2016 Trace Gas Orbiter Mission

2016 ExoMars Trace Gas Orbiter
Shown here is an artist’s rendition of the ExoMars Trace Gas Orbiter spacecraft, which includes the descent module that will test surface landing capabilities. (Courtesy European Space Agency)

The Mars mission that will follow MAVEN is the ExoMars Trace Gas Orbiter (EXMTGO) to be launched in 2016. This will be a joint mission between NASA and ESA, with NASA providing the launch vehicle and four of the science instruments, and ESA providing the spacecraft and one of the instruments. After a joint proposal and evaluation process, the selection of the science instruments for the mission was recently announced.

The focus of the science will be on detecting and characterizing trace gases in the Martian atmosphere. Gases such as methane, which has been detected previously in the Martian atmosphere, could result from either ongoing geological or biological processes. By looking for a lot of different gases in the atmosphere, it will be possible to determine what processes are active today and whether there is active geology or biology. The instruments that were selected will look for trace gases in the atmosphere, map them out over a Mars year, and provide details on the “weather context” of the atmosphere that are necessary to understand them.

MAVEN and EXMTGO both stand on their own, each one able to achieve its own science objectives. But there will be tremendous value in combining measurements made by each, even though they will be made in different years. EXMTGO arrives about two Earth years, or one Mars year, after MAVEN. Among the gases that EXMTGO will look at in the lower atmosphere are those that are produced by photochemical processes (for example, looking at CO and O that is produced by the breakup of CO2 by sunlight). These processes provide the sources for many of the gases that MAVEN will observe in the upper atmosphere, including some that are escaping. The combination of MAVEN and EXMTGO measurements will provide detailed information on photochemical processes from the bottom of the atmosphere to the top, and on coupling between the lower and the upper parts of the atmosphere.

We’ve ended up with two first-rate atmospheric missions to Mars. Along with the geologically focused missions, the overarching theme is that we are trying to understand the long-term history of Mars and what the potential has been for life to exist there. The Mars environment is a complex system of coupled processes, so that understanding it in detail requires understanding each component separately as well as how they interact. In hindsight, it is easy to see how the missions of the last two decades have provided much of the information that we need, and how results from both MAVEN and the ExoMars Trace Gas Orbiter will fit into this broader picture.