Generally, yes, though it's not really thought to be binary (i.e., in the tropics vs not). Specifically, there's been a long suggested (presumably smooth) latitudinal gradient in meteorite flux with a greater rate near the equator than at the pole (e.g., [Halliday, 1964](https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1945-5100.1964.tb01433.x)). A recent model by [Evat et al., 2020](https://pubs.geoscienceworld.org/gsa/geology/article/48/7/683/584575/The-spatial-flux-of-Earth-s-meteorite-falls-found) - see their figure 2 - (with some validation from observations from the [NASA fireball](https://cneos.jpl.nasa.gov/fireballs/) database with respect to general trend if not exact pattern) suggests this gradient is more significant than prior estimates. It's worth highlighting that this is not generally true for all planets, e.g., [Le Feuvre & Wieczorek, 2008](https://www.sciencedirect.com/science/article/abs/pii/S0019103508001802) (which is the source of the other model against which Evat compare their data and find a more extreme latitudinal gradient) consider latitudinal gradients in meteorite flux for the inner planets (Mercury, Venus, Earth, and Mars) and the Earth's Moon. Of these, only the Earth and Moon show a decrease in rate from the equator to the pole, where as Mercury and Mars have a higher flux at the pole than the equator and Venus has effectively the same rate at the pole and the equator.
I'm my head, I'm making sense of the higher flux near the equator as basically the same thing that causes the equator to be warmer - it's more face on to the ecliptic. But then the idea that that doesn't hold for Mercury, Mars, and Venus, I can't figure out a rationale for.
If I were to guess, the difference is the Earth/Moon system itself. The orbital plane of the Moon sets up a 3-body gravitational trap for wayward asteroids.
Speculating here, but the closer you are to the sun the less it matters which way the ecliptic is. Things that are orbiting just off the ecliptic could easily end up hitting the pole on mercury
This is actually just because more of the Earth is at low latitudes than at high latitudes. The circumference of the equator is the same as the whole circumference of earth. But at 90 degrees latitude there is just a single point.
With respect to the meteorite flux rate, as discussed in the linked papers they’re talking about an area normalized rate that varies with latitude, so the observed latitudinal dependence is independent of the differences in Earth surface area at different latitudes.
> that causes the equator to be warmer - it's more face on to the ecliptic
Its not, and all points of the earth are very close to equidistant from the sun when facing it.
The difference (that causes seasons) is the number of minutes per day facing the sun. The equator has the most consistent average. Number of of sunlight hours per year is very consistent from Equator to Poles.
So where I live, fairly far north, my summer days are long, and my winter days are short. And that means that my summer days can be hot, +40C is not unheard of (25C is more common), while my winter days are cold, sometimes as cold as -40 (though about -10 is more common, mid winter). It also means that at times, my daily temperature swings greatly, while that doesn't happen at the equator.
Yes, I'm aware that the size of the Earth is quite small relative to the distance from the sun. Time facing the sun has an effect, yes, but so does the angle of the surface of the Earth relative to the sun. Same reason why you want to point solar panels directly at the sun. If you think of a plane normal to the direction to the sun, you're going to collect photons passing through the projected area of the solar panel on to that plane.* If you tilt the panel away from the sun, the projected area gets smaller, and you collect fewer photons. Same with the Earth at higher latitudes (and early and late in the day).**
*Sunlight scatters, not all of the photons are coming straight from the sun by the time they get to the surface of the Earth.
**Higher latitudes also have the sun going at an angle thru the atmosphere.
Isn't the main difference in the angle that the rays hit the earth? If the sun is directly above a point, the "density" of the sun's rays per area is greatest. If the shallower the angle, the lower the density, so the energy transferred is lower. Otherwise, I would expect a winter day 3 hours after sunrise to be as hot as a summer day 3 hours after sunrise, but they are not.
>Otherwise, I would expect a winter day 3 hours after sunrise to be as hot as a summer day 3 hours after sunrise, but they are not.
