Environment & Science

Maybe Martian gullies weren't made by liquid water after all

Martian gullies on dunes in Russel Crater are partially covered by CO2 ice. Until recently they were thought to have been sculpted by flowing liquid water, but they may result from defrosting dry ice processes at the end of winter.
Martian gullies on dunes in Russel Crater are partially covered by CO2 ice. Until recently they were thought to have been sculpted by flowing liquid water, but they may result from defrosting dry ice processes at the end of winter.
NASA/JPL/University of Arizona

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Scientists have long wondered if there's flowing water on Mars and where it might be.

Sure, some features on the Red Planet are lined with gullies that look like ones carved by streams here on Earth, but modern Mars is too cold for liquid H20. What gives?

Maybe those gullies aren't the result of water after all, but rather stem from reactions caused by frozen carbon dioxide.

French researchers Cédric Pilorget with the Institut d'Astrophysique Spatiale and François Forget from the Laboratoire de Météorologie Dynamique examined this theory using a numerical model to simulate the environment on a Martian slope.

Ground there typically has top layer of dirt sitting on a bed of permafrost of frozen water. During the Martian winter, another layer of ice, this time made from carbon dioxide, forms on top of the soil. This makes a sort of ice, dirt, ice sandwich.

The researchers think that when the top layer of carbon ice starts to thaw in the spring, it gives off gas that fills that porous dirt layer in the middle.

This builds pressure and when the carbon ice finally cracks, that pressure releases, sending the gas rushing through the soil.

Martian Debris Flows

(How debris-flows looking like water-sculpted gullies can be triggered by dry ice processes on Martian slopes.)

This destabilizes the dirt and creates landslides with no water needed.

If the theory proves true it could mean the odds of flowing water on Mars are even slimmer than some think.