Evidence of ancient life on Mars was “lost,” scientists said, when NASA’s Curiosity rover discovered that parts of the Red Planet’s rock record had been lost.
Mars has a large amount of ancient rocks and minerals compared to Earth, and to gain more knowledge about the planet’s history, scientists sent Curiosity to the hurricane craters of Mars.
Craters have been drying for billions of years, and scientists have evidence that super-salt water (salt water) seeps through cracks in the lake floor, changing the minerals beneath.
Using the CheMin (Chemistry & Mineralogy X-Ray Diffraction) tool, the scientists compared samples from two areas about 400 meters apart. Surprisingly, they found that half of the clay minerals thought to exist in an area were missing; they have been replaced by claystone rich in iron oxide, which gives Mars its red color.
It is likely that the saltwater filtered through the overlapping layers of sediment is what caused the rock record to disappear. The saltwater may have come from lakes that existed when Mars was drier, as opposed to freshwater lakes that existed when mudstone formed.
“We used to think that this layer of clay minerals that formed at the bottom of the lake at Gale Crater stayed that way and continued to form for billions of years,” said Tom Bristow, CheMin Research Principal at NASA’s Research Center. , in a statement. “But the brines then mine these clay minerals in some places — and thus essentially restore rock records.”
Scientists believe these results show the effects of climate change on Mars that occurred thousands of years ago. NASA already knew that before the Gale Crater lake dried up, groundwater was already beneath the surface, dissolving and hiding chemicals scientists could study.
Once these minerals are deposited, the mudstones change due to interactions with them in a process known as “diagenesis”, which inhibits or obliterates scientists’ ability to understand soil history. However, it also creates an underground experience that can support microbial life – known on Earth as the “deep biosphere”.
“This is an excellent place to look for evidence of ancient life and measure habitability,” said John Grotzinger, a CheMin co-investigator at the California Institute of Technology. “Although diagenesis can erase signs of life in pristine lakes, it creates the chemical gradients needed to support life below the surface.
Scientists say they were lucky enough to find the two mudstones so close together because they were able to use mineralogy to determine which pieces of Martian rock are lighting up our search for extraterrestrial life and which are not.
This information can also be used by NASA’s Mars 2020 Perseverance rover team to evaluate and select rock samples that can be returned to Earth.
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