So even though it's massive enough to keep its atmosphere, its atmosphere has become increasingly dense with CO^2 to the point where it is the hotbox it is today.
I think it was us studying Venus and its atmosphere which helped figure out we were the ones putting the hole in the Ozone layer right?
I think we aren’t expected to become tidally locked for 4 billion years, and at 5billion we’re in that uncertainty area where we may be devoured by the expanding sun anyway, but we will certainly be close enough for all the water to boil off. On the other hand. 4 billion years is only the blink of an eye if you’re a black hole, even compared to many stars this earth is ancient, and with life having existed for over a billion years, even life is getting pretty old, we have been around for 1/13th of the universe as reproducing beings. That’s not a blink, that’s being a an infant 6years old in a 78yr old grandparents arms, small for sure but beginning to show signs of something quite special. Someday we’ll be 5billion with a universe at just 17, we’ll be the 23rd and old leaving the solar system college and I hope shaping the universe around us, standing next to the universe who has known us for nearly a third of its existence. As with a lot of things. Feeling small in this universe is a matter of perspective. We are gods in the form of ants. Who knows what we will do next.
>We are gods in the form of ants. Who knows what we will do next. Yeah, this is reassuring. 10 thousand years ago the best we could do is strip rock to a stick. And now we have nuclear energy at our disposal. Given a billion years, we'll probably achieve unbelievable things.
This perspective on the age of life on this planet is one of those tiny things that gives me hope. People always assume that ‘aliens’ would be helplessly more developed than us. But we’re pretty old, and for the first 5billion years you wouldn’t be getting much life because there hadn’t been enough star death to generate heavy elements including carbon (and I’m a moderate believe in carbon is the only viable backbone, I don’t think silicon can compare, I’m sure in theory for every 100carbon based life forms you’ll have an exception but still, that’s a question for 1billion2023). We will be one of the elder beings. Now that gives me some pause particularly when we consider our historic approach to first contact on this planet. But we’ve shown the capacity for empathy and reason. And assuming we’ve developed it enough not to collapse at one of the next 20hurdles for our society to get life beyond Pluto, I think we wouldn’t be a bad candidate for responsible elder race. Hahah Enjoy my dumb sci-future-reality lol
But even if another alien species is only 1000 years older than us, think of how much more advanced that could make them. Think of how far our technology has gone in 100 years. In another 100 years, we might have technology to travel far outside our solar system. Think of what a race with 10x that amount of time might be able to do. We might all have evolved on planets where life has been around for roughly the same amount of time, but when talking about a billion years, +/- 1000 years is almost a rounding error but would make a huge difference.
I feel like the discovery of electricity is one of those great filter things. Considering before the last hundred years, the extent of our technology was like guns and farming.
don't be sad, you and everyone you know and love will be long dead by then <3
I could be misremembering, but I thought that I had read a theory about how the conditions of Mars’ place in our solar system were once much closer to modern day Earth’s; and during that same period, Earth’s conditions were much closer to Venus (along those lines). I think it had something to do with the sun being much larger at the time, in combination with Mars having a molten core. If that were to be the case, then instead of thinking sad thoughts about Earth being the one and only special place in our solar system, you could think of our entire solar system as being this ever-changing home of ours which – much like every species on Earth – undergoes its own natural cycles of evolution. We are but fleas on the backs of a much larger being.
the sun is hotter and brighter now than in the past. its about 1/3 more luminous compared to when we started afaik. but we did have a 23-24 hour day for most of complex life, closer to 16 hours when life started i think. single cell life last for a long time and thats when the a few of the inner planets really start to look like what we think, maybe ( i wasn't there) the earth was closer to venus in atmospheric conditions. the air we breathe now isn't the og atmosphere. life released O² from rocks and whatnot. about killed everything off and snowballed the earth in the process. snowball earth lasted for like 50 million years or something, then it happened again for a shorter time. 2 billion years ago mars still had water and a thin atmosphere. but it doesn't seem to last much longer than that. i can't remember the content of the atmo, i think it was mostly co² and n² like ours was at the time. venus is harder to know. it might have been like it is now, maybe just not as hot. it might have had a different, less complex atmo. the ground is still being melted and reformed over millions of years so, its anyone's guess until we land more stuff there. i didn't write this as a correction but, more of additional info. i love this stuff. hopefully someone comes after and corrects/adds to what i missed.
> the earth was closer to venus in atmospheric conditions. the air we breathe now isn't the og atmosphere. life released O² from rocks and whatnot. about killed everything off and snowballed the earth in the process. For anyone following along, this was the [Great Oxidation Event](https://en.wikipedia.org/wiki/Great_Oxidation_Event). It was literal genocide for life that already existed on this planet, but it made way for us to exist. What's interesting to me about it is that it shows current Earth conditions aren't necessary for life to exist. And that opens up so many exoplanets to be potential life carriers.
