orincoro t1_j19v0c1 wrote

The wind has been found to generally uncover things from time to time. The soil on the surface is so dry and fine that it takes a very long time for dust sediment to “settle” or harden, as it would on earth due to moisture condensing from the air. Mars has very little frost, no significant organic decay of minerals, so there is not as much tendency for things to get buried.

Basically all that life and moisture on earth makes everything kind of sticky. Mars is far less “sticky.” Something can be covered up, only to be completely uncovered again as the wind continues.


orincoro t1_j19omuz wrote

But 15 meters a year is really, really fast. The rest of the world is moving like 5-6 cm a year.

I have a hard time believing that figure because this would imply that Australia has moved 750 kilometers north in just the time since humans lived there. That would be really surprising to me.

Edit: as I suspected, it moves more like 15 meters every century. Still extremely fast for a continent, but not 15 meters a year.


orincoro t1_iw6a5dw wrote

They use radio carbon dating of the sediment it was formed in. The sediment itself is formed from a mix of organic and inorganic material, including bacteria, or plant matter. Sometimes you find spores and seeds. The plant matter in the sediment can be accurately dated to when it stopped growing, because the carbon in it will begin to decay predictably at that moment.

So basically it’s the same as if you were studying a plant, but you’re relying on a relatively smaller sample size, and there’s some error because not all the organic matter dies at the same time. But it gives you a range that is pretty close, within a few thousand years.

(ETA: apparently not for things quite this old).