More than a decade ago, NASA’s Mars Global Surveyor returned stunning images of gullies shaped like water-carved streams on Earth, raising the prospect that Mars may be a friendly haven for life.
But appearances can be deceiving.
"When dealing with other worlds, we must take care to remember that unfamiliar processes are possible and even likely in alien environments," planetary scientist Colin Dundas with the U.S. Geological Survey in Flagstaff, Ariz., wrote in a commentary in this week's Nature Geoscience.
The gullies, which appear in slopes around the planet’s mid-latitudes, have been a puzzle because modern-day Mars is too cold to support the amount of surface water needed to carve the features.
Two French researchers believe they have the answer: seasonal pressure changes in pockets of dry ice trapped beneath the planet’s surface are periodically erupting, which disrupts the regolith and triggers debris flows.
The theory is not completely new, but Cedric Pilorget and François Forget, with the University of Paris-Sud, and Paris’ Pierre and Marie Curie University, respectively, flesh out the idea with some hard numbers.
“Dry-ice-related processes seem to have played a more important role in the evolution of the martian landforms than previously thought,” the researchers conclude in a study published in this week's Nature Geoscience.
“The role of liquid water in gully formation should, therefore, be reconsidered, raising the question of the importance of its occurrence in Mars’ recent past,” they said.
Originally published on Discovery News.
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