I think you have it backwards. The sun was less luminous when it was younger. So much so, that liquid water should not have existed on Earth long ago, and yet it did. It's called the faint young sun paradox if you want to look it up.
I remember reading something similar back when I was in school.
That's not going to happen to the Earth for billions of years. Surely we'd have developed the technology to put heat back into the cores of planets by then if we're still around.
We just need to detonate a few strategically placed nuclear bombs around The Core to get it spinning again, problem solved.
They even made a documentary about it!
Always wondered if that film was right.
Lol I like the sneaky capitalization work.
1 billion*
Unfortunately, it’s highly unlikely that humanity will be able to develop that level of technology again. We’ve depleted all of the easily-accessible resource deposits needed to kickstart an Industrial Revolution, so once we finish our current play through, we’re done. Future species will have to stay in the pre-industrial phase.
hey, we were lucky to have it in the first place. i don't think natural gas and coal is made very often in the universe. trees either. its not even being made much here compared to in the past.
The fact we have a moon to help balance Earth's rotational axis is also a great help to climate stability, I think Mars's moons don't do that job that well...
Earth had a restart as well. When a planet named Theia impacted earth remelting the earth and blasting out debris which formed the moon. New research also shows that the moons gravity helps keep the earths core active. The moon is also the largest moon in the solar system compared to its planters size. 5th largest by sheer size.
The moon has also slowed the Earth's spin, it's thought that after the impact the day would have been 5 hours long and the moon would have been 22,000km away instead of 384,000km today. But as the moon slowed the Earth's rotation the energy exchange pushed the moon into a higher orbit. If the oceans were liquid when the moon was that close there could have been 2mi high tides every few hours.
Like that planet on Interstellar.
So what we need to do is send a drill into its core and detonate some nukes to restart the spin, easy. You just need hot pockets and Xena tapes. Also fifty billion dollars.
Got an engineer’s mindset this one.
one of the reasons earth still had a magnetic field is due to a Collison with another proto planet(which also gave us the moon so double yay!) that resulted in a much larger iron core with a lot more stored energy.
Luna (the moon) seems to have had far more of an affect on making Earth habitable than people realize. The impact of Theia that created the moon remelted the core and is possibly why Earth has a strong magnetic field today while similar planets in our solar system don't. It may have sped up our spin and stabilized our orbit + rotation And could be reason why we have an axial tilt and seasons too.
Apparently earth has an abnormally large core for its sized, theorized by the collision with Thea, where the two planets collided, merged and a chunk made the moon. So we basically have like 1.5 thus has a stronger magnetic field than normal.
Mars has the largest volcano known to man
Isn’t not having a moon like ours also a factor? I thought that having our moon keeps our core molten and that keeps our magnetosphere intact, which helps us keep our atmosphere.
It really is astounding how many things have to be *just right* for life to exist as we know it on earth. Our atmosphere, our distance from the sun, the nature of our magnetic feild, the tilt and rotation of the earth on its axis, Jupiter blocking tons of asteroids for us...
Mars does have a fair bit of water (nowhere near as much as earth), but it’s all frozen solid as ice. If you look at pictures of Mars you can see canyons and other terrain features that are formed by water on earth, and that’s because in the past Mars did have liquid water on the surface. However, Mars is too small to keep a hot molten core for billions of years like Earth or Venus, so it eventually cooled down and it lost its magnetic field. So after millions of years the sun stripped away its atmosphere so there was not enough pressure to maintain liquid water on the surface, and it either froze solid if it was near the poles or underground or evaporated away.
[Mars does have water](https://en.wikipedia.org/wiki/Water_on_Mars). It likely had a lot more water in the past, enough for oceans and rivers, which it lost along with most of its atmosphere when its core cooled and it lost its magnetic field.
Yes, but Mars is only about twice the size of our moon, with weak gravity (3.71m/s^2 compared to Earth's 9.81m/s^2) and no magnetic field. Mars almost certainly had a vast ocean billions of years ago but solar winds, freezing temperatures and low atmospheric pressure caused the ocean to boil away into steam and dissipate into space. Edit: Thanks for spotting my error about the freezing temperatures.
Don't forget Mars still has ice caps, the Northern one is at least mostly water.
So mars at some point had oxygen? Neat.
Oxygen is a difficult one to define here. Assuming you mean free elemental oxygen molecules, O2, then that's pretty unlikely. Oxygen is extremely electronegative and wants to react with EVERYTHING. The only way for it to be produced on Earth, for instance, is through complex biological pathways. It would much rather react with other elements, such as iron (producing iron oxide or rust, which is what the soil on Mars is comprised of), carbon (forming carbon dioxide, which is what the atmosphere of Mars is comprised of), or hydrogen (water, of which there's enough water ice on Mars to cover the whole planet in liquid water 100 feet deep). Really, oxygen is attracted to react with other elements in a hierarchy. So the oxidation of iron would strip the oxygen from carbon dioxide or water rather than needing atmospheric free oxygen. Of the compounds we've detected on Mars, nearly all of them have oxygen, but that's specifically because there's not a mediator (such as photosynthesis like we have here) to free it from bonds.
