NASA's Perseverance rover has provided new insights into the nature of organic carbon detected on Mars, offering clues about whether the planet ever harbored life. The organic carbon, found in sedimentary rock within Jezero Crater, is the molecular backbone for all known living organisms. However, its presence alone does not confirm past life, as it can also form through non-biological processes.
Discovery of Organic Carbon in Jezero Crater
The organic carbon was detected in two rocks named Cheyava Falls and Walhalla Glades, located about 330 feet (100 meters) apart. These rocks are mudstones that formed between 3.2 and 3.8 billion years ago beneath an ancient lake in Jezero Crater. The discovery was announced last year alongside the identification of a potential biosignature in one of the rocks.
Planetary scientist Ashley Murphy of the Planetary Science Institute in Arizona, co-leader of the new research published in the journal Science Advances, explained that the rocks were sampled by the rover at locations within the crater. The Cheyava Falls rock exhibits ring-shaped features resembling leopard spots and dark marks similar to poppy seeds, which on Earth can be associated with microbial activity.
Analysis of Macromolecular Carbon
Using Perseverance's SHERLOC instrument, researchers examined the complex carbon, known as macromolecular carbon, present in the two rocks. They found that this carbon shares similarities with carbon formed through both biotic and abiotic processes on Earth, as well as abiotic carbon found in meteorites. This marks the first discovery of macromolecular carbon in mudstones within Jezero Crater, where Perseverance landed in 2021.
Previously, NASA's Curiosity rover found macromolecular carbon at Gale Crater, located about 2,300 miles (3,700 km) away. The new findings suggest that organic materials were widespread across ancient Mars.
Implications for Martian Habitability
Planetary scientist Kyle Uckert of NASA's Jet Propulsion Laboratory in California, co-leader of the study, stated: "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." He added, "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."
The rover's instruments cannot determine whether the carbon arose from biological processes. Uckert emphasized, "We need the return of these samples to Earth for more rigorous testing with higher sensitivity and higher resolution laboratory instruments."
Ancient Mars: A Wetter, Warmer World
Mars, now cold and desolate, once had a thicker atmosphere and warmer climate, allowing liquid water on its surface. The planet formed about 4.5 billion years ago, like Earth and other solar system planets. Water, a key ingredient for life, is why Perseverance has been exploring Jezero Crater since 2021. This area was once flooded with water and home to an ancient lake basin, with river channels spilling over the crater wall to create a lake. These water bodies could have been habitats for microbes.
Uckert noted: "The only place in the universe where we know life has emerged is Earth. 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."
