Mission Type: Lander, Orbiter
NASA Center: Jet Propulsion Laboratory
References:
ExoMars/Trace Gas Orbiter mission profile, http://mars.jpl.nasa.gov/programmissions/missions/future/exomarstgo/

The ExoMars/Trace Gas Orbiter mission is a joint mission being developed by the European Space Agency (ESA) and NASA/JPL. This mission would be the first in a series of joint missions to Mars for ESA and NASA. The two space agencies signed the Mars Exploration Joint Initiative agreement in 2009.

Led by ESA, a new spacecraft carrying a demonstration lander would arrive at Mars in 2016. The lander is designed to demonstrate the European capability of entry, descent, and landing at Mars. The orbiter would conduct an exhaustive survey of trace gases in the Mars atmosphere, in order to understand their atmospheric lifetimes and the location and nature of subsurface sources that produce gases, such as methane.

NASA would supply the launch vehicle, four science instruments, and a communications system. ESA would build the orbiter and supply one orbiter science instrument package and the lander. The lander would be released from the orbiter a few days prior to the Mars Orbit Insertion (MOI). The orbiter would spend several months aerobraking through Mars' atmosphere. During aerobraking, the spacecraft uses friction from the Martian atmosphere to slow down. This helps the orbiter settle into a circular orbit around Mars.

Is Mars still alive? Scans of the Martian atmosphere show methane gas plumes in different locations at different times. Since methane is short-lived on geological time scales, its presence implies the existence of an active, current source of methane. The nature of that source -- biological or chemical -- is not clear. Organisms on Earth release methane as they digest nutrients. However, other purely geological processes, such as oxidation of iron, also release methane. Although there is no evidence on Mars of active volcanoes today, ancient methane trapped in ice "cages" called clathrates might now be released. In any case, Mars is "active" today.

The orbiter would map the variable distributions of trace gases in Mars' atmosphere, including methane and its isotopes. Detection of other gases (e.g., sulfur dioxide) would provide clues as to whether their release is volcanic, tectonic or biological in nature. Different gases may have different sources. Once pinpointed, the places where these gas sources are found could be prime landing sites for future missions. In any case the 2016 orbiter would serve as a telecommunications satellite for a joint ESA/NASA mission that would launch in 2018 and land two new rovers on Mars.