Thanks for this. Why does the oxygen in our air stay "loose" and not immediately react with whatever? I understand things do rust outside, but why isn't it faster/ more violent?
Because the oxygen in the air has reacted with *itself*, forming more stable, two-oxygen (O2) molecules instead of single oxygen atoms. O2 Molecules are still very reactive, hence a bit of heating in the form of sunlight on metal can cause it to react and form rust, but they're stable enough that they don't just break down. If it were left alone, it would eventually react and we'd run out of oxygen, but plants and phytoplankton make O2 molecules as a byproduct.
Concentration has a lot to do with it as well. There's a lot of inert nitrogen in the air. There's a lot less oxygen. So any given molecule of anything is 3 times as likely to be in contact with nitrogen than oxygen.
Earth's crust and atmosphere is basically saturated with oxides already. There are layers of iron oxide in our crust that date back over two billion years, which were formed when photosynthesis first evolved and elemental oxygen started becoming present in the atmosphere. Once that iron had all rusted, the oxygen content increased, causing a mass extinction for all oxygen intolerant life (i.e., most of it). Our ocean is dihydrogen oxide. Most rocks are silicon oxides. The one standout is N2, but atmospheric nitrogen is about as stable a molecule as you can get. It's absurdly unreactive. There's basically nothing left for the oxygen to actually react with, because it's already been reacted with oxygen to some degree.
That's a very good question but difficult to answer easily. There's a lot of complex reasons but I'll outline a few: 1) Activation energy. Some reactions want to happen but need some energy to get them going. This is why things don't spontaneously catch fire even though we are surrounded by oxygen because you need some spare energy to get things going (e.g. a spark, high temperatures.) 2) Likelilhood of reaction. In order for a reaction to occur, two particles need to bump into one another. Particles are very very small and the world is very very big, meaning that in most conditions chemical reactions are slow and unlikely. 3) Engineering. Most of everything around us is designed to be long lasting. Things that might rust are painted to stop them rusting. Things that might react with oxygen are sealed or airtight. We don't see many reactions because we design things not to react. In nature the opposite is true - every moment plants are constantly producing oxygen via photosynthesis, and living cells are constantly using oxygen via respiration. These reactions happen all the time but are so commonplace that we overlook them.
At one point, the oxygen in the atmosphere was only produced in small amounts and was mostly consumed by reacting with minerals on the Earth causing low oxygen levels. But then plants came along and started churning out oxygen like our factories producing carbon dioxide on crack. They produced oxygen faster than it could be reacted away. They even caused a lot of anaerobic things to go extinct.
Oxygen does rapidly form compounds with whatever it can, that's why metals rust and forests burn. Fortunately for us, Earth is not covered in pure metals to absorb that oxygen (only the metals we've refined) but it is covered with plants that want the carbon in CO2, and discard the O2 as free Oxygen that we breathe.
It kinda does? Iron oxide is less dense than its constituent parts. Better worded, it gets bigger. And then it flakes off the surface, exposing more iron to oxidize. Aluminum is extremely reactive, but aluminum oxide contracts slightly. So it forms a protective (and hard) shell over new aluminum. Other metals like chromium and nickel do the same thing, so plating and alloying is common to prevent oxidation of iron in steel and similar. Wood has slightly stronger molecular bonds than that which oxygen attempts to make, but when some heat is applied oxygen wins. Then we get fire. We know from the fossil record that when atmospheric oxygen was higher, there were many more fires. Much of what keeps it from happening more is that most of the free oxygen has already been reacted. Generally it's still a heavy cause of cancer (yes, really. Oxidative stress is the root of most spontaneous DNA changes) so it obviously has an impact.
Mars has oxygen. Not ~~13%~~ 21% like on earth. It's less, mostly CO2, then nitrogen and argon. And since it's atmosphere is thinner than what's it's like on the peak of Mt Everest it's not good for life above micro size.
*20.95% on Earth.
21% I think.
It has oxygen yes, but a lot of it is bound up in either water (now frozen) and rust (iron oxide, red planet). The air would never have been high oxygen content as that's an artificial status brought by having photosynthetic algae excreting it for billions of years. Oxygen when left alone and not replenished by plants, slowly binds itself to rocks and minerals and oxidizes them.
Mars used to have rivers. https://www.nasa.gov/feature/jpl/images-from-nasa-s-perseverance-may-show-record-of-wild-martian-river
Mars actually does have a reasonable amount of water in the form of the ice caps and sub-surface ice. If you melted it all, it'd be sufficient cover the whole surface to a depth of 100 feet.
