Earlier today, March 14, at Baikonur Cosmodrome in Kazakhstan, the first phase of the ExoMars mission launched atop a Russian Proton rocket. Its destination is the red planet, and its mission is to find "biosignatures," or scientific markers of life. As of press time, the launch was proceeding as planned, according to the European Space Agency (ESA).

ExoMars is short for "exobiology on Mars," and is a joint collaboration between the ESA and Roscosmos, the Russian Space Agency. Today's launch included a satellite called the Trace Gas Orbiter. As its name suggests, the orbiter is designed to study trace gases, which make up less than 1 percent of the Martian atmosphere. One such gas, methane, is vital to understanding life on Mars. Because the gas survives only a matter of centuries before breaking down, any methane registered will have to have been produced relatively recently by active volcanoes or microorganisms. Either source would be exciting, and planetary scientists will use other trace gases in the atmosphere to determine the origin. Sulfur dioxide in the air would suggest volcanism; carbon-12 would suggest life.


This phase of the ExoMars mission will also launch a prototype "entry, descent, and landing" module named Schiaparelli. (It's named after the 19th-century Italian astronomer Giovanni Schiaparelli, who mapped Mars based on his telescopic observations. Features he labeled "channels" in Italian were mistranslated into English as "canals." American astronomer Percival Lowell ran with the notion, creating his own maps of a Mars covered with imaginary waterways—and thus the notorious "canals of Mars" were born.)

Schiaparelli is designed to test technologies for setting payloads gently on Mars. As it approaches the surface in October, it will orient itself and engage its parachute systems and landing engines. Meanwhile, an onboard instrument array called AMELIA (Atmospheric Mars Entry and Landing Investigation and Analysis) will measure wind speeds and atmospheric variables during the descent. Because the landing will take place during Mars's dust storm season, one of the instruments will look into the role of electric forces on dust lifting, the mechanism that initiates dust storms. The information gathered will be invaluable for future missions, including the second phase of ExoMars, which launches in 2018 and will set a rover on the Martian surface in 2019.

The Trace Gas Orbiter will circle Mars at an altitude of 400 kilometers and carries four scientific instruments. The Atmospheric Chemistry Suite (ACS) and the Nadir and Occultation for Mars Discovery (NOMAD) will scan for trace gases. The Colour and Stereo Surface Imaging System (CASSIS) will study areas identified as possible trace gas sources, and help scientists determine what geologic processes are at work there. The Fine Resolution Epithermal Neutron Detector (FREND) can map the hydrogen content of regions of the Martian surface, going one or two meters deep.

The Schiaparelli lander, meanwhile, has enough battery life for two to eight Martian days. (Export controls prevented ESA designers from using a Russian-made radioisotope thermoelectric generator, which could have provided years of power.) In addition to gathering data during the descent, once the module is safely on the ground, it will analyze electric fields on the Martian surface—a first for any mission—and study atmospheric transparency, humidity, wind speed, and wind direction.


Before ExoMars was a joint ESA-Roscosmos mission, it was a joint ESA-NASA mission. In 2012, however, NASA withdrew, its planetary science budget having been slashed. (A year earlier, facing a starvation budget, NASA was also forced to withdraw from a different joint mission with ESA to the Jovian system. On that mission, NASA was to explore Europa while ESA went to Ganymede.) The loss of NASA was a blow to ExoMars and a big problem for ESA, which had already invested hundreds of millions of euros in technology development and was counting on NASA to provide a launch vehicle, communications package, instrumentation, and eventually, a lander for the rover. (Ultimately, NASA contributed only the communications system.) Roscosmos saved the day with its rockets, instruments, and for the next phase, a lander.

Neither agency—ESA or Roscosmos—has a perfect track record of missions to Mars. (NASA's Mars record is likewise marked with crashes and disappearances. "Mars is hard," as Jet Propulsion Laboratory engineers are known to say. With respect to landings, Mars has just enough atmosphere that it has to be dealt with, but not enough that it can be much help.) Russia's last two Mars missions—Fobos-Grunt in 2011 and Mars 96 in 1996—never escaped low Earth orbit. ESA's Beagle-2 lander disappeared before making contact with the surface in 2003. It was declared lost, though NASA's Mars Reconnaissance Orbiter found it last year. As it turns out, Beagle-2 landed successfully, though part of its solar panel array failed to deploy, obstructing its communications package.

A successful ExoMars mission will entail the spacecraft arriving at Mars in October, at which time the Trace Gas Orbiter and lander will separate. On October 19, the satellite will be placed into Martian orbit and Schiaparelli will begin its entry, descent, and landing. The Trace Gas Orbiter will then spend just over one year "aerobraking," in which it is gently lowered to its science-ready orbital altitude of 400 kilometers. The science mission begins in December 2017.

The Trace Gas Orbiter will be the second spacecraft ESA has placed into orbit around Mars. The first was Mars Express on Christmas Day 2003—the same mission in which Beagle-2 was lost. Mars Express remains in Martian orbit and is currently studying the planet's surface and subsurface.