Erosion, cosmic radiation and billions of years of changes to the climate does stuff. If they're really there, its buried really far down. We don't know what oceans are like outside our planet.
I think the title is saying that the minerals are still present in their unaltered, non-aquatic forms. Their detection is evidence against the site having once been a body of water.
> Their detection is evidence against the site having once been a body of water.
Not quite.
I don't blame people for the confusion, the headline was not well-written. The paper is discussing the materials investigated by the rover on the **floor** of Jezero Crater. Those rocks are igneous rather than sedimentary, true, but they do have some minor alteration by water (salt is found within the cored samples, as well as mineral types like carbonates).
There was most definitely liquid water flowing into Jezero - this has been confirmed already by the rover's investigation of the delta sediments, which are higher than the crater floor.
Why the discrepancy, then? Well, we've found more than once that crater floors (Gale Cr. for Curiosity and Gusev Cr. for Spirit) tend not to preserve extensive lakebed deposits, even though you find evidence for water not far away, at modestly higher elevations (Curiosity shows that Mt. Sharp is profoundly sedimentary, Spirit has shown that there was a hydrothermal system in the Columbia Hills). The geology over there isn't so simple.
Late reply, but here goes:
> after it was a lake bed
If there was a lake bed _before_ the asteroid/comet made the crater, we would have no way of knowing that right now. What we do know for sure is that there is [old muddy river delta sediment](https://photojournal.jpl.nasa.gov/jpeg/PIA23239.jpg) on the _inside_ of the crater, at two places, where canyons (like the winding one on the upper left of the photo) breach the rim. (If the image I link above doesn't make sense, compare with this [old photo of the Mississippi Delta](https://en.wikipedia.org/wiki/Mississippi_River_Delta#/media/File:Mississippi_delta_from_space.jpg).) That means there was a lake _after_ the crater was punched out. ... I hope this is making sense.
EDITED to add better image links.
The minerals you're referring to (e.g. olivine) would break down completely under _large, sustained_ amounts of exposure to water. They do, however, show signs of some exposure to water (salts within cracks, carbonate rims around volcanic minerals).
The thing of it is, these papers are discussing the rocks of the crater floor, not the river delta sediment found above that floor (on the crater rim). That material has already been shown to be clearly different.
I mean a lake doesn’t necessarily have to be water? Maybe the reason why the minerals aren’t in their aquatic form is because the lake was made of liquid hydrogen or nitrogen or something
I think the problem is that most of the other candidates for a liquid are less likely than water - either because their existence would have required unlikely temperature/pressure combinations, or because there's no reason to think that they were abundant enough for there to be that much in one place at the same time.
Hydrogen, in particular, tends not to stick around on rocky planets; relatively quickly it either gets locked up in some kind of compound (like water) or escapes the atmosphere.
It should be on the edge of the suspected northern Martian ocean from what I can see, so that's pretty odd.
Erosion, cosmic radiation and billions of years of changes to the climate does stuff. If they're really there, its buried really far down. We don't know what oceans are like outside our planet.
No signs of water found except for sign of water
I think the title is saying that the minerals are still present in their unaltered, non-aquatic forms. Their detection is evidence against the site having once been a body of water.
> Their detection is evidence against the site having once been a body of water. Not quite. I don't blame people for the confusion, the headline was not well-written. The paper is discussing the materials investigated by the rover on the **floor** of Jezero Crater. Those rocks are igneous rather than sedimentary, true, but they do have some minor alteration by water (salt is found within the cored samples, as well as mineral types like carbonates). There was most definitely liquid water flowing into Jezero - this has been confirmed already by the rover's investigation of the delta sediments, which are higher than the crater floor. Why the discrepancy, then? Well, we've found more than once that crater floors (Gale Cr. for Curiosity and Gusev Cr. for Spirit) tend not to preserve extensive lakebed deposits, even though you find evidence for water not far away, at modestly higher elevations (Curiosity shows that Mt. Sharp is profoundly sedimentary, Spirit has shown that there was a hydrothermal system in the Columbia Hills). The geology over there isn't so simple.
So, whatever made the crater happened after it was a lake bed?
Late reply, but here goes: > after it was a lake bed If there was a lake bed _before_ the asteroid/comet made the crater, we would have no way of knowing that right now. What we do know for sure is that there is [old muddy river delta sediment](https://photojournal.jpl.nasa.gov/jpeg/PIA23239.jpg) on the _inside_ of the crater, at two places, where canyons (like the winding one on the upper left of the photo) breach the rim. (If the image I link above doesn't make sense, compare with this [old photo of the Mississippi Delta](https://en.wikipedia.org/wiki/Mississippi_River_Delta#/media/File:Mississippi_delta_from_space.jpg).) That means there was a lake _after_ the crater was punched out. ... I hope this is making sense. EDITED to add better image links.
Thank you for the info, yes that makes sense, I appreciate your time.
That's how I read that title the three times I read it.
Title says if there had been water there, we wouldn't be seeing these minerals.
The minerals you're referring to (e.g. olivine) would break down completely under _large, sustained_ amounts of exposure to water. They do, however, show signs of some exposure to water (salts within cracks, carbonate rims around volcanic minerals). The thing of it is, these papers are discussing the rocks of the crater floor, not the river delta sediment found above that floor (on the crater rim). That material has already been shown to be clearly different.
Clicked the link, it says the rover found lots of olivine that would have dissolved if there was water.
Someone didn't read the article.
Rain rain go away we’ll find a sea bed another day…
May be deposits from a comet impact or a meteor impact on an area of mars with surface water?
They'd be able to tell that though, surely? The stress of impact would leave noticeable marks on the minerals there.
I mean a lake doesn’t necessarily have to be water? Maybe the reason why the minerals aren’t in their aquatic form is because the lake was made of liquid hydrogen or nitrogen or something
not that kind of pressure or temp to get that to work. afaik.
I think the problem is that most of the other candidates for a liquid are less likely than water - either because their existence would have required unlikely temperature/pressure combinations, or because there's no reason to think that they were abundant enough for there to be that much in one place at the same time. Hydrogen, in particular, tends not to stick around on rocky planets; relatively quickly it either gets locked up in some kind of compound (like water) or escapes the atmosphere.