NASA’s Perseverance rover, which has operated on Mars since February 2021, recently found a large rock containing organic compounds that may have been microscopic life in the distant past. The results are as yet uncertain, so scientists are not ready to proclaim that life once existed on the Red Planet. The discovery came when the rover’s SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument scanned material from the rock.
The science team named the rock Cheyava Falls, after a waterfall in Earth’s Grand Canyon. Perseverance encountered it at the northern edge of Neretva Vallis, an ancient river valley that emptied into Jezero Crater billions of years ago. The rock measures 3.2 feet by 2 feet (1 meter by 0.6 meter). The rover took a core sample from it July 21.
Ancient leopard spots
“Cheyava Falls is the most puzzling, complex, and potentially important rock yet investigated by Perseverance,” said Ken Farley, Perseverance project scientist of Caltech in Pasadena, in a press release. “On the one hand, we have our first compelling detection of organic material, distinctive colorful spots indicative of chemical reactions that microbial life could use as an energy source, and clear evidence that water — necessary for life — once passed through the rock. On the other hand, we have been unable to determine exactly how the rock formed and to what extent nearby rocks may have heated Cheyava Falls and contributed to these features.”
The inside of Cheyava Falls features large white calcium sulfate veins separated by bands containing hematite, one of the minerals that gives the Red Planet its distinctive color. Perseverance also found dozens of tiny off-white splotches, each ringed in black, which look reminiscent of leopard spots. The rover’s PIXL (Planetary Instrument for X-ray Lithochemistry) instrument found that the black material contains iron and phosphate.
“These spots are a big surprise,” said David Flannery, an astrobiologist and member of the Perseverance science team from the Queensland University of Technology in Australia. “On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.”
The Perseverance science team thinks Cheyava Falls may have been mud with organic compounds mixed in that eventually turned into rock. Later, fluid penetrated the rock, creating the calcium sulfate veins seen today and resulting in the spots.
Answers remain elusive
“We have zapped that rock with lasers and X-rays and imaged it literally day and night from just about every angle imaginable,” said Farley. “Scientifically, Perseverance has nothing more to give. To fully understand what really happened in that martian river valley at Jezero Crater billions of years ago, we’d want to bring the Cheyava Falls sample back to Earth, so it can be studied with the powerful instruments available in laboratories.”
“We have designed the route for Perseverance to ensure that it goes to areas with the potential for interesting scientific samples,” said Nicola Fox, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington, D.C. “This trip through the Neretva Vallis riverbed paid off as we found something we’ve never seen before, which will give our scientists so much to study.”
