Rocks can tell us a lot about a planet. On Earth, the study of geology has been around for hundreds of years and has resulted in such scientific findings as the theory of plate tectonics and the discovery of dinosaur fossils. Geology on Mars has not had as long and storied a history, but with the rovers that have landed on the planet in the last few decades, Martian geology has started to bloom. Curiosity, one of those rovers, has done a particularly good job at documenting the rock formations in its neighborhood of Gale crater. Now researchers led by a team at Imperial College London have published a paper using data from Curiosity that detail a set of ancient dunes on Mars that provide some insight into the planet’s former habitability.