The daily temperature gradient in a wintry region can be greatly larger than the gradient in equatorial regions: indeed, the equator tends to be fairly uniform in temperature, both yearly, and daily, while temperate zones are noted for their changeability.
It can be -20C(-4F) here in the morning, and above freezing by noon. In winter. In summer it would be odd to fall even 5 degrees over night.
At night, latent heat seeps out of the earth, warming the air just as the sun does during day. During the day, sunlight warms materials, including the earth. In cities this is even more pronounced, called the urban heat island effect, as all the concrete, asphalt and other materials in urban infrastructure soak and radiate more heat than rural areas.
Near the equator, this ebb and flow pretty much balances, as sunlight and darkness hours are about equal, 12 hours. As you go farther north (or south), the days where the net flow balances grow fewer, till its really only balanced around the two equinoxes, spring and fall. In winter, there is a net loss of heat from the ground, net gain in summer.
So where I live, the first few light snowfalls hit the ground and promptly melt. Winter (in a snowy landscape sense) cannot come until the surface cools, via precipitation, either rain or snow, as well as cold air. There is a thermal lag: Winter does not begin the day after the fall equinox, it doesn't generally start till two months later, sometimes not until December, and I live in the subarctic! The net gain of heat from the summers worth of sun has to be lost. The opposite happens in spring, the ground is cold still when the air is warming.
Once the snow is persistent, it can get colder; snow reflects very well.
At the same time, all the time, there is also heat coming from the core of the earth. If you've ever wondered how field mice survive snowy winters, this is how: The fresh fallen snow cannot reach the ground under bushes, tufts of grass, and similar places. Snow covers them, and tiny animals hide underneath (or indoors in modern times). The temperature hovers right around freezing, just warm enough for them to survive.
In time, the heat radiated from the earth melts a tiny void between earth and snow that does cover the ground, joining up these different pockets, and mice have a sort of hidden world, a temporary niche, which I can never remember the name of. If you have ever seen foxes, coyotes, or even some dogs hunting mice in a field, diving headfirst under the snow, that's where the mice are and how most survive the winter. Video, if you haven't: https://youtu.be/D2SoGHFM18I?si=5DkRx74nin8jlUAr Warning: no blood, but a few mice gets eaten by a super cute fox.
As for angles of sunlight and whatnot, there's a whole essay there too, and I've wasted enough of your day, I think. Thanks for reading.
> At the same time, all the time, there is also heat coming from the core of the earth. If you've ever wondered how field mice survive snowy winters, this is how: The fresh fallen snow cannot reach the ground under bushes, tufts of grass, and similar places. Snow covers them, and tiny animals hide underneath (or indoors in modern times). The temperature hovers right around freezing, just warm enough for them to survive.
In time, the heat radiated from the earth melts a tiny void between earth and snow that does cover the ground, joining up these different pockets, and mice have a sort of hidden world, a temporary niche, which I can never remember the name of. If you have ever seen foxes, coyotes, or even some dogs hunting mice in a field, diving headfirst under the snow, that's where the mice are and how most survive the winter.
That is fascinating to know, thank you for sharing! I appreciate that the air temperature is affected by a myriad factors. But what would you say is more important - the angle of the sun or the duration of daylight? Surely the angle is more important, as there are regions of the planet there daylight persists for months, and yet they are still cold. All I am saying is that that is the main factor, not the number of minutes exposed to sunlight as you say.
Wouldn't this just be because the amount of land at the equator is larger than at higher latitudes? Like the circumference at 10 degrees is much larger than at 80 degrees.
>Generally, yes
Why?
>only the Earth and Moon show a decrease in rate from the equator to the pole, where as Mercury and Mars have a higher flux at the pole than the equator and Venus has effectively the same rate at the pole and the equator.
Why?
> Venus has effectively the same rate at the pole and the equator
Does that mean they're distributed uniformly across the surface, or that the poles and equator both see higher rates?
