In a few days, space engineers will launch a probe that is designed to sniff out life on Mars.
The ExoMars robot spacecraft – which will blast off from the Baikonur cosmodrome in Kazakhstan on 14 March – will use a highly sensitive detector to determine whether methane, which is produced by living beings on Earth, exists in significant levels high in the atmosphere or near the surface of Mars.
The mission is designed to pinpoint hotspots that have high methane levels and that may provide the best prospects of finding life in the area. These would be targeted for future Mars missions.
“Essentially our spacecraft is a giant nose in the sky,” said Jorge Vago, the ExoMars project scientist. “And we are going to use it to sniff out the presence of methane on Mars and determine if it is being produced by biological processes.”
Most of the methane in Earth’s atmosphere is produced by micro-organisms, including many species that thrive in the guts of animals including cattle and termites. The gas’s presence in the atmosphere of Mars would provide strong support for the idea that life forms of some kind exist – or existed in the past.
To create a methane map of Mars, European Space Agency scientists have collaborated with Russian counterparts and designed ExoMars, a double mission whose first part will be launched in a few days and will put a probe, called the Trace Gas Orbiter, into orbit around the red planet. This will test for Martian methane. The probe will also test a package of landing equipment that could be used in the second part of the mission, a robot rover to be launched in 2018.
The Trace Gas Orbiter uses a suite of highly sensitive spectrometers, which can pinpoint the presence of the gas at extremely low levels. “Whiffs of methane have been detected by previous missions to Mars,” said Vago. “However, our detectors should be able to detect it at levels of only a few parts per trillion.”
The orbiter will use two approaches in its methane search. The first will involve viewing the planet at dawn and dusk, when the Sun will shine straight into the probe’s detectors. “This will give us detailed information about amounts of methane at different heights above the Martian surface,” said the Open University’s Manish Patel, who has designed some of the orbiter’s gas detectors. “The second part of our search will involve peering straight down on to the surface. In that way we will be able to map the planet’s methane hotspots.”
The orbiter’s spectrometers will be able to detect chemicals other than methane, however. They will also pinpoint other gases that will be vital in proving whether Martian methane has been produced by living entities or is merely the by-product of geological processes. “Some of the methane in our own atmosphere has come from geological processes, so we have to eliminate those as possible sources of the methane that we find on Mars,” said Patel. “That is a crucial part of our research.”
This point is emphasised by Vago. “If methane is found in the presence of other complex hydrocarbon gases, such as propane or ethane, that will be a strong indication that biological processes are involved. However, if we find methane in the presence of gases such as sulphur dioxide, a chemical strongly associated with volcanic activity on Earth, that will be a pretty sure sign that we are dealing with methane that has come from the ground and is a by-product of geological processes.”
The mission will also release a small landing craft called Schiaparelli, named after the Italian astronomer who, in the late 19th century, drew some of the first maps of Mars. The lander will beam back precise information about its behaviour as it descends through the atmosphere.
“Mars is one of the most difficult worlds in the solar system to land on and Europe has very little experience in settling probes safely on its surface,” said Stephen Lewis of the Open University, who has also been involved in the design of the spacecraft. “The information from Schiaparelli could be crucial in telling us what to expect when it comes to landing the second part of the mission – the robot rover – on the planet in two years.”
