A Potential Biosignature has been Found on an Ancient Martian Rock

A potential biosignature indicating the presence of ancient lifeforms has turned up in a rock on the surface of Mars, in the form of what may be traces of chemical reactions from the life processes of ancient microbes. Although the sample will need to be returned to Earth to confirm whether or not there are microfossils present, this news adds more evidence to the potential that Mars may have been home to alien life.

Found by NASA’s Perseverance rover on the surface of a reddish rock called Cheyava Falls, these possible biosignatures appear in the form of millimeter-size white “leopard spots” that have been found to contain organic compounds by the rover’s SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) module. However, it is important to note that while carbon-based organic molecules are vital to the existence of life as we know it, these molecules are not necessarily indications of biological life, such as the vast amount of methane that is found in Jupiter’s atmosphere.

Additionally, the leopard spots are rimmed with black edges that contain iron and phosphate. Phosphate compounds are crucial for the formation of DNA, and are part of the makeup of adenosine triphosphate, or ATP, a compound responsible for transporting metabolic energy throughout the body.

“These spots are a big surprise,” according to David Flannery, an astrobiologist with the Queensland University of Technology in Australia, and member of the Perseverance science team. “On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface.”

Despite the distinctive markings appearing to match their biologically-produced counterparts that appear in Earth rocks, the Perseverance team cautions that it is still possible that there might be a non-biological source for these miniature formations.

“Cheyava Falls is the most puzzling, complex, and potentially important rock yet investigated by Perseverance,” explained Kenneth Farley, a Professor of Geochemistry at the California Institute of Technology, and project scientist for the Mars 2020 Perseverance rover mission.

“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,” Farley continued. “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.”

For instance, Cheyava Falls has also been found to contain olivine, millimeter-size crystals that are formed from magma, possibly formed at a higher elevation in the Neretva Vallis, a formation carved by an ancient river that flowed near Jezero Crater. The team is investigating the possibility that the olivine and sulfate were added to the rock by high temperatures that might have occurred during a geological event, such as a volcanic eruption or meteor strike, causing a non-biological chemical reaction that resulted in the leopard spots.

“We have zapped that rock with lasers and X-rays and imaged it literally day and night from just about every angle imaginable,” Farley remarked. “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.”

The rock sample taken from Cheyava Falls is the 22nd sample gathered by Perseverance since its arrival on the Martian surface in 2021; the cache of pencil-shaped samples is expected to be retrieved by a probe that will be part of the NASA-ESA Mars Sample Return mission, expected to deliver the first samples of Martian rock to Earth early in the next decade. Hopefully their successful return will answer the question of whether or not life arose while more favorable conditions were present on Mars in the Red Planet’s deep past.