Europe's ExoMars spots something weird in Mars' atmosphere

The European Space Agency's ExoMars Trace Gas Orbiter (TGO) has found that Mars' atmosphere forms carbon monoxide containing less heavy carbon than expected. The findings help clarify a puzzling discovery made by NASA's Curiosity rover last year.

The discovery aligns with the notion that the presence of carbon-based compounds, known as 'organic matter,' on the Martian surface is likely the result of a combination of sunlight and intricate chemical processes, rather than being indicative of life. 

The team analysed data gathered across eight TGO orbits in March-April 2022 by the European-led NOMAD (Nadir and Occultation for MArs Discovery) instrument.

"Measuring the carbon isotopic ratio in carbon monoxide is a powerful way to understand where the planet's organic matter came from and reveal Mars' history of habitability," says Shohei Aoki of the University of Tokyo and Royal Belgian Institute for Space Aeronomy, and lead author of a new paper published in the Planetary Science Journal.

The atmosphere of Mars consists of two isotopes of carbon: the predominant carbon-12, which constitutes the majority of carbon in the Solar System, and the heavier carbon-13, which is carbon-12 with an additional neutron. By measuring the relative abundance of these isotopes, scientists can gain valuable insights into the history and current state of the Martian environment

At Gale Crater, the landing site of NASA's Curiosity rover, numerous deposits dating back 3.5 billion years were found to have unexpectedly low levels of heavy carbon. Researchers have put forth several potential explanations for this phenomenon, including intermittent deposition of interstellar dust clouds on Mars and the possibility of ancient microbes emitting methane. On Earth, the reduction of heavy carbon is often associated with biological activity, as various biological processes tend to favor the use of lighter carbon isotopes.

"Any phenomenon at Mars that could be caused by life is a cause for excitement, but our findings point in a different direction," says co-author Yuichiro Ueno of Tokyo Tech. University. Instead, we see that the cause for the heavy carbon depletion seen in both Mars’ atmospheric carbon monoxide and in Gale Crater could be chemical.

New science alert! I’ve spotted something weird in Mars' atmosphere! 🔴🛰️🔍Turns out that #Mars' carbon monoxide is ‘lighter’ than it should be. But why? Could biology be to blame… or is it all a matter of chemistry? 🤔 ☀️👉 https://t.co/j4wSOppCDY #ExploreFarther [1/2] pic.twitter.com/RAViNgubyF

— ExoMars orbiter (@ESA_TGO) May 31, 2023