The scientific instruments have been selected for the first U.S.-European joint mission to Mars, and they're going to be looking for methane. The ExoMars Trace Gas Orbiter will be loaded up with gadgets designed to sniff out whether the gas is being generated by geological or biological processes.

Unexpected levels of methane were detected by the European Space Agency's Mars Express orbiter in 2003, and the find was confirmed by ground-based observations supported by NASA and the National Science Foundation. One of the places where plumes of methane are rising into the Martian atmosphere is Nili Fossae, which is considered a prime target in the search for traces of Martian life.

The ExoMars experiments will track down more precisely where Mars' methane is coming from.

"Mapping methane allows us to investigate further that most important of questions: Is Mars a living planet, and if not, can or will it become so in the future?" David Southwood, ESA's director for science and robotic exploration, said in an ESA statement released Monday. NASA issued a parallel statement that quoted Associate Administrator Ed Weiler as saying the ESA-NASA project would "reduce duplication of effort, expand our capabilities and see results neither ever could have achieved alone."

The instruments on the probe, to be launched in 2016 on a NASA rocket, will include:

• Mars Atmospheric Trace Molecule Occultation Spectrometer (MATMOS): An infrared spectrometer to detect very low concentrations of molecular constituents of the atmosphere. Principal investigator: Paul Wennberg, California Institute of Technology. Participating countries: United States, Canada.
• High-resolution Solar Occultation and Nadir Spectrometer (SOIR/NOMAD): An infrared spectrometer to detect trace constituents in the atmosphere and to map their location on the surface. Principal investigator: Ann Vandaele, Belgian Institute for Space Aeronomy. Participating countries: Belgium, Italy, Spain, Britain, United States, Canada.
• ExoMars Climate Sounder (EMCS): An infrared radiometer to provide daily global measurements of dust, water vapor and chemical species in the atmosphere to aid the analysis of the spectrometer data. Principal investigator: John Schofield, Jet Propulsion Laboratory. Participating countries: United States, Britain, France.
• High-resolution Stereo Color Imager (HiSCI): A camera to provide four-color stereo imaging at 2-meter resolution per pixel over an 8.5-kilometer swath. Principal investigator: Alfred McEwen, University of Arizona. Participating countries: United States, Switzerland, Britain, Italy, Germany, France.
• Mars Atmospheric Global Imaging Experiment (MAGIE): A wide-angle multispectral camera to provide global images in support of the other instruments. Principal investigator: Bruce Cantor, Malin Space Science Systems. Participating countries: United States, Belgium, France, Russia.

The orbiter will also carry a European piggyback probe designed to demonstrate technologies for entry, descent and landing on Mars.

The next ExoMars mission, due for a 2018 NASA launch, will send out a European rover with a drill as well as a NASA rover capable of caching samples for future return to Earth. All this is supposed to blaze the trail for a U.S.-European sample return mission to Mars, intended for launch in the 2020s.

Feel free to chime in with your comments below, and click the links to learn more about life on Mars:

• Life on Mars, or merely static?
• Caves discovered on Mars
• Is Martian life on ice?
• 'Mermaid on Mars' explained
• Water found (and lost) on Mars
• Life on Mars, continued

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