Scientists have long suspected deep trenches found on the surface of Mars were carved out by liquid water, similar to what we see on Earth. However, a new study reveals these gullies weren’t altered by water at all. So how’d they get there?
Researchers at Johns Hopkins University study images from NASA’s Mars Reconnaissance Orbiter to figure out how these gullies were formed and found that the surface hadn’t been altered in any way by liquid water.
Here’s how they were able to come to that conclusion:
The pictured area spans about 2 miles (3 kilometers) on the eastern rim of Hale Crater. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter took the visible-light image. Color-coded compositional information added in the lower version comes from the same orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
Color coding in light blue corresponds to surface composition of unaltered mafic material, of volcanic origin. Mafic material from the crater rim is carved and transported downslope along the gully channels. No hydrated minerals are observed within the gullies, in the data from CRISM, indicating limited interaction or no interaction of the mafic material with liquid water.
If it wasn’t liquid water, what was it? Researchers aren’t entirely sure, but they believe “a mechanism not requiring liquid water” is likely to blame. One theory is that the process of carbon dioxide frost thawing and freezing again over millions of years—and ongoing today—has something to do with it.