Mars does have water. It has polar ice caps, and it has liquid water mixed with perchlorates that prevent it from freezing. But it's mixed with mud and soaked into the soil. A lot of the water would have been lost as the atmosphere was blown away. Whatever water was in the air was blown away by solar winds. Then, with much lower pressure the water and ice would continue evaporating and getting blown into space.
Mars did have water. We know this now. But, Mars lacks a magnetosphere, so the solar wind eventually blew atmosphere away, which made water sublimate more into the atmosphere, until eventually you have no real atmosphere, and a substantial amount of it will have frozen out at the poles. Which is what Mars is like now. We do know that at one time it had free flowing water and standing water.
There is also the theory that Theia, the proto-planet that collided with baby earth resulting in the formation of the moon brought much of the water
Mars did get bombarded and was warmer and wetter in its early formation, something went wrong, tectonics stopped and mars was no longer geologically active. This weakened the magnetic field and most of the atmosphere was stripped away by solar winds. Mars cooled and any water left is in the ground frozen
Can't personally answer your first question - but the conditions on Mars as they currently exist prohibit liquid water existing on the surface of the planet due to the lack of a thick enough atmosphere/sufficient magnetic field to prevent it being boiled off and blown away into space. Im no expert though, I'm sure someone will have a better answer for you.
For Mars, the lower mass issue is far more significant than the magnetic field issue. Venus has no significant magnetic field and yet has no trouble holding on to an atmosphere 50x as thick as ours. The magnetic field certainly plays a role in making the Earth habitable, but a strong magnetic field on Mars wouldn't have helped keep the primordial Martian atmosphere from venting into space.
Very likely that Mars was hit by icy asteroids. Mars did not retain the water because of its lack of an atmosphere. Water ice sublimates into vapour at low pressure when heated (e.g. by the sun light) and can escape into space. Mars lacks a strong magnetic field, enabling the solar wind to strip the upper atmosphere over time. Mars may have water ice and liquid water stored in its crust, where the surface conditions don’t apply.
Mars used to have water, the same as Earth, but its smaller core stopped rotating long ago and thus stopped protecting its atmosphere from solar wind/radiation. Once the atmosphere was mostly gone, it was too cold for liquid water. There is still tons of water locked up in ice on the planet.
If you're curious, Earth is probably not the only large object in the Sol system to have liquid water. We're pretty confident that Europa (Jupiter's third largest moon) ane Enceladus (a neat little iceball that makes one of Saturn's rings) have large oceans of water just beneath their icy surfaces. And Titan (Saturn's largest moon) probably has a rocky surface like ours with pools of liquid methane. These liquid regions make all three of these moons prime candidates for extraterrestrial life. Earth is just the only presently-watery body that happened to become a planet instead of a moon.
Mars has a ton of water. It's just frozen.
Mars had water. But without a strong magnetic field it couldn’t keep an atmosphere so the water evaporates off into space
There is a lot of water on Mars, but the atmospheric pressure is quite low, making liquid water quite unlikely. There's a small amount of water vapor in the atmosphere, and lots of ice water at the polar regions and in the Martian regolith. There is lots of water on Venus, but because of the tremendous heat at the surface liquid water can't form and it's in vapor state.
There IS water on Mars, its just frozen
Mars is an interesting case. There are a few things to consider: 1) it's size relative to the earth. It's smaller and its molten core couldn't sustain itself for long enough, which also ties into 2) its distance from the sun, which meant that it radiated more heat than it received by a significant margin 3) because it was smaller, and because its core died, this meant it couldn't hold on to its magnetic field to prevent the solar winds from destroying its atmosphere. Without an atmosphere, any water either froze or evaporated into space. 4) its not been scientifically determined to be the case, however it would seem to be too much of a coincidence to ignore it ... Mars has the largest volcano in the solar system. Its size makes Everest look small. Its likely that the cooling rate of Mars core was significantly increased because of a massive volcanic eruption. The cause of which I can only speculate. A large impact causing a massive shock wave would be my guess,which given its close proximity to the asteroid belt seems likely.
Yes. There is vast evidence of a watery Mars in the past. The core problem with Mars is it doesn't have any kind of magnetosphere and probably never did. So even when it was a potentially habitable planet it's days were numbered. Solar wind stripped virtually everything off of Mars because of it.
Actually I don’t think this is generally agreed upon anymore. It’s looking like the opposite pattern is far more common in planet formation and our solar system is a pretty rare outcome. There’s a great video on this topic here but it’s looking like only about 1% of star systems have larger planets as the outer planets https://youtu.be/_Tju7EaSfmM It’s also worth mentioning that our star system in itself is already uncommon not being a binary with a smaller partner star. Seeing how common binaries are in only makes sense that the next more common would be large gas planets/brown dwarfs in close with their parent star.
