A recent study described the structure of organic carbon that NASA’s spacecraft discovered last year on the surface of Mars in sedimentary rocks that contain what could be a “biosignature” or a possible sign of the presence of microbial life in the past.

These clay rocks may have formed between 3.2 and 3.8 billion years ago under a body of water that has now disappeared in the “Jezero Crater” in the northern half of Mars.

Organic carbon can be used as evidence to reveal whether Mars has harbored life at any time in the past, because it forms the chemical basis of the molecules that make up DNA, cells, and proteins.

But its presence is not conclusive evidence of the existence of life, because it can also arise from non-biological processes such as the chemical reaction between rocks and water.

The discovery of organic carbon in two rocks in the Jezero crater, called (Chiava Falls) and (Walhalla Glades), was announced last year when researchers announced the discovery of what is likely to be a bio-signature in one of them.

Planetary scientist Ashley Murphy of the Planetary Science Institute in Arizona, one of the leaders of the new research published in the journal Science Advances, said that the rover took samples of the two rocks from two locations separated by about 100 meters.

Following the discovery last year, NASA published a picture of the Chiava Falls rock, showing very fine-grained mudstone in a rust-red color, with ring shapes resembling tiger spots, in addition to dark marks resembling poppy seeds.

Such features on Earth can be linked to microbial activity.

A potential biosignature or (bioindicator) is defined as a substance or structure that may have a biological origin, but more data or additional studies are needed before reaching a conclusion about the possibility of the existence of life or not.

Using the Sherlock device on board the Perseverance rover, researchers in the new study conducted a careful examination of the complex carbon, known as macromolecular carbon, present in the two rocks.

The researchers said that this carbon bears similarities to carbon formed through either biotic or abiotic processes on Earth, as well as to carbon formed through abiotic processes found in meteorites.

This is the first time that large molecular carbon has been discovered in clay rocks in Jezero Crater, where the Perseverance rover landed in 2021.