A new theory from Brown University questions common ideas about clay on Mars, which is omnipresent on the Red Planet. Instead of forming through muddy interactions with lakes and rivers, like clay on Earth, Martian clay could have formed near the beginning of the planet's existence, when it cooled from a world with high volcanic activity and magma flow to a stable rocky surface.
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As the oceans of liquid magma cooled on the surface of Mars, water and other chemical compounds with low boiling points would have evaporated from the surface of the planet. According to the laboratory tests and computer models at Brown, this could have created an atmosphere that served as a "high-pressure steam bath". The thick atmosphere would have interacted with the newly formed surface, creating clay.
"The basic recipe for making clay is to take rock and add heat and water," said Kevin Cannon, a doctoral candidate at Brown who led the research. , in the press release. "This primordial atmosphere created by an ocean of magma would have been the warmest and wettest Mars in history, a situation where you could alter the crust and then simply mix those materials later."
Cannon and his associates, who published their findings in Nature, say that this theory shows how clay could exist on Mars without a complex hydrothermal system. The models of the study show that primitive Mars, after steam, was probably in a constant freezing state, one where it was very unlikely that there was much running water.
"One of the complications that arises in the evolution of Mars is that we can not create a scenario in which surface weathering has the capacity to produce the degree of mineral alteration we see," said Jack Mustard, Brown professor and co-author of the study. "Certainly, we are not trying to completely rule out other mechanisms of alteration.Surface weathering and other types of alteration surely occurred at different points in Martian history, but we believe that this is a plausible way of explaining much of the extended clay that we see in the older Martian lands. "
The Brown models estimate that the steaming Martian environment could have lasted as long as ten million years, long enough to cover the planet in clay. The team synthesized rocks with the same composition as Martian basalt and recreated simulating the supposed Martian atmosphere in a high-pressure chamber. Then they let him cook for two weeks.
"It was really remarkable how quickly and extensively this basalt was modified," Cannon said. "At the highest temperatures and pressures, it ate completely through the basalt particles, it's a really intense degree of disturbance."
If the theory holds, it would mean that there are large deposits of Martian clay below the surface waiting to be discovered. If the smoky atmosphere lasted as long as 10 million years, as Cannon and his co-authors predict, he could have created a layer of clay on the Martian surface up to three kilometers thick.
"One of the things I like about this is that it's really verifiable," says Steve Parman, a geology professor at Brown and co-author of the study. "With a sample returned, or perhaps even with the analytical equipment in a rover, I am optimistic that this primordial process can be distinguished from some other process of alteration."
Fortunately, NASA's Mars 2020 rover will include a drill that will collect samples and leave them aside, waiting for a future mission to collect them. Once these samples return to Earth, several questions about the past of the Red Planet can be answered.