An arrowhead-shaped rock on Mars sporting features that may hint at ancient microbial activity on the Red Planet has left scientists puzzled.
NASA announced in July of last year that the rock, found in Mars‘ Jezero Crater by the agency’s Perseverance rover, held some of the best evidence yet that ancient microbial life may have existed on the Red Planet billions of years ago, when it was significantly wetter than it is today. Earlier this week, scientists involved with the discovery presented their findings publicly for the first time this week at the Lunar and Planetary Science Conference in Texas, detailing the rock’s chemical signatures and structures that continue to offer tantalizing hints of ancient Martian microbial life.
The fine-grained mudstone named Cheyava Falls, after the highest waterfall in Arizona’s Grand Canyon, sits at the edge of an ancient river valley known as Neretva Vallis, which runs along the inner wall of the crater. The rock features spots of black, blue, or greenish hues, which the researchers have nicknamed “poppy seeds.” Alongside these are dozens of dark-rimmed, millimeter-size splotches dubbed “leopard spots.” Perseverance’s instruments have revealed that several rocks hosting these two features are rich in iron, but that they vary in their oxidation states and redness — a telltale sign of activity by organic matter, which may have bleached the rocks of their red color.
“On Earth, reactions like these are commonly associated with microbially-driven organic matter respiration,” Joel Hurowitz, the deputy principal investigator of the PIXL instrument located at the end of Perseverance’s robotic arm, said at the conference.
Back in July, the discovery team had also noted the presence of calcium sulfate veins running through the rock, suggesting that water may have once flowed through it. While this and other features could point to non-biological processes, such as exposure to high temperatures from a volcanic event, ongoing analysis suggests the rock was never subjected to such heat or exposed to heat-related processes that would have caused it to recrystallize. “Everything seems to be consistent with low-temperature processes,” Hurowitz said.
Scientists suspect the Neretva Vallis channel was carved out eons ago, by water gushing into the crater. One theory is that…
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