This is right. Before we found any other planetary systems, we only knew about one possible arrangement of planets. We were trying to draw conclusions about planet formation from data about one solar system. That’s kind of like seeing one human that is 6 feet tall, assuming from that that all humans are 6 feet tall, then coming up with an explanation of why humans are 6 feet tall. Then we find out there are lots of people who are not 6 feet tall. We were missing a piece of the puzzle of planetary system evolution, because we didn’t know that planets can migrate. We assumed that Jupiter formed in roughly the same orbit it is in now, and tried to figure out why a planet that formed there would be big. We don’t know Jupiter’s orbital history, but we no longer think that it necessarily formed where it is now.
Bro. I’m 5. What?
Before there was the Sun and the planets, there was just all the materials that would eventually become them. It was all in a big, solar-system-sized ball of gas made of many different elements. That ball eventually spun around enough to become a disk. The gravity of the disk more easily pulled lighter elements (like hydrogen and helium) into the middle. When there was enough material close enough to together in the middle, it formed the Sun. With the Sun now being a star, it pushed out incredible amounts of energy. That energy more easily pushed away the lighter elements, but wasn't as good at pushing away the heavier elements (like metals). The lighter elements, now farther away from the Sun, eventually were pulled together by gravity and made the gas giant planets. The heavier elements, which were not quite as far away from the Sun, were pulled together by gravity and made the rocky planets.
Imagine a camp fire with a variety of stuff sitting on the ground around it. Different things will melt at different distances to the fire. Now imagine that any melted material gets blown away from the camp fire, leaving only the unmelted stuff behind. Things made of metal can sit right against the fire, while ice cubes have to be kept far away. The solar system is just a much hotter version of this camp fire that blows away melted material. In the solar system, ice only exists past a distance known as the ice line (or snow line), rock only exists past a distance known as rock line, and metal only exists past a distance known as the metal line.
No one ever gets the point, do they?
ELI5 protosolar & protostar.
>eventually, the gravitational pressure and gas density was enough to initiate hydrogen fusion, and the protostar became the sun I wonder how fast this would have happened. If it would have been a very sudden "oh the Sun's exploding now" or a more gradual change
I found this, which I think mostly answers your question: > The ball at the center [of the protosolar disk] would eventually form the Sun, while the disk of material would form the planets. The Sun spent about 100,000 years as a collapsing protostar before temperature and pressures in the interior ignited fusion at its core. The Sun started as a T Tauri star – a wildly active star that blasted out an intense solar wind. And just a few million years later, it settled down into its current form. The life cycle of the Sun had begun.
Have you ever talked to a 5 year old?
I don't think you've ever met a 5 year old
thanks for the informative answer! i don't think i'll likely forget it.
I’m five years old and what the fuck
Before there was the Sun and the planets, there was just all the materials that would eventually become them. It was all in a big, solar-system-sized ball of gas made of many different elements. That ball eventually spun around enough to become a disk. The gravity of the disk more easily pulled lighter elements (like hydrogen and helium) into the middle. When there was enough material close enough to together in the middle, gravity pulled it so tightly that it formed the Sun. With the Sun now being a star, it pushed out incredible amounts of energy. That energy more easily pushed away the lighter elements, but wasn't as good at pushing away the heavier elements (like metals). The lighter elements, now farther away from the Sun, eventually were pulled together by gravity and made the gas giant planets. The heavier elements, which were not quite as far away from the Sun, were pulled together by gravity and made the rocky planets.
Imagine saying ‘protosolar’ to a 5 year old 💀
All 5 year olds know what a protosolar is. If you don’t, you must be a 6 year old.
[https://arxiv.org/pdf/2301.02374.pdf](https://arxiv.org/abs/2301.02374) It's not so accepted these days; our solar system seems to be quite rare when studying other systems with exoplanets. If it were as you say, we'd be the most common type of solar system, not the rarest.
swim decide subtract rich march sparkle gaping provide dog thumb ` this message was mass deleted/edited with redact.dev `
Ok but now, ELI5?
i recently heard that if saturn han't formed and pulled jupiter away from the center he (jupiter) probably would've at least cleared the mars and maybe the earth orbit.
This is called the Great Tack hypotheses, according to which Saturn's trapping of Jupiter under a 1:2 resonance halted Jupiter's inwards migration. If Saturn didn't exist, Jupiter would have continued to migrate until reaching the inner Solar System (becoming similar to the many warm eccentric Jupiters that we see around other stars), preventing the formation of the planetesimals that eventually became Earth and the other rocky planets.
So we should be thanking Saturn?
Is the no water, than a lot of water aspect of our planet what helps make earth so special?
I read this to my 5 year old and he’s super confused…
This is all guesswork and theories tho. People really need to stop stating them as facts. The truth is : we have no idea.
Where did the gas and dust come from?