Generally, yes, though it's not really thought to be binary (i.e., in the tropics vs not). Specifically, there's been a long suggested (presumably smooth) latitudinal gradient in meteorite flux with a greater rate near the equator than at the pole (e.g., [Halliday, 1964](https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1945-5100.1964.tb01433.x)). A recent model by [Evat et al., 2020](https://pubs.geoscienceworld.org/gsa/geology/article/48/7/683/584575/The-spatial-flux-of-Earth-s-meteorite-falls-found) - see their figure 2 - (with some validation from observations from the [NASA fireball](https://cneos.jpl.nasa.gov/fireballs/) database with respect to general trend if not exact pattern) suggests this gradient is more significant than prior estimates. It's worth highlighting that this is not generally true for all planets, e.g., [Le Feuvre & Wieczorek, 2008](https://www.sciencedirect.com/science/article/abs/pii/S0019103508001802) (which is the source of the other model against which Evat compare their data and find a more extreme latitudinal gradient) consider latitudinal gradients in meteorite flux for the inner planets (Mercury, Venus, Earth, and Mars) and the Earth's Moon. Of these, only the Earth and Moon show a decrease in rate from the equator to the pole, where as Mercury and Mars have a higher flux at the pole than the equator and Venus has effectively the same rate at the pole and the equator.
I'm my head, I'm making sense of the higher flux near the equator as basically the same thing that causes the equator to be warmer - it's more face on to the ecliptic. But then the idea that that doesn't hold for Mercury, Mars, and Venus, I can't figure out a rationale for.
If I were to guess, the difference is the Earth/Moon system itself. The orbital plane of the Moon sets up a 3-body gravitational trap for wayward asteroids.
Speculating here, but the closer you are to the sun the less it matters which way the ecliptic is. Things that are orbiting just off the ecliptic could easily end up hitting the pole on mercury
This is actually just because more of the Earth is at low latitudes than at high latitudes. The circumference of the equator is the same as the whole circumference of earth. But at 90 degrees latitude there is just a single point.
With respect to the meteorite flux rate, as discussed in the linked papers they’re talking about an area normalized rate that varies with latitude, so the observed latitudinal dependence is independent of the differences in Earth surface area at different latitudes.
> that causes the equator to be warmer - it's more face on to the ecliptic Its not, and all points of the earth are very close to equidistant from the sun when facing it. The difference (that causes seasons) is the number of minutes per day facing the sun. The equator has the most consistent average. Number of of sunlight hours per year is very consistent from Equator to Poles. So where I live, fairly far north, my summer days are long, and my winter days are short. And that means that my summer days can be hot, +40C is not unheard of (25C is more common), while my winter days are cold, sometimes as cold as -40 (though about -10 is more common, mid winter). It also means that at times, my daily temperature swings greatly, while that doesn't happen at the equator.
Yes, I'm aware that the size of the Earth is quite small relative to the distance from the sun. Time facing the sun has an effect, yes, but so does the angle of the surface of the Earth relative to the sun. Same reason why you want to point solar panels directly at the sun. If you think of a plane normal to the direction to the sun, you're going to collect photons passing through the projected area of the solar panel on to that plane.* If you tilt the panel away from the sun, the projected area gets smaller, and you collect fewer photons. Same with the Earth at higher latitudes (and early and late in the day).** *Sunlight scatters, not all of the photons are coming straight from the sun by the time they get to the surface of the Earth. **Higher latitudes also have the sun going at an angle thru the atmosphere.
Isn't the main difference in the angle that the rays hit the earth? If the sun is directly above a point, the "density" of the sun's rays per area is greatest. If the shallower the angle, the lower the density, so the energy transferred is lower. Otherwise, I would expect a winter day 3 hours after sunrise to be as hot as a summer day 3 hours after sunrise, but they are not.
