"These features are both puzzling and surprising..."
The TGO (Trace Gas Orbiter) orbiter of ESA’s ExoMars mission has detected never-before-seen signatures of ozone (O3) and carbon dioxide (CO2) while orbiting Mars.
The TGO has spent two years seeking to understand the mixture of gases that make up the Martian atmosphere, and more specifically, the mystery surrounding the presence of methane on the planet.
According to a recent statement by the European Space Agency, the spacecraft has stumbled across never-before-seen signatures of ozone (O3) and carbon dioxide (CO2)– based on a full martian year of observations by its sensitive Atmospheric Chemistry Suite (ACS).
The findings are described in two articles published in “Astronomy & Astrophysics,” one led by Kevin Olsen of the University of Oxford (UK) and the other by Alexander Trokhimovskiy of the Space Research Institute of the Russian Academy of Sciences in Moscow.
“These features are both puzzling and surprising,” explained Olsen.
“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.”
The Martian atmosphere is dominated by 95% carbon dioxide, 3% nitrogen, 1.6% argon, and it has traces of oxygen, carbon monoxide, water, methane, and other gases, along with a lot of dust. Scientists observe the atmosphere to measure temperatures, track seasons, explore air circulation, and much more.
Ozone – which forms a layer in the upper atmosphere of both Mars and Earth – helps keep atmospheric chemistry stable.
Spacecrafts, like ESA’s Mars Express probe, have detected CO2 and ozone. Still, ACS’s outstanding sensitivity aboard the TGO has made it possible to reveal new details about how these gases interact with light.
Observing ozone in the range where the TGO searches for methane is a result that no one anticipated.
Although scientists have already mapped variations in Martian ozone as a function of altitude, until now, they have used methods that rely on gas footprints in the ultraviolet, a technique that only allows measurements to be made at high altitudes (more than 20 kilometers per above the surface).
The new results demonstrate that it is also possible to map Martian ozone in the infrared, so its behavior can be measured at lower altitudes to get a more detailed view of its role in the planet’s climate.
All of this contributes to our better understanding of Mars’ mysterious methane because one of the main objectives of the TGO is to explore the Martian methane.
To date, Martian methane signals – first spotted by missions like ESA’s Mars Express in orbit and NASA’s Curiosity rover on the surface – are variable and puzzling.
Although methane can be generated through geological processes, most of the methane on Earth is produced by living organisms, from bacteria to livestock and human activities.
For this reason, it is exciting to detect methane on other planets, especially since it is known that this gas decomposes after about 400 years, which implies that all the methane present must have been generated or released in the relatively recent past.
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