NASA spacecraft out looking for ‘Marsquakes’
What do you call an earthquake when it happens on Mars?
This is not the opener to a nerdy joke. It’s a central question facing NASA’s newest spacecraft, InSight.
The probe is slated to launch early Saturday morning, carrying instruments to take the temperature and pulse of the Red Planet’s deep interior. Even the subtlest shake – known, yes, as a marsquake – could carry clues about how the planet formed and what goes on today beneath its surface.
Most intriguing of all, InSight aims to help scientists understand why Earth and Mars, which formed from the same primordial ingredients more than 4.5 billion years ago, now look so different.
“Earth has plate tectonics, so its initial crust is essentially gone, it’s all been recycled,” explained Suzanne Smrekar, the mission’s deputy principal investigator. “Mars gives us an opportunity to see the materials, the structure, the chemical reactions that are close to what we see in the interior of Earth, but it’s preserved from the first 10 million years [of the solar system]. It gives us a chance to go back in time.”
InSight is scheduled to launch from Vandenberg Air Force Base in California. It will be NASA’s first interplanetary launch from the West Coast, and if all goes according to plan, it will be the first mission to study seismic waves on another planet. (NASA tried, and failed, to do this with its twin Viking landers in the 1970s.)
The probe will have company atop its Atlas V launch vehicle: two briefcase-sized satellites called Mars Cube One, or MarCO. The twin spacecraft will fly behind InSight on its 300-million-mile, six-month journey, allowing NASA to test new, miniaturized deepspace communication equipment. If they make it to the planet, they can relay back data from InSight as it plunges through the Martian atmosphere and touches down on the surface.
InSight’s ability to send back science data does not depend on the success of the MarCO satellites, though. The Mars Reconnaissance Orbiter, which has circled Mars since 2006, also will be recording broadcasts from the lander.
But success “means that when we land on Mars in the future, we can choose to have something like MarCO go with it, and we’d be able to land in places that the orbiter might have a hard time hearing the landing happening,” said Joel Krajewski, an engineer at the Jet Propulsion Laboratory and the project manager for MarCO. “And we can contemplate doing this kind of relay for missions to other bodies that right now don’t have orbiters around them to serve this useful function.”
After touching down, InSight, which stands for “Interior Exploration using Seismic Investigations, Geodesy and Heat Transport,” will spend the next two years sitting patiently in the middle of Elysium Planitia, a vast, flat plain near the Martian equator.
The lander’s dome-shaped seismometer resembles the tools used to detect quakes on Earth. But the biggest seismic waves on this planet are generated by tectonic plates drifting and colliding. Tremors on Mars – if they happen – are likely caused by its cooling.
The ultrasensitive instrument also can detect seismic rumblings of other origins: the thump of a meteorite impact, shivers produced by dust storms.
Whatever the source, the seismic waves that ripple through the planet will be distorted by changes in the materials they encounter. InSight’s seismometer is capable of detecting those distortions, giving scientists insight (get it?) into lingering questions about the planet’s interior: Where is the boundary between crust and mantle? Are there plumes of active volcanoes or reservoirs of liquid water hiding beneath the surface?
Another instrument, the Heat Flow and Physical Properties Probe, will drill almost 16 feet into the planet’s surface – farther than any craft has dug. Its goal is to measure the geothermal heat coming out of Mars as a result of radioactive decay.