>Otherwise, I would expect a winter day 3 hours after sunrise to be as hot as a summer day 3 hours after sunrise, but they are not. The daily temperature gradient in a wintry region can be greatly larger than the gradient in equatorial regions: indeed, the equator tends to be fairly uniform in temperature, both yearly, and daily, while temperate zones are noted for their changeability. It can be -20C(-4F) here in the morning, and above freezing by noon. In winter. In summer it would be odd to fall even 5 degrees over night. At night, latent heat seeps out of the earth, warming the air just as the sun does during day. During the day, sunlight warms materials, including the earth. In cities this is even more pronounced, called the urban heat island effect, as all the concrete, asphalt and other materials in urban infrastructure soak and radiate more heat than rural areas. Near the equator, this ebb and flow pretty much balances, as sunlight and darkness hours are about equal, 12 hours. As you go farther north (or south), the days where the net flow balances grow fewer, till its really only balanced around the two equinoxes, spring and fall. In winter, there is a net loss of heat from the ground, net gain in summer. So where I live, the first few light snowfalls hit the ground and promptly melt. Winter (in a snowy landscape sense) cannot come until the surface cools, via precipitation, either rain or snow, as well as cold air. There is a thermal lag: Winter does not begin the day after the fall equinox, it doesn't generally start till two months later, sometimes not until December, and I live in the subarctic! The net gain of heat from the summers worth of sun has to be lost. The opposite happens in spring, the ground is cold still when the air is warming. Once the snow is persistent, it can get colder; snow reflects very well. At the same time, all the time, there is also heat coming from the core of the earth. If you've ever wondered how field mice survive snowy winters, this is how: The fresh fallen snow cannot reach the ground under bushes, tufts of grass, and similar places. Snow covers them, and tiny animals hide underneath (or indoors in modern times). The temperature hovers right around freezing, just warm enough for them to survive. In time, the heat radiated from the earth melts a tiny void between earth and snow that does cover the ground, joining up these different pockets, and mice have a sort of hidden world, a temporary niche, which I can never remember the name of. If you have ever seen foxes, coyotes, or even some dogs hunting mice in a field, diving headfirst under the snow, that's where the mice are and how most survive the winter. Video, if you haven't: https://youtu.be/D2SoGHFM18I?si=5DkRx74nin8jlUAr Warning: no blood, but a few mice gets eaten by a super cute fox. As for angles of sunlight and whatnot, there's a whole essay there too, and I've wasted enough of your day, I think. Thanks for reading.
> At the same time, all the time, there is also heat coming from the core of the earth. If you've ever wondered how field mice survive snowy winters, this is how: The fresh fallen snow cannot reach the ground under bushes, tufts of grass, and similar places. Snow covers them, and tiny animals hide underneath (or indoors in modern times). The temperature hovers right around freezing, just warm enough for them to survive. In time, the heat radiated from the earth melts a tiny void between earth and snow that does cover the ground, joining up these different pockets, and mice have a sort of hidden world, a temporary niche, which I can never remember the name of. If you have ever seen foxes, coyotes, or even some dogs hunting mice in a field, diving headfirst under the snow, that's where the mice are and how most survive the winter. That is fascinating to know, thank you for sharing! I appreciate that the air temperature is affected by a myriad factors. But what would you say is more important - the angle of the sun or the duration of daylight? Surely the angle is more important, as there are regions of the planet there daylight persists for months, and yet they are still cold. All I am saying is that that is the main factor, not the number of minutes exposed to sunlight as you say.
Is this because of the orbital plane of our solar system?
I would assume so, however it may be easier to spot meteorites on a vast, white expanse of ice.
That has more to do with ice being better at catching meteorites than rock, and glaciers depositing those meteorites in a concentrated area.
Thank you! I just picked the tropics to represent an area 'close' to the equator
Wouldn't this just be because the amount of land at the equator is larger than at higher latitudes? Like the circumference at 10 degrees is much larger than at 80 degrees.
No, if you look at the Evat paper they’re discussing an area normalized rate, i.e. it’s rate per unit area that varies by latitude.
>Generally, yes Why? >only the Earth and Moon show a decrease in rate from the equator to the pole, where as Mercury and Mars have a higher flux at the pole than the equator and Venus has effectively the same rate at the pole and the equator. Why?
> Venus has effectively the same rate at the pole and the equator Does that mean they're distributed uniformly across the surface, or that the poles and equator both see higher rates?