Over the last several months there have been numerous announcements of liquid water on Mars. However, researchers from the French national research institute CNRS announced that no water was found in the valleys that are carved in the slopes of the red planet. The researchers claimed that the Martian gullies were most likely formed by dry ice defrosting, according to a study.
"The role of liquid water in gully formation should... be reconsidered, raising the question of the importance of its occurrence in Mars' recent past," the researchers wrote in a news release.
Initially, researchers thought that the Martian gullies were the runoff melted water ice or groundwater leaks that took place hundreds of thousands of years ago. However, recently Martian gully formation was reported, even though the planet is too cold for liquid water to exist.
Francois Forget, a planetologist, and Cedric Pilorget, an astrophysicist, studied a thin layer of frozen carbon dioxide (CO2) which was said to be present in periods that gullies were being formed. The researchers used computer simulations, which showed that thawed and trapped CO2 gas that is accumulated under surface ice layer would eventually break through the soil and would release flows of gas and debris.
Pilorget claimed that dry ice melt does not result in all gully formation on Mars, however, cold areas with young gullies, the gassy theory "must be favored."
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