New research from NASA scientists studying Mars could show that possible evidence of ancient life on Mars was destroyed in the planet's former lake systems.
Scientists have found new evidence that as the red planet's climate changed, super-salty water, or 'brines', seeped through the cracks of Mars' lakes and altered the clay mineral-rich layers underneath.
Clay minerals feature water in their structure and act as evidence that the soils and rocks that contain them were in contact with water at some point in history.
The new findings published on July 9 help scientists understand where the rock record preserved or destroyed evidence of Mars' possible signs of ancient life.
The breakthrough evidence was gathered mostly by the Chemistry and Mineralogy, or CheMin, instrument – aboard NASA’s Mars Science Laboratory Curiosity rover.
Tom Bristow, CheMin principal investigator and lead author of the paper at NASA’s Ames Research Center in California’s Silicon Valley, said: “We used to think that once these layers of clay minerals formed at the bottom of the lake in Gale Crater, they stayed that way, preserving the moment in time they formed for billions of years.
“But later brines broke down these clay minerals in some places – essentially resetting the rock record.”
Scientists decided that one of Mars' former lakes, the Gale Crater, was perfect for searching for evidence of the planet's history due its undisturbed layers of rocks.
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With the use of CheMin, scientists compared samples that were taken from two areas close to a layer of mudstone that had been deposited billions of years ago at the bottom of the lake.
Shockingly, around half the clay minerals they were expecting to find in one area of the crater were missing.
Instead they found mudstones rich with iron oxides, which give Mars its characteristic rusty red colour.
The minerals were around the same age and started out the same, which made the scientists question how some of the minerals could seemingly 'disappear'.
Scientist's compared the details of minerals found from both samples and concluded that salty water filtering through sediment layers was responsible for the changes.
Despite the freshwater lake that was present when the mudstones originally formed, the salty water is believed to have been from later lakes that existed in a drier environment.
The research findings show further evidence of the impacts of Mars' climate change billions of years ago, scientists say.
“We’ve learned something very important: There are some parts of the Martian rock record that aren’t so good at preserving evidence of the planet’s past and possible life,” said Ashwin Vasavada, Curiosity project scientist and co-author at NASA’s Jet Propulsion Laboratory in Southern California.
“The fortunate thing is we find both close together in Gale Crater, and can use mineralogy to tell which is which.”
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