Is there life on Mars?
On March 14, a Russian rocket carrying a new Mars orbiter will (all being well) shoot off on its way to the Red Planet.
The first part of the European Space Agency's ExoMars mission, which is run in cooperation with Russian agency Roscosmos, will launch from the Baikonur cosmodrome in Kazakhstan with the aim of reaching Mars in October. Once in orbit, the Trace Gas Orbiter (TGO) will start trying to sniff out clues to one of space research's enduring questions: Is there life on Mars?
"We know that in the past Mars had conditions on its surface—say 4 billion years ago—that were similar to those on the Earth at the time when life appeared on our planet," ExoMars project scientist Jorge Vago said in a phone call. "So this is a very strong motivation to go to search for signs of life on Mars."
Methane on Mars
The Trace Gas Orbiter follows on from the findings of the Mars Express Orbiter, which was launched by ESA in 2003 and is still active. In 2004, Mars Express detected methane in the Martian atmosphere, which got scientists—and ET fans—very excited. As methane would react in the atmosphere to form water or carbon dioxide, its continued presence means there must be a source replenishing it, and one tantalising option is biological activity.
"On Earth, 90 percent of the methane is the result of bacterial activity—either bacteria living today or microorganisms that lived many hundreds of millions of years ago that died," explained Vago. Organic matter can release methane when it decomposes.
However, methane on Mars could also be explained by geological activity; when certain minerals undergo hydrothermal reactions they give off hydrogen, which reacts with carbon dioxide to form methane (carbon dioxide makes up 95 percent of the Martian atmosphere).
The methane detected by Mars Express was a tiny amount at around ten parts in a thousand million; it's gases in this kind of "trace" concentration that the TGO will focus on. The orbiter will help to confirm the Mars Express findings and explore the origin of the methane. The TGO's spectrometers are a lot more sensitive than those on Mars Express—ESA claims they'll offer three orders of magnitude greater accuracy—which could help settle some of Mars's enduring methane mysteries.
"We're not just looking for the methane; we're looking for a bunch of other gases as well, which in association with the methane may help us to try to determine whether it is biological or geological in origin," said Vago.
"We don't think it is possible for microorganisms to be alive today very close to the surface"
But the scientist warned against getting too excited about greeting some extraterrestrial buddies. "I just want to say that, even in the case of life, we don't think it is possible for microorganisms to be alive today very close to the surface, because the doses of ionising radiation that penetrate through the very thin atmosphere would kill organisms in a short while," he said.
If the methane does have a living origin, it's probably from bacteria living well under the planet's surface.
Teaching Europe to Land
As well as its science mission, the orbiter will also act as a telecoms satellite for rovers on Mars, and especially the ExoMars rover, which is scheduled to launch in 2018 and will be Europe's first. The rover will also be looking for signs of life, though its mission is somewhat separate from the TGO; it will likely be exploring signatures of ancient life. While it is equipped with a drilling instrument, it will only reach samples at a maximum depth of two metres, and we wouldn't expect any life today to be so close to the surface.
Though the ExoMars rover is launching after the orbiter, it won't be able to build directly on the TGO's findings, as Vago explained that the landing site needs to be carefully characterised years in advance. So even if we did get some results pretty sharpish about where methane could be on Mars—and that won't be until 2017 at the earliest—it's unlikely we could target the rover to land in a new area.
The 2016 part of the mission will also see something land on Mars, though nothing quite as exciting as a rover. Schiaparelli is an entry, descent, and landing demonstrator module that will launch with the orbiter. Just before the orbiter reaches Mars's atmosphere, Schiaparelli will be ejected to start its descent to Mars.
The point of Schiaparelli is simply for Europe to test its landing technology. "This is basically something that we hope will teach us Europeans to land on Mars," said Vago.
It will however also have a few scientific sensors to make observations on the surface before its batteries run out. The timing of the landing is also interesting; Schiaparelli is set to make its descent during Mars's "dust storm season" which engineers usually avoid. Schiaparelli will therefore help optimise future landers for these conditions.
A Joint Mission
The ExoMars mission has had a pretty tortuous journey so far—it originally bloomed from a more modest ESA mission to become a joint ESA and NASA endeavour, only for budget constraints to cause NASA to pull out (though some of the instruments still have NASA involvement). Roscosmos agreed to launch the mission using its Proton rocket, and then became a partner in 2013.
Now the 2016 mission is all set and should liftoff on its seven-month journey to Mars on Monday morning, European time. ESA is still shooting for 2018 for the launch of the ExoMars rover, though there are rumours that it could face delays and Vago conceded that the schedule to build the flight model is tight.
Ultimately, he thinks ExoMars could be one of ESA's most important missions. Asked what his ideal outcome for the 2016 orbiter mission would be, he responded: "The best and most detailed characterisation ever of Mars's atmosphere and, hopefully, something—how should I put it?—something that is not wishy-washy about the possible origin of the methane."