by ruidh » Wed Oct 31, 2007 3:53 pm
moshulu wrote:Something has always puzzled me about Martian craters. Given that they are very old, and that there is so much dust/soil all over the place, why aren't the craters filled to the rim?
Clearly, it's because the volume of dust on Mars isn't sufficient to fill all of the craters. And I'm not at all surprised that it isn't. Dust is made by the erosion of rock: wind erosion mostly, though some small amounts from freeze/thaw cycles near the poles and minute amounts from impacts. The more dust you have, the more it piles up on the surface and covers the rocks you need to make more dust. Eventually, the rate of dust production falls to a minimum and little more dust is produced.
Take a look at Victoria Crater which Opportunity is just entering, there's some dust pooling at the bottom of the crater -- the dunes are pretty obvious in the pictures, but, there's clearly not enough duct to fill that crater completely and the wind is strong enough to pull some out as it flows over the crater. The crater itself is likely in equilibrium -- filling and emptying at the same rate.
[quote="moshulu"]Something has always puzzled me about Martian craters. Given that they are very old, and that there is so much dust/soil all over the place, why aren't the craters filled to the rim?[/quote]
Clearly, it's because the volume of dust on Mars isn't sufficient to fill all of the craters. And I'm not at all surprised that it isn't. Dust is made by the erosion of rock: wind erosion mostly, though some small amounts from freeze/thaw cycles near the poles and minute amounts from impacts. The more dust you have, the more it piles up on the surface and covers the rocks you need to make more dust. Eventually, the rate of dust production falls to a minimum and little more dust is produced.
Take a look at Victoria Crater which Opportunity is just entering, there's some dust pooling at the bottom of the crater -- the dunes are pretty obvious in the pictures, but, there's clearly not enough duct to fill that crater completely and the wind is strong enough to pull some out as it flows over the crater. The crater itself is likely in equilibrium -- filling and emptying at the same rate.