Lynn Carter

So there was this period where a bunch of spiral troughs were formed and then for some reason they were topped over and filled in by new ice.

So we can see this history of how this polar cap evolved.

And further work with this has suggested that what's actually happening here is that you have these what are called katabatic winds.

So you have winds that come off the cap and they preferentially sublimate ice off one side and then it gets deposited onto the other side of this trough.

And that over time, if you keep taking the material off one side and sort of shoveling it onto another side using winds, you end up with a spiral pattern.

And so being able to find these buried ones

points to times when maybe the katabatic winds weren't functioning the same way that they were today or you had a climate shift that somehow caused a different type of deposition in the pole.

But this was one of the first clues that we had that you could actually look into the polar caps and see things that were buried that we didn't have any surface expression for.

So that's been pretty interesting for all of us.

Another thing that we found was that there are these really big CO2 deposits at the polar caps.

At the south polar cap, rather.

The polar caps mostly water ice.

People thought that there might be a little bit of CO2, maybe not very much.

There's certainly CO2 dry ice, effectively, that's deposited on the caps in the winter.

What they were surprised to find, though, is that there's actually a lot of CO2 ice on the south polar cap.

So using the radar, because the radar wave responds to compositions differently, then the radar picked up that there was this different composition at the polar cap.

And so here is a map showing some of the CO2 deposits and the thickness of these deposits.

So this reservoir of CO2, it's like 30 times larger than previously thought.

It's very young.

It's at the top of the layer, which means that it's young.