The Rosalind Franklin rover, part of the joint European-Russian ExoMars program, will carry an instrument capable of testing the chirality of organic molecules on Mars—a potential biological signature. While previous rovers have detected organic compounds, those molecules could arise from non-biological processes. Chirality, or handedness, is a geometric property: life on Earth overwhelmingly produces molecules of one handedness, making its measurement a more robust biosignature.
The instrument, whose successful test was confirmed in a recent study, examines whether Martian organic molecules show an excess of one chiral form. Such an imbalance would strongly suggest biological origin, whereas a racemic mixture—equal parts left- and right-handed—would point to abiotic chemistry. The test validates the instrument's ability to survive launch and the harsh Martian environment.
The rover is now slated for launch in the 2030s, delayed from its original 2020 window due to technical issues and the geopolitical fallout from Russia's invasion of Ukraine. Its mission is to drill up to two meters into the Martian subsurface, where organics may be protected from surface radiation.
If chirality is detected, it would be the strongest evidence yet for past or present life on Mars. The find would reshape planetary science and astrobiology, supporting the hypothesis that life—at least microbial—can emerge on rocky worlds beyond Earth.
A key caveat: even a chiral signal could have non-biological origins—certain mineral surfaces and ultraviolet light can also bias handedness. The rover's data will need to be cross-referenced with other geochemical and mineralogical measurements to rule out abiotic processes.