The layers of clay that in the past could have supported life on the surface of Mars would have been damaged by highly salty water, preventing the detection of possible signs of ancient living organisms on the planet, the authors of a study point out. published in the journal Science.
The researchers came up with this hypothesis after analyzing observations made by NASA’s Curiosity rover, which studies the bottom of the ocean. crater —And ancient lake— Gale since 2012. By taking two samples of sediment layers from 3.5 billion years ago, the apparatus discovered in one of them a concentration of clay minerals about two times lower than in the other, although they were collected only 400 meters away. Instead, that second sample contained high levels of iron oxides, the chemical compounds responsible for the color of the Martian surface.
According to the scientists, this composition may be due to the fact that the clay was destabilized and degraded by the brine that seeped into geological sediments after the lake dried up.
“We used to think that once those layers of clay minerals formed at the bottom of the lake in Gale Crater they stayed that way, preserving the moment of time when they formed over billions of years. But the later brines decomposed those clay minerals in some places, essentially resetting the rock record“quotes a release from NASA’s Jet Propulsion Laboratory to lead author Tom Bristow.
At the same time, the findings show not only the destruction of signs of a possible ancient life, but also point to the possible existence of organisms under the ground due to the action of groundwater that dissolve and transport chemicals, changing the structure of sediments. On Earth, that process, known as diagenesis, has created deep microbial habitats and could have done the same on Mars, scientists say.
For Bristow’s co-author John Grotzinger, deep biospheres “are great places to look for evidence of ancient life and measure habitability“.
“Although diagenesis can erase the signs of life in the original lake, it creates the chemical gradients necessary to support underground life, so we are very excited to have discovered this, “he explains.
The information obtained by Curiosity will be used in the future to choose the most promising rocks for possible traces of Martian life.
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