Sand Flows May Have Created Martian Gullies

For the past 11 years, ever since the Mars Global Surveyor spacecraft sent back images of the mid-latitude regions of the Red Planet, astronomers have been obsessed with the gully-like features they noticed in the datasets. The landscape features resembled their Earth-based counterparts significantly, and so experts naturally assumed that the formation process must be the same between the two. But a new study now seems to suggest that this is not the case, and that water is not responsible for the gullies on our neighboring planet, Technology Review reports.

Over time, various theories have argued that the gullies were not in fact formed by water, but by the flow of sand on the surface. Now, a series of experiments appears to validate this assumption and indeed verify that sand flows are responsible for carving out the landscape features. An additional element that seems to support this idea is the vast amount of data sent back by Spirit and Opportunity, the NASA rovers that are currently in their seven year on the planet.

While the new theory does nothing in the way of proposing that water never existed on Mars, it simply draws attention to a number of issues related to the age of the gullies. While the two exploration rovers indeed found signs of water on the Red Planet, the liquid was present at their respective locations billions of years ago, and not sooner. On the other hand, the gullies were found to be only a few million years old. This clearly eliminates the possibility that they were created by water. Some proposed that water from aquifers may be responsible, but the idea does not stand because rain is needed to replenish aquifers, and no such thing exists on Mars.

Scientists at the Universidad Nacional Autonoma de Mexico, led by experts Yolanda Cedillo-Flores and Hector Javier Durand-Manterola, propose a new explanation for the gullies. They say that the formations developed as frozen carbon dioxide in the ground started to sublimate into the Martian atmosphere. This process in turn makes the sand become “fluid,” and start “flowing” even above light slopes. This explanation also accounts for why no gullies exist at the equator or poles. Carbon dioxide cannot freeze at the equator, and cannot unfreeze at the poles, the experts say.