More than ten years ago, NASA’s Mars Global Surveyor space orbiter sent stunning photographs of ravines to Earth that looked so much like Earth’s ravines ravaged by Earth that it gave hope that Mars might once have been suitable for life.
But appearances can be deceiving.
A new study shows that the Martian ravines were rather cut up by frozen carbon dioxide rather than water.
“When exploring other worlds, we must accept the fact that unfamiliar geological processes can take place there,” said planetary scientist Colin Dundas of the US Geological Survey in Flagstaff, Arizona.
The ravines that formed on the slopes of the mountains in the middle latitudes of the planet were a real puzzle, because modern Mars is too cold to maintain enough water needed to form these features.
The ravines are relatively young, only a few million years old. Even more intriguing is the fact that the repeated series of images made by Mars Global Surveyor shows that some of the ravines have been formed these days. Two French researchers believe that they were able to answer this question: seasonal changes in pressure in the pockets of dry ice trapped beneath the surface of the planet cause a periodic eruption, disrupting the integrity of the regolith and causing mudslides.
The theory is not new, but Cedric Pilgoret and Francois Forgett from the University of Paris-Sud and the University of Pierre and Maria Cur in Paris, respectively, fleshed out the idea with some exact figures.
Their new computer model calculates seasonal changes and effects on the underlying layer of the regolith, a layer of carbon dioxide ice and carbon dioxide gas, which is located above. Modeling can take into account various latitudes, slopes and other parameters.
Scientists have discovered that most of the ravines could have been formed as a result of a process that does not require liquid water.
"The processes associated with dry ice seem to have played a more important role in the evolution of the Martian terrain than previously thought," scientists concluded in a study published this week in the journal Nature Geoscience.
“The role of liquid water in gullying should be reviewed,” they said.