Billions of years ago, Mars looked quite different from the cold, arid planet we see today. Scientists believe that in the distant past, the Red Planet had a warmer climate, flowing liquid water, and a thicker atmosphere. These conditions could have supported simple forms of life. But the big question remains: did life ever actually exist on Mars?
NASA’s rovers have already found organic molecules in Martian rocks. These molecules contain carbon and are fundamental building blocks of life on Earth. However, they can also form through purely chemical, nonliving processes, making it difficult to determine if these molecules are evidence of ancient life.
Now, scientists are gearing up for a new phase in this quest. The European Space Agency’s Rosalind Franklin rover, set to land on Mars in 2030, aims to search for organic compounds that might indicate past life. Recently, researchers from Germany and France tested one of the rover’s key scientific tools. Their results suggest that the rover could detect a specific kind of molecular clue known as chirality.
Some organic molecules exist in two mirror-image forms, similar to how your left and right hands are mirror images. These are called enantiomers. Even though they contain the same atoms, their 3D arrangements differ. This property could help scientists distinguish molecules related to life from those formed by nonbiological means. On Earth, organisms usually use only one of the two mirror-image forms because life tends to pass on specific molecular patterns. In contrast, nonliving chemical reactions generally produce equal amounts of both mirror images.
The researchers focused on two hydrocarbons, pristane and phytane, which come from living organisms on Earth and are found in petroleum. These compounds are very stable, meaning they could potentially survive billions of years on Mars. The Rosalind Franklin rover carries an instrument called the Mars Organic Molecule Analyzer (MOMA), which uses heating, gas chromatography, and mass spectrometry to identify organic molecules and determine their chirality.
To test MOMA’s capabilities, scientists analyzed samples from the Murchison meteorite, which fell in Australia in 1969. The meteorite contains a rich variety of organic compounds and acts as a good stand-in for Martian material. The team expected to find signs of Earth-based contamination, but instead, they discovered equal amounts of both mirror-image forms of pristane and phytane. This indicated that the molecules likely did not originate from living organisms.
The scientists suggest that these compounds might have entered the meteorite during its passage through Earth’s atmosphere, possibly through contact with tiny particles released by fossil fuel combustion. Over time, heat and pressure inside petroleum-rich rocks can erase the molecular imbalance typical of biological origin, resulting in equal amounts of both mirror images.
This study demonstrates that the Rosalind Franklin rover’s instrument can effectively differentiate between mirror-image molecules. More importantly, it offers a promising new tool in the search for ancient life on Mars and prompts fresh questions about how organic molecules traverse space and reach Earth.