NASA will be landing on Mars again. Just weeks after the successful landing of the Mars rover Curiosity, NASA on Monday announced that it had selected a mission that in 2016 would land near the equator of Mars in order to listen to the tremors rumbling through the planet’s interior. The US$425-million mission, called InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) could expect to hear quakes as large as magnitude 4.5 or 5 in its two-year mission.

InSight beat out a mission to float on a hydrocarbon sea of Saturn’s moon Titan, and a mission that would have hopped on the surface of a comet. All three were “very compelling”, says NASA science chief John Grunsfeld. “The only disappointing thing is we can’t select them all to go on,” he says.

A month ago, Nature profiled each of the three finalists in NASA’s low-cost Discovery competition, as well as explored the consequences of a slowing cadence of mission launches.

At the time, the principal investigator, Bruce Banerdt, of the Jet Propulsion Laboratory in Pasadena, California, told me that in spite of the long history of Mars exploration, only the surface had been scratched. There are multiple National Academies studies that point to the need to get below the surface, he says. “There’s been a consistent drumbeat for 35 years that we need to study the interior of Mars,” he says. The mission should greatly reduce the uncertainty bounds on the thickness of the Martian crust  — potentially illuminating how Mars, in its early history, differentiated into a core, mantle and crust. It could also set limits on the size and density of the Martian core  — which in turn could help to explain the history of the planet’s magnetic dynamo.

Banerdt pointed out the misconception that you needed an array of two or more seismometers to study tremors. With new seismological techniques, he says, a single lander is enough. The mission relies on the same basic spacecraft design used by the Phoenix lander mission in 2008.

Image: NASA/JPL