New Mars Orbiter Will Be a Super-Sniffer

The first joint U.S.-European mission to Mars now has a plan for its toolkit.

Scheduled for launch in 2016, the ExoMars Trace Gas Orbiter will study the chemical composition of Mars' atmosphere with a suite of instruments specially suited to the task. These instruments are expected to  take measurements 1,000 times more sensitive than those by previous Mars orbiters.

"To fully explore Mars, we want to marshal all the talents we can on Earth," said European Space Agency scientist David Southwood.

The selection of the orbiter's tools, which are being developed by both ESA and NASA, was announced Tuesday. The tools will include:

• Two spectrometers that will detect very low concentrations of molecules and map their locations on the planet's surface.
• An infrared-sensitive radiometer that will continuously measure dust, water and chemicals in the atmosphere as a basis for the spectrometric data.
• One camera that will provide 4-color simultaneous images of a 5.3-mile (8.5-kilometer) chunk of space, and another that will provide wide-angle images of the entire planet, across a range of wavelengths of light, to support the other instruments.

Traveling around Mars in a circular path, the ExoMars spacecraft will record spectra of the sun as its telescope picks up the light that reaches it through orbital sunrise and sunset. Depending on the composition of gas in the atmosphere, sunlight will pass through it differently.

"If you take the spectra fast," said NASA Jet Propulsion Laboratory researcher Geoffrey Toon, "you can measure the gas abundance at many different heights above the planet ? 70 measurements as the sun rises, and 70 as it sets."   

The study of trace gases, especially methane, follows a general quest to determine the planet's status as a potential habitat for past or present organisms.

"We got our first sniff of the gas with Mars Express in 2003; NASA has since clearly confirmed this," said Southwood, ESA's director of science and robotic exploration. "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??

Methane is released in both biological and geological processes, said California Institute of Technology researcher Paul Wennberg. Figuring out where Mars' methane comes from will help scientists better understand the history of the planet.

The orbiter's prime spectrometer, MATMOS (short for Mars Atmospheric Trace Molecule Occultation Spectrometer), will be sensitive enough to detect concentrations of gas down to parts per trillion ? so if just a few molecules of methane are hiding among 1 trillion molecules of other gases in the atmosphere, this instrument will be able to sniff them out.

"We did a calculation which shows that the microbial community found in three cows? bellies would produce an amount of methane that, in the Mars atmosphere, would be observable by MATMOS," said NASA Jet Propulsion Laboratory researcher Mark Allen, also at Caltech.

Other substances being targeted ? carbon-, sulfur- and nitrogen-containing molecules, as well as sulfur dioxide and hydrogen sulfide ? are similarly "diagnostic of active geological and biogenic activity" said Wennberg, who is the lead researcher of the MATMOS team. 

"Independently, NASA and ESA have made amazing discoveries up to this point," said Ed Weiler, associate administrator of NASA's Science Mission Directorate in Washington, D.C. "Working together, we'll reduce duplication of effort, expand our capabilities and see results neither ever could have achieved alone."

In addition to the Trace Gas Orbiter, the 2016 mission will include sending a vehicle to conduct observations and experiments on the ground.

In 2018, a pair of rovers, one European and one American, will take another crack at the Martian surface with a drill and a catching apparatus for bringing samples back to Earth.

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