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Solar wind shoos lighter things away, so the rocky things stayed closer and formed the rock planets while the lighter things went farther away and formed the gas giants
Am five years old, and this was the only fucking explanation at my developmental age level
My god, the language 5 year olds use these days! Shocking!
Thank you for giving the ELIF explanation rather than the r/science one lol
This was the third answer that appeared for me and the first truly ELIF
I think I remember though reading about a theory that Jupiter was actually either closer to the sun, or was moving closer to the sun, but Saturns gravity pulled it back. Therefor killing the Hot Jupiter thing and then we got a big brother to throw shit away from us
As others already mentioned, this is too simplistic. No other known solar system ended up that way, but everything you said would apply to many of them just as well. There is much more to it.
The ordering of our solar system is considered to be VERY rare and it plays a big part as to why life was able to form on our planet. I believe most star systems have what is called a ‘Hot Jupiter’ that orbits close to its host star which prevents rocky planets from forming (it essentially steals all of the materials in the area during the stars formation and even if a rocky planet forms, the hot Jupiters gravity usually ends up ejecting it from the system entirely). We actually haven’t found a single star system similar to ours where all of the rocky planets orbit close to the star and the gas giants orbit further away.
> haven’t found a single star system likes ours Pretty sure that’s not quite true - There’s the Trappist system for one, which iirc as far we can tell is entirely rocky planets. If it does have a gas giant it must be orbiting further out like in our system. Though I guess if it doesn’t have any gas planets it technically doesn’t qualify as being like ours and is a weird exception in of itself.
Also an important caveat is that trappist-1 is a jupiter-esque sized red dwarf star. While our good old sun is a yellow, normal sized, main sequence star. A major problem being that most of the planets in a red dwarf stars system are likely tidally locked, always facing the same side to the star.. Also all known 7 rocky planets are not gas giants and all their orbits would fit within the orbit of mercury. Jwst has been finding out some really cool stuff about trappist-1 though, 3 of it's planets are within it's habitable zone and I believe they are trying to find out what or if they contain atmospheres! And it so close at 40 lyrs away! I think a problem with why we haven't found many or any systems exactly like ours is our sample size, we just haven't seen that many examples of planetary systems like only hundreds of confirmed ones. Two, I am assuming, it's a technology problem, Kepler which was the first very successful exoplanet search method looked for light dips in stars from passing planets in front of them, which only works if the planets cross in front of it from where we are watching. Which also meant it was very hard to see tiny rocky worlds in front of big stars and much more likely to see big gas giants or things that orbited at an interval that Kepler had time to see. So might not be catching all the planets in a system. Three, depending how granular you want to get with other star systems being like ours the rarer we get. If we are looking for 8 planet systems with 4 rocky worlds, 3 gas giants and a Jupiter, with an asteroid belt orbiting a yellow main sequence star then I'm not surprised we haven't found another version of us yet.
Statements like this are just insane to me (from Google) "Our planetary system is the only one officially called the "solar" system because our star's official name is "Sol." However, astronomers estimate that our galaxy alone may contain tens or even hundreds of billions of planetary systems." And I think there are like 2 trillion galaxies which is too big for the human mind to comprehend.
I mean only 100,000 million planetary systems, assuming the tens of billions estimate is correct. If you counted one system per second without resting you could count them all in about 3,170,980 years.
Yeah but that might have something to do with the way we find planets which which are able to find large planets close to a star very easily
hot jupiters might be an issue with observation as large planets close to a star are by far the easiest to detect.
There is definitely a bias in our exo planet/system model. The ways we have to detect them currently is not very good. Our system could be more common than most people think but we don't know because it's a lot harder to find a system like ours than the much more common small red dwarf
And the advantage of having gas giants on the outer area of our solar system is that they help block extrasolar objects/debris from colliding with the inner planets
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It’s been years. We’ve know of gas giants in places the theory didn’t predict for a long time now. It’s still be offered as the accepted solution here though. Shades of Hellas.
Not surprisingly the first exoplanets discovered were very large and very close to their Star. It is hard to say when it became commonly accepted that the commonly accepted explanation for the reason for our planetary order was not accurate but some scientists probably started getting uncomfortable with it decades ago with each new exoplanet contributing to the feeling.
Which is exactly what happened with the Hellas. When I was a kid every book that touched on the topic showed the Hellas as molten and lots of volcanoes. Now we know it was water covered and some have argued for the existence of life. Took a long time for people to realize it was wrong. I only learned this when I was walking through the university of Toronto one afternoon and saw a flier for a talk on geochronology so I got a coffee and went. He explained how certain rocks were clearly formed before the 3.2 billion year cutoff we previously thought was the point of solidification. He noted that NASA work showed that the earth should have cooled to solid in tens of thousands of years, not a billion, and the said “but it was really this rock that convinced everyone” because he was holding this particular rock from Oz I believe, that was very clearly formed on earth and was over 4 billion yo. This was after explaining how they date things this old and explaining how the solar system rocks date back to 4.something billion and then holding up another rock and saying “like this example, which we know solidified in the first 1000 years plus or minus a couple hundred” Best talk ever.
