Trace Gas Orbiter spots unexpected gases in Martian atmosphere

A European Space Agency instrument in orbit around Mars has spotted unexpected gases in the planet’s atmosphere, which could help to explain a longstanding mystery regarding the presence of methane there.

The ExoMars Trace Gas Orbiter (TGO) recently completed a full Martian year of observations (approximately two Earth years) and has found signatures of both ozone (O3) and carbon dioxide (CO2) for the first time. The Martian atmosphere is composed predominantly of carbon dioxide which makes up 95% of the atmosphere, with less than 0.2% of oxygen. But in the particular wavelength the TGO investigates, the scientists were expecting to see methane, not carbon dioxide or ozone.

“These features are both puzzling and surprising,” lead author Kevin Olsen of the University of Oxford said in a statement. “They lie over the exact wavelength range where we expected to see the strongest signs of methane. Before this discovery, the CO2 feature was completely unknown, and this is the first time ozone on Mars has been identified in this part of the infrared wavelength range.”

 Artist’s impression of the ExoMars 2016 Trace Gas Orbiter at Mars.
Artist’s impression of the ExoMars 2016 Trace Gas Orbiter at Mars. ESA/ATG medialab

Carbon dioxide and ozone have been previously observed by instruments like Mars Express, but the TGO was able to see these gases in the infrared wavelength for the first time, allowing scientists to see deeper into the Martian atmosphere and find traces of the gases at lower altitudes than was possible before.

The TGO is searching for methane signatures to unravel a longstanding mystery about Mars: Why does methane appear in small amounts in the Martian atmosphere when measured by some instruments, but not when measured by others? This question is particularly important because methane is a gas associated with life: It can be given off by living organisms, but it can also be created by geological processes. Now, this latest data could help to explain discrepancies in previous findings.

“Discovering an unforeseen CO2 signature where we hunt for methane is significant,” said fellow lead author Alexander Trokhimovskiy of the Space Research Institute of the Russian Academy of Sciences in Moscow in the statement. “This signature could not be accounted for before, and may therefore have played a role in detections of small amounts of methane at Mars.”

And this new information adds to our overall understanding of the complex Martian atmosphere. “Ozone and CO2 are important in Mars’ atmosphere,” Trokhimovskiy said. “By not accounting for these gases properly, we run the risk of mischaracterising the phenomena or properties we see.”

The findings are published in two articles in the journal Astronomy & Astrophysics.

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