RIP InSight: Dust shuts off NASA marsquake detector after 4 years
By Kenneth Chang
NASA’s Mars InSight spacecraft is dead.
For months, mission managers have been expecting this as dust accumulated on the lander’s solar panels, blocking the sunlight the stationary spacecraft needs to generate power.
InSight, which arrived on the surface of Mars more than four years ago to measure the red planet’s seismological shaking, was last in touch Ddec. 15. But nothing was heard during the last two communication attempts, and NASA announced Wednesday that it was unlikely for it ever to hear from InSight again.
“I feel sad, but I also feel pretty good,” Bruce Banerdt, the mission’s principal investigator at NASA’s Jet Propulsion Laboratory, said in an interview. “We’ve been expecting this to come to an end for some time.”
He added, “I think that it’s been a great run.”
InSight — the name is a compression of the mission’s full name, Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport — was a diversion from NASA’s better known rover missions, focusing on the mysteries of Mars’ deep interior instead of searching for signs of water and possible extinct life on the red planet. The $830 million mission aimed to answer questions about the planet’s structure, composition and geological history.
Mars lacks plate tectonics, the sliding of pieces of crust that shape the surface of our planet. But marsquakes occur nonetheless, driven by other stresses such as the shrinking and cracking of the crust as it cools.
The mission’s final year proved particularly eventful, as its instruments detected vibrations from a sizable space rock, 15 to 40 feet in diameter, hitting Mars 2,000 miles away from the spacecraft on Christmas Eve last year. NASA’s Mars Reconnaissance Orbiter was then able to photograph the new crater and chunks of underground ice that were kicked up to the surface by the impact. That ice discovery was closer to the equator than any spotted previously, a potential resource for future astronauts.
In May, InSight measured a marsquake registering 4.7 magnitude, the largest of the mission.
The spacecraft’s seismometer lived up to scientists’ expectations. It was the first time that quakes have been detected on another planet. (It was, however, not the first off-Earth quakes. During the Apollo missions, NASA astronauts left seismometers on the moon, and those registered numerous moonquakes.)
The seismic waves bouncing around the interior of Mars essentially provided a sonogram of the planet, offering new details about the crust, mantle and core.
This was the biggest result of the mission, Banerdt said, “to actually map out the deep interior of the planet.”
The crust below InSight turned out thinner than expected, about 15 to 25 miles. The red planet’s core is still molten, somewhat a surprise to scientists because Mars is much smaller than Earth. The core is also larger than expected — 1,120 miles in diameter — and less dense than predicted, which points to lighter elements mixed in with the iron. Those elements would lower the melting point, which could help explain why the core is not solid.
The geological structure helps scientists understand how quickly heat is seeping out of Mars, and that in turn helps them reconstruct what the surface may have been like several billion years ago and how habitable the surface may have been back then.
“We broke new ground, and our science team can be proud of all that we’ve learