NASA’s Curiosity rover has identified a wide range of organic molecules on Mars, including compounds that scientists consider key ingredients for the origin of life on Earth.
The discovery comes from a chemical experiment carried out on another planet for the first time. Results show that the Martian surface is capable of preserving molecules that could act as potential signs of ancient life. However, the experiment cannot determine whether these organic compounds came from past life on Mars, natural geological processes, or meteorites that struck the planet.
To confirm any true evidence of past life, scientists would need to bring Martian rock samples back to Earth for detailed study.
New Experiment Reveals Preserved Ancient Chemistry
The research was led by Amy Williams, Ph.D., a geological sciences professor at the University of Florida and a member of both the Curiosity and Perseverance rover science teams. Curiosity arrived on Mars in 2012 to investigate whether the planet once had conditions suitable for microbial life. Perseverance, which landed in 2021, is focused on searching for direct signs of ancient life.
“We think we’re looking at organic matter that’s been preserved on Mars for 3.5 billion years,” said Williams, who helped develop the experiment. “It’s really useful to have evidence that ancient organic matter is preserved, because that is a way to assess the habitability of an environment. And if we want to search for evidence of life in the form of preserved organic carbon, this demonstrates it’s possible.”
Williams and an international team published the findings April 21 in the journal Nature Communications.
DNA-Like Molecule Among Key Discoveries
The experiment identified more than 20 different chemicals. Among them was a nitrogen-containing molecule with a structure similar to compounds involved in building DNA, something never before detected on Mars. The rover also found benzothiophene, a large sulfur-containing molecule with two connected rings, which is commonly delivered to planets by meteorites.
“The same stuff that rained down on Mars from meteorites is what rained down on Earth, and it probably provided the building blocks for life as we know it on our planet,” Williams said.
Gale Crater and Clay Minerals Preserve Organics
Curiosity, operated by NASA’s Jet Propulsion Laboratory, landed in Gale crater in August 2012. This site was once a lake bed. The experiment took place in 2020 in the Glen Torridon region, an area rich in clay minerals that formed in the presence of water. These clays are especially good at trapping and preserving organic material, making them ideal locations for this type of investigation.
SAM Instrument and TMAH Chemical Analysis
The analysis was carried out using the Sample Analysis at Mars instrument suite, known as SAM. Jennifer Eigenbrode, Ph.D., an astrobiologist at NASA’s Goddard Space Flight Center and co-author of the study, helps lead the instrument team. SAM has contributed many of the mission’s key discoveries about Mars’ chemistry, atmosphere, and potential habitability.
In this experiment, scientists used a chemical called TMAH to break down larger organic molecules into smaller fragments. These fragments could then be examined by SAM’s onboard instruments. Because Curiosity only carries about two cups of TMAH, researchers had to carefully plan the experiment and select the best possible sampling site.
Implications for Future Mars and Titan Missions
The success of this method is shaping future exploration plans. Upcoming missions, including the Rosalind Franklin rover on Mars and the Dragonfly mission to Saturn’s moon Titan, are expected to carry similar TMAH-based experiments to search for organic compounds.
“We now know that there are big complex organics preserved in the shallow subsurface of Mars, and that holds a lot of promise for preserving large complex organics that might be diagnostic of life,” Williams said.
