A bizarre, spotted rock detected by NASA’s Perseverance rover could be new evidence that Mars was once home to microbial life.
The Perseverance science team dubbed the rock, which measures 3.2 feet by 2 feet (1 meter by 0.6 meters), Cheyava Falls. It was picked up on July 21 during the rover’s slow expedition of a region known as Neretva Vallis. The valley was home to liquid water billions of years ago when Mars was warmer and therefore a likely spot for life to have blossomed.
At first glance, the rock’s most distinctive features are long white veins of calcium sulfate and bands of what is likely hematite, an element that contributes to Mars’ red coloring. But when Perseverance zoomed in, there were dozens of off-white circles with black borders, each around a millimeter in width that NASA described as being “akin to leopard spots.” When Perseverance analyzed their chemical makeup, NASA scientists discovered that the black rings contained iron and phosphate.
“These spots are a big surprise,” said David Flannery, an astrobiologist and member of the Perseverance science team, in a statement. “On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.”
On our planet, the spots occur due to chemical reactions that turn red hematite rocks white, but also produce the black iron and phosphate rings. The reactions also release energy that microbes can feed on.
While Perseverance project scientist Ken Farley called Cheyava Falls “the most puzzling, complex and potentially important rock” yet found by the rover, he acknowledged that much about how it formed remains unexplained. One possibility is that the rock was initially mud containing organic compounds that eventually turned into rock. When fluid penetrated fissures in the rock, it brought mineral deposits that created the calcium veins and spots.
Another explanation comes from the presence of another mineral in Cheyava Falls: olivine, which forms in magma. That suggests Cheyava Falls’ spots may have come about due to a chemical reaction during a time when the area was heated to a temperature incompatible with life.
NASA scientists said they’ve done all they can to analyze the rock with Perseverance’s onboard instruments; further study would require bringing Cheyava Falls back to Earth. Now, the rover, which has become known for both stunning discoveries and juvenile humor, is continuing its exploration of Neretva Vallis. The space agency is currently aiming to send a crewed mission to Mars in the 2030s. However, given the frequent delays in its mandate to bring humans back to the Moon, this may not happen for quite some time.
