Billions of years ago, Mars looked very different from the cold, dry world we see today. Scientists believe the Red Planet once had a warmer climate, liquid water and a thicker atmosphere.
These conditions may have been suitable for simple forms of life. But did life ever actually exist on Mars?
That remains one of the biggest unanswered questions in planetary science.
NASA’s rovers have already discovered organic molecules in Martian rocks. Organic molecules contain carbon and are essential building blocks of life on Earth.
However, they can also form through nonliving chemical processes, making it difficult to determine whether any of the molecules found on Mars are signs of ancient life.
Scientists are now preparing for a new chapter in the search. The European Space Agency’s Rosalind Franklin rover, scheduled to arrive on Mars in 2030, is designed to search for organic compounds that could point to past life.
Researchers from Germany and France recently tested one of the rover’s key scientific methods. Their findings suggest that the rover could detect a special type of molecular clue known as chirality.
Some organic molecules exist in two mirror-image forms, much like a person’s left and right hands. These mirror forms are called enantiomers. Although they contain the same atoms, their three-dimensional arrangements are different.
This feature may help scientists distinguish life-related molecules from those produced without biology. On Earth, living organisms almost always use only one of the two mirror forms of a molecule. This happens because life reproduces itself and passes on specific molecular patterns. In contrast, nonliving chemical reactions usually produce both mirror forms in equal amounts.
Researchers focused on two hydrocarbons called pristane and phytane. These molecules originate from living organisms on Earth and are found in petroleum. They are also highly stable, meaning they could potentially survive for billions of years on Mars.
The Rosalind Franklin rover carries an instrument called the Mars Organic Molecule Analyzer, or MOMA. The device uses furnaces, a gas chromatograph and a mass spectrometer to identify organic molecules and determine their chirality.
To test the instrument, the researchers used samples from the Murchison meteorite, which fell in Australia in 1969. The meteorite contains a wide variety of organic compounds and serves as a useful stand-in for Martian material.
The scientists expected the meteorite’s pristane and phytane molecules to show signs of biological contamination from Earth. Instead, they found equal amounts of both mirror forms. This pattern suggested that the molecules probably did not come directly from living organisms.
The researchers believe the compounds may have entered the meteorite during its fall through Earth’s atmosphere, possibly through contact with tiny particles released by fossil fuel burning. Over millions of years, heat and pressure inside petroleum-rich rocks can erase the molecular imbalance associated with life, producing equal amounts of both mirror forms.
The new study demonstrates that the Rosalind Franklin rover’s instrument can successfully distinguish between mirror-image molecules.
More importantly, it provides scientists with a promising new tool in the search for ancient Martian life and raises new questions about how organic molecules move through space and Earth’s atmosphere.
