Scientists said evidence of ancient life on Mars has been 'erased,' as chunks of the Red Planet's rock record have been wiped by NASA's Curiosity rover. Hence, the team is looking for the missing items again.
In comparison to Earth, Mars has many ancient rocks and minerals. So scientists launched Curiosity to the planet's Gale Crater to learn more about its history.
For billions of years, the crater has been dry, and scientists have found evidence that supersalty water (brines) crept through fissures in the lake's bottom and changed the minerals beneath it.
Clay Minerals Gone? Iron Oxides Replace Minerals
Scientists analyzed samples taken from two places around 400 meters apart using the CheMin (Chemistry & Mineralogy X-Ray Diffraction) technique. Surprisingly, half of the clay minerals they expected to find in one location were absent, replaced by mudstones rich in iron oxides, which give Mars its red hue.
The rock record has most likely vanished as a result of saline water filtered through overlying sediment layers. Unlike the freshwater lakes that would have been there when the mudstones developed, the salty water most likely came from lakes that existed when Mars was drier.
"These are excellent places to look for evidence of ancient life and gauge habitability," said John Grotzinger, CheMin co-investigator at the California Institute of Technology. "Even though diagenesis may erase the signs of life in the original lake, it creates the chemical gradients necessary to support subsurface life, so we are really excited to have discovered this."
These findings, according to scientists, reveal the effects of Mars' eons-old temperature shift. Before the lakes in Gale Crater dried up, Nasa knew that groundwater had flowed beneath the surface, dissolving and burying compounds that scientists might analyze.
The mudstone changed after these minerals were deposited due to interactions with them, a process known as "diagenesis," which makes scientists' capacity to grasp the soil's earlier history more difficult or impossible. However, this also generates an underground environment that could support microscopic life, referred to as "deep biospheres" on Earth.
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"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," said Tom Bristow, CheMin principal investigator at NASA's Ames Research Center, in a statement. "But later brines broke down these clay minerals in some places — essentially resetting the rock record."
The scientists stated it was lucky that they could uncover both mudstones so close together because it allows them to use mineralogy to determine which parts of the Martian rock will help us find alien life and which will not.
NASA's Perseverance Mars Rover Starts Looking for Signs of Life
NASA's Mars 2020 Perseverance rover crew can utilize this information to evaluate and choose rock samples that could be returned to Earth. The Mars 2020 Perseverance rover from NASA has started looking for clues of ancient life on Mars. The rover tests the sensitive detectors it carries, obtaining their initial science readings, by flexing its 7-foot (2-meter) mechanical arm. The six-wheeled scientist will zoom in for closeups of tiny pieces of rock surfaces that might show traces of prior microbial activity, in addition to analyzing rocks with X-rays and ultraviolet light.
Abigail Allwood, the senior investigator at NASA's Jet Propulsion Laboratory in Southern California, said the rover's X-ray instrument called PIXL produced unexpectedly good science results while still being tested. The lunchbox-sized device, located at the end of the arm, fired its X-rays against a small calibration target aboard Perseverance. Its purpose is to verify instrument settings and detect the composition of Martian dust sticking to the target.
"We got our best-ever composition analysis of Martian dust before it even looked at rock," Allwood said in a NASA statement.
Early WATSON closeups have already given a plethora of data from Martian rocks, including a diversity of hues, grain sizes in the sediment, and even the existence of "cement" between the grains, scientists said. Details like these can reveal a lot about the formation process, water flow, and old, potentially habitable Martian ecosystems. They can also provide a larger environmental and even historical view of Jezero Crater when paired with PIXL.
The Mars 2020 Perseverance mission is part of NASA's Moon to Mars exploration strategy, which includes Artemis lunar missions to help prepare for human exploration of Mars.
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