NASA study examines organic carbon found in ancient Martian rocks

WASHINGTON: Scientists using NASA’s Perseverance rover have gained a clearer picture of the organic carbon detected on Mars as they continue to investigate whether the planet may once have supported life.

New research described the structure of organic carbon identified last year in sedimentary rock that also contained a potential biosignature, or a possible indication of past microbial life. The mudstone is believed to have formed roughly 3.2 billion to 3.8 billion years ago beneath a body of water that no longer exists in Jezero Crater in Mars’ northern hemisphere.

Organic carbon is significant because it is the molecular basis for all known living organisms and underpins molecules involved in DNA, cells and proteins. However, its presence alone is not evidence of life, since it can also be produced through non-biological processes, including chemical interactions between rock and water.

The organic carbon was detected in two rocks in Jezero Crater, named Cheyava Falls and Walhalla Glades. According to planetary scientist Ashley Murphy of the Planetary Science Institute in Arizona, a co-leader of the new research published in Science Advances, the two rocks were sampled at points about 330 feet, or 100 metres, apart.

Last year, researchers announced a potential biosignature in one of the rocks. At that time, NASA also released an image of the Cheyava Falls rock showing a very fine-grained, rusty red mudstone with ring-shaped features resembling leopard spots and dark markings likened to poppy seeds. Such features on Earth can be associated with microbial activity. A potential biosignature is defined as a substance or structure that may have a biological origin but requires additional data and study before any conclusion can be reached.

A closer look at the findings

Using Perseverance’s SHERLOC instrument, the researchers examined the complex form of carbon, known as macromolecular carbon, found in the two rocks. They said the material shares characteristics with carbon formed through biological or non-biological processes on Earth, and also with carbon produced through abiotic processes in meteorites.

This is the first time macromolecular carbon has been identified in mudstones in Jezero Crater, where Perseverance landed in 2021. NASA’s Curiosity rover had previously found macromolecular carbon at Gale Crater, about 2,300 miles, or 3,700 kilometres, away.

Planetary scientist Kyle Uckert of NASA’s Jet Propulsion Laboratory in California, also a co-leader of the study, said the findings point to the possibility that habitable conditions and organic material were once present across Mars on a broad scale.

"These findings indicate that the habitability of Mars and the availability of organic materials may have been widespread across the planet billions of years ago,"

Uckert said the results add to evidence that ancient Mars had the chemical ingredients and environmental conditions that could have supported life, but do not amount to proof of life or resolve whether the carbon had a biological or non-biological origin.

"This strengthens evidence that ancient Mars had chemical ingredients and environmental conditions that could have supported life, but does not provide proof of life, nor ​does it push the needle any further towards ​biotic or abiotic origins,"

He added that the rover’s instruments cannot determine whether the carbon was produced through biological activity that may have involved microbes.

"We need the return of these samples to Earth for more rigorous testing with higher sensitivity and higher resolution laboratory instruments,"

Now cold and barren, Mars is thought to have had a thicker atmosphere and a warmer climate during perhaps the first third of its history, allowing liquid water to exist on its surface. Like Earth and the other planets in the solar system, Mars formed about 4.5 billion years ago.

Water is regarded as a key ingredient for life, which is why Perseverance has been exploring Jezero Crater since 2021. Scientists believe the area was once flooded and contained an ancient lake basin formed after river channels spilled over the crater wall. Such watery environments may have provided habitats for microbes.

"The only place in the universe where we know life has emerged is Earth," Uckert said. “If life is ​discovered on Mars, it could indicate that the emergence of life is not restricted to Earth, assuming the right conditions and ingredients are available, which would be a profound discovery.”