these explorers grabbed some dry ice, which is basically super cold solid carbon dioxide, and took it to some sand dunes. They wanted to see what would happen if they let it slide down the slopes.
For reference, most sand dunes have a pretty steep angle, around 33 degrees. They tried regular ice and a block of wood first. The ice just melted and got the sand wet, and the wood barely budged.
With the dry ice, they thought it might move a little, but whoa, were they surprised! It just kept sliding and sliding all the way down the steep slope. It even worked on a much gentler slope on the other side! The only thing that stopped it was some bushes at the bottom.
Here's the cool science part: as dry ice warms up, it turns straight into gas, like skipping the whole liquid phase. This gas pushes against the sand, creating a kind of slippery layer. It's like the dry ice is riding on a tiny air cushion!
After a while, all that sliding actually carved out a little dip in the sand, almost like what you see on Mars! Apparently, carbon dioxide ice on Mars does something similar, slowly carving out channels as it moves.
