A New Eye in the Sky Will Help Search for Life on Mars

A partnership between European and Russian space agencies called ExoMars has put a new instrument into orbit around the Red Planet that will look for signs of methane.

ExoMars Trace Gas Orbiter at Mars, which will search for evidence of methane and other atmospheric gases that could be signatures of active biological or geological processes on Mars. | European Space Agency
ExoMars Trace Gas Orbiter at Mars, which will search for evidence of methane and other atmospheric gases that could be signatures of active biological or geological processes on Mars. | European Space Agency

The search for life on Mars will soon have another set of eyes in orbit, helping to find evidence of habitability. The Trace Gas Orbiter (TGO) — part of the European-Russian ExoMars mission — is just about to settle into its lower, operational orbit. When it's ready, a Russian instrument will search for signs of methane in the atmosphere.

Mars may have been habitable in the ancient past. The surface is dry today, but the planet used to have running water on its surface. We can see ancient gullies from orbit, and several rovers, such as NASA's Curiosity rover, found evidence of rocks that formed in water on the surface. A feature called recurring slope lineae produces dark streaks on the slopes of Martian craters during warmer parts of the year, but it's unclear if this is actually from briny water. Some research suggests the hydrated salts seen in RSLs come from atmospheric water, or that RSLs are only features that arise from tumbling, dry sand.

Scientists want to thoroughly investigate the Red Planet before jumping to conclusions about its habitability. Future Mars rovers will probe for habitable environments and in some cases, such as NASA's Mars 2020, will cache the most promising samples for a potential mission that would bring the samples back to Earth. Other missions examine the Martian atmosphere, and TGO will play a key part in that research because its search for methane.

An illustration shows the main photochemical pathways known or expected to occur on Mars and their relation to ACS measurement capabilities. | MIPT Press Office

Methane can be produced by biological processes or by non-biological processes, such as volcanism. The gas has been very hard to measure in the Martian atmosphere. Curiosity saw a spike in methane levels near its landing area of Gale Crater in 2013 and 2014 during the planet’s autumn. But when autumn rolled around in 2016, the methane spike didn't repeat itself.

While other instruments on Earth have tried to measure methane levels on Mars, the measurements have been inconsistent — presumably because the great distance between the planets makes methane hard to see. So, one of the valuable contributions of TGO will be accurate measurements of methane from up close.

"It enables measurements of the Martian atmosphere that are hundreds of times more accurate than ever before," chief engineer Alexander Trokhimovskiy of Russia's Space Research Institute said in a press statement from the Moscow Institute of Physics and Technology (MIPT).

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ExoMars is a partnership between the European Space Agency and Roscosmos, Russia’s space agency. Russia has two instruments on board the spacecraft, including the Atmospheric Chemistry Suite, which can detect many types of trace atmospheric gases, including methane. ACS includes three spectrometers that can point straight down or across the Martian atmosphere, looking at key molecules for habitability.

With this information in hand, scientists can refine their models of the Martian atmosphere. "MIPT has developed data-processing algorithms and designed a general circulation model of Martian atmosphere, which is required for planning experiments and interpreting their results," Alexander Rodin, the head of institute's applied infrared spectroscopy lab, said in the release.

ExoMars will have two major spacecraft to it. TGO successfully launched in 2016 and arrived at Mars safely, although it lost a small demonstrator lander called Schiaparelli. European and Russian representatives are now developing the ExoMars rover. The rover was originally expected to launch in 2018, but developmental delays pushed the launch back date to 2020. A landing site for the rover should be announced later this year.

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