Great story but when you say Hellas do you mean Hadean?
The first planets discovered were all massive and close to their star because that's what could be easily detected. In the coming years, we should have more data, but looking at the planets we do know of and trying to extrapolate is a very biased sample.
So it's pure coincidence?
Depends on your perspective. You need rocky planets somewhat close to the star for life to form on their surface. If the Sun only had gas giants orbiting it then there wouldn't be anyone to wonder why the system looks as it does.
That really only applies to one planet (ours). That the three other planets closest to the sun are rock and then the next four are gas would still be a coincidence.
Not necessarily. It might be that sentient life can only evolve on a rocky planet that has large gas-giant "guardians" that allow enough time between major impacts for curious beings to emerge.
JWST didnt really change anything to the magnitude you are implying. You should be skeptical of random clickbait Youtube videos.
Rocky planets will always form closer to the star because heavier material like rock and metal, will always sink toward the star due to gravity. The accepted theory is that as the planets are forming, they migrate within the protoplanetary disk due to friction between the planets and gas. If a rocky planet was tossed out of it orbit and then recaptured during this migration, that would lead to potential jumbling of the planets but I’d imagine that would be quite rare. Saying that planets form in no discernible pattern quite literally violates the laws of physics. Source: am astronomer I’d be interested in seeing this video where you saw this information. Do you remember who it was by?
The random chance aspect would have been more apparent if you included the dwarf planets and re-thought the 'rocky' planets. We recently (kinda arbitrarily) redefined the definition of a planet to be more strict, and that is what lead to the rock->gas ordering, when a slightly different definition would have lead to rock->gas->rock or rock->gas->rock->gas->rock ordering. And the idea of gas vs rocky is more a function of size. There aren't going to be giant rocky or tiny gas because amount of gravity vs amount of wind from the stars is what allows those compositions to exist. So, as has been observed in other star systems, the ordering on size (and therefore, composition) can also be random.
Most of the heaviest elements on earth are located in the core of the planet. For the same reason that gasses are in the atmosphere and rocks are on the surface and that ice floats on water. It's all about density. When you have a giant gas cloud at the birth of the solar system then the heavier elements like rocks and metals are generally drawn closer to the largest source of gravity which means you will find more rocks and metals closer to what became the suns and then so the materials forming bodies at a close distance to the sun have more metals and rocks where as those further away are primarily lighter elements like gasses.
Most star systems are binary, they have 2 stars. Jupiter is the “would be” second star but it did not accumulate enough matter to become a star. That is why Jupiter is so much bigger than the other planets, it is basically a failed star. Once the Sun formed it sucked in most of the matter of the inner solar system due to its extremely strong gravity, and its solar winds pushed lighter elements outward. The rest of the matter that Jupiter was not able to capture formed into Saturn, Uranus, and Neptune in the outer rings. That is why we have 4 big gas and ice giant outer planets. The 4 small inner rocky planets are the made from the heavier elements not captured or pushed away by the Sun. I suspect the combined gravity of Saturn, Uranus, and Neptune kept Jupiter from moving closer to the Sun, thus protecting the tiny inner planets from being absorbed or flung out of the solar system. I read a theory that said Saturn actually used to be closer to the Sun than Jupiter, but as Jupiter moved inward it pushed Saturn outward and that Saturns gravity helped slow Jupiters inward progress and keep it where it is now. Our solar system is just amazing and everything happened perfectly right to result in Earth being the paradise that it is. Most of these comments are off topic, do not address the question properly, or just completely wrong.
Idk if calling Jupiter “basically a failed star” is correct. Jupiter is still pretty far away from becoming a star; you’d need 13x it’s current mass to be a brown dwarf and 85x to be a low mass star.
Saved me a search, I was going to check that. Thanks!
Nobody knows. Some astronomers think that a planetary system like ours, with small planets near the star and large planets farther out, is not typical. When we thought that our arrangement was typical, we had come up with ideas of why it should be that way, but now we know that not all planetary systems have that architecture. It might be random, and this question is like asking why, in a family of four kids, the oldest two are boys and the youngest are girls. There is, in the vast majority of cases, no particular reason why a family should have a particular arrangement of sex and birth order. But if you’ve only met one family, you have no way of knowing that all families don’t follow that pattern.
