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The ExoMars Trace Gas Orbiter will blast off on Monday on a mission to study the planet’s atmosphere for signs of gases. (ESA/ATG medialab)
The ExoMars Trace Gas Orbiter will blast off on Monday on a mission to study the planet’s atmosphere for signs of gases. (ESA/ATG medialab)

If there’s life on Mars, it must be passing gas Add to ...

Mars, don’t hold your breath … please.

That, in so many words, is the message that scientists will be projecting to the red planet next week when they launch a probe to investigate whether Mars is exhaling puffs of methane gas that could be the biological exhaust fumes of a microbial ecosystem living far beneath the surface.

Dubbed the ExoMars Trace Gas Orbiter, the unmanned spacecraft is part of a European-Russian-led project aimed at finding evidence that Mars can support life. And while some experts remain skeptical that such evidence is there to be found, no one doubts that the scientific implications of a positive detection would be enormous.

“If there is life on Mars, we have probably the best chance so far compared to any other mission to actually find that out,” said project scientist Hakan Svedhem, speaking from the Baikonur Cosmodrome in Kazakhstan, where the probe is set to begin its seven-month journey to Mars on Monday at 5:31 a.m. EDT.

The international mission involves dozens of scientists, including a small contingent from Canada. Collectively, their main objective is to measure the constituents of the Martian atmosphere more precisely than ever before in order to settle a long-running debate about whether there is an active source of methane gas somewhere on the planet.

The question is relevant to the search for life because most of the methane in Earth’s atmosphere is produced by living organisms, from bacteria to cows. Reports of methane on Mars date back more than 40 years, but they have never been conclusive.

Part of the challenge is that Mars has no ozone layer to block out harsh ultraviolet rays from the sun. The rays can break down methane quickly, so any appearance of methane seeping from an underground Martian reservoir likely would be fleeting.

When NASA’s Curiosity rover landed on Mars in 2012, it came with a device capable of sniffing out trace amounts of methane. Initially, it found none, but then in 2013, it detected a sudden spike in its methane readings. Scientists are still debating what Curiosity really saw. Some skeptics speculate that the rover may have gotten a whiff of one of its own components releasing the gas.

The Trace Gas Orbiter will not sample the Martian air directly but rather will look through the planet’s thin atmosphere toward the distant sun. Any trace gases that are present in the atmosphere, including methane, will preferentially absorb sunlight at certain specific wavelengths. The gases give themselves away when those wavelengths don’t show up in the detector.

“Think of it as looking toward the sunrise,” said Ed Cloutis, a planetary scientist at the University of Winnipeg and a member of the mission’s science team. “We’ll be measuring the composition of the gas by the way it affects the sunlight coming through it.”

As the probe orbits Mars, it will repeatedly measure the planet’s atmosphere along different lines of sight toward the sun. Over time, this will allow the spacecraft to see whether methane is associated with any particular features on the surface, and whether methane concentration changes with the seasons.

A clear detection of methane would be a major discovery and would lead to many more questions – the primary one being whether the methane is biological in origin. Although the surface of Mars appears barren and lifeless today, it’s thought to have been a far more hospitable world in the distant past when, at times, water flowed freely over its surface. Scientists wonder whether microbial life could have emerged then, as it did on Earth. If so, some form of Martian life might still persist deep below the surface.

The Trace Gas Orbiter can pick up methane and related chemicals in concentrations as low as fractions of one part per billion. That should allow it to determine whether any methane it sees is the product of a biological or a purely mineral reaction.

But even the latter case would be exciting, Dr. Cloutis said, because it would suggest there is a warm, wet environment below the surface where such mineral reactions can take place and where bacteria might flourish.

Of course, it’s possible the Trace Gas Orbiter may see no sign of methane at all.

“That would be an important result, too,” said Dr. Svedhem, because it would lay the methane question to rest with a high degree of certainty. It would also likely stimulate researchers who are searching for signs of life in the solar system to look elsewhere and in different ways.

Regardless of whether if finds methane, the Trace Gas Orbiter is expected to contribute to scientists’ understanding of the red planet.

“It gets at aspects of the atmosphere that have not yet been explored but that can contribute substantially to our picture of the overall evolution of Mars,” said Bruce Jakosky, principal investigator with NASA’s MAVEN mission, which has been orbiting Mars since 2014 and shedding light on how the planet lost its water over billions of years.

The Trace Gas Orbiter is also carrying a small lander named Schiaparelli that will test the European Space Agency’s ability to successfully conduct a controlled descent to the Martian surface. If successful, the same system will be used for a more ambitious rover mission currently scheduled for launch in 2018.

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