Martian gullies are formed by sliding blocks of dry ice
Scientists have just figured out that those winding gullies on Mars weren't carved by ancient rivers, but by blocks of carbon dioxide (dry ice) sliding down the dunes.
Utrecht University's Lonneke Roelofs and her team used Mars-like simulations in 2025 to watch how these icy blocks move and shape the landscape.
How does it work?
When Mars gets super cold (think -184°F), thick layers of CO2 ice build up on sand dunes.
As things warm up in spring, chunks break off. Gas builds up underneath and—boom—the blocks shoot forward, burrowing into the sand and carving out narrow gullies with raised edges as they go.
Why does it matter?
This flips what scientists thought about Martian gullies—turns out, it's not ancient water doing the work, but dry ice in action right now.
As Roelofs points out, studying weird processes like this on other planets helps us rethink what shapes landscapes here on Earth too.