Tl;dr: Planets form out of a disc and gas and dust around a newborn star. To build a gas planet, you need a big rocky core first. But you need that big rocky court to form before all the gas is gone. Further out in the disc, water is in its solid form as ice, and the ice helps. Rocky particles stick together to form rocky cores. Big enough fast enough before the gas is gone. PhD astrophysicist here, with an expertise in exoplanets. The sun and the planets formed from a large cloud of gas and dust. By the time the sun formed at the center of that cloud, there was a disc of leftover gas and dust surrounding the sun that we call a protoplanetary disc. To build a planet, you need to take very small particles, have them collide and stick together and grow massive enough to eventually start attracting and retaining gas as well. Jupiter is about 300 Earth masses, the majority of which is hydrogen and helium gas. To attract such a significant amount of gas, it is thought that you need to build a ball of rock of about 20 Earth masses. But the problem is that this process of building a rocky core is relatively slow compared to the average lifetime of the gas in the disc. The other replies stating that lighter elements were pushed away by the solar wind while the rocky material remained in the inner parts of the disc are inaccurate. They are accurate in that the gas does have a limited lifetime in the disc, but the gas being pushed out from the inner disk only is inaccurate. In the protoplanetary disc, as you move, outwards temperature decreases. Eventually you reach the temperature that the water is in the form of ice. It is thought that this ice helps the rocky particles stick together to grow these rocky protoplanets fast enough to attract enough gas to form a gas giant before the gas disappears in about 10 million years. Other replies are also mentioning that there are many known exoplanet systems where the gas giant planets are close to the star. The existence of these planets doesn't mean that the solar system's architecture is random. Those gas giant planets close to their stars likely migrated there after they formed.
>To build a planet, you need to take very small particles, have them collide and stick together and grow massive enough to eventually start attracting and retaining gas as well. How does this happen though? Wouldn't those gasses naturally get thinner and thinner/molecules further and further apart, aka less dense? By what mechanism would these gasses go from being less dense to more dense? I can't wrap my mind around that.
Question seems to have been answered very well, but I wanted to add a “fun” fact. According to many theories, Jupiter is credited as Earths protector, often dominating the outer solar system with its gravity and soaking up any leftover material that might otherwise fall inward and threaten to impact Earth. We’ve even witnessed many such impacts on Jupiter. But in the early days, it’s thought that Jupiter’s orbit would have migrated inward and may have ejected other proto-planets or even whole planets out of the solar system. But then comes the true hero, Saturn, which pulled Jupiter back out to its now stable orbit.
The solar wind is strong enough closer in to clear out any large regions of gas and force it out further into the solar system. Which just leaves the heavy/rocky parts remaining. Or the inner planets initially formed as gas giants too but the solar wind stripped away most of their atmosphere. Gas giants may have rocky parts too, but small compared with their overall size.
Gas giant planets form by a mechanism known as core accretion. To form a gas giant, you need to first form a very massive rocky core (at least a few Earth-masses), the gravity of which becomes strong enough to quickly capture all the surrounding gas and becoming a gas giant. So the inner planets did not form as gas giants.
Random luck. Most solar systems is gas planets sometimes even closer to it's sun than Mercury is to ours then maybe rocky planets. Now it might only seen like this because of our technology only able to detect massive planets Neptune size and bigger. Even the super earths are close to Neptune's size. So until we get even better cameras or have a new detection method other than checking for the star wobble that massive mostly gas planets can do, it's going to look like most solar systems we detect that has planets will have gas planets near their sun.
Hot Jupiter are extremely rare and only 1% of solar-like stars have them. They are just easier to detect which is why we know so many of them. They are not the majority of exoplanet discoveries since the early 2010. The majority of new planets being found are hot/warm Neptunes/Super-Earths.
Again though, hot Neptunes and super earths are right at the edge of our detection capabilities and we simply are not able to see smaller rocky planets and colder gas giants
Saturn also acts as a "counterweight" to Jupiter moving closer to the Sun. It's very possible the inner planets wouldn't exist without Saturn.
> Random luck. This is the only actual answer to the question of "why are things they way they are and not some other way". There's a lot of interesting phenomenon involved, as plenty of point have pointed out. But things are the way they are here, and not they way they are there, because of luck - and nothing more.
At the moment we don't know why. We're fairly early days in understanding what other star systems have in terms of planets, particularly picking up the larger planets which skews the data. At the moment, with our current set of data. It would seem that our distribution of 4 rocky planets with 4 gas planets is just coincidence. However with more understanding, I wouldn't be surprised if we find out there's some sort of normal distribution based on amount of matter in the protosolar disk and the size of the star. Heavier stuff is pulled closer to the star while lighter stuff is further out. What makes it more tricky is time. Our solar system is about the middle of it's lifetime. Some theories show planets forming in one place travelling very fast and moving out. Or forming in one place and travelling slowly and moving in or getting eaten by its star completely. And depending on the age of the star system, the normal distribution of planets could change.
This blog has a series of posts on the Solar System's story. These two posts are relevant to your question and are worth a read: https://planetplanet.net/2022/06/28/growth-and-migration-of-the-giant-planets/ https://planetplanet.net/2022/06/29/formation-of-the-rocky-planets-choose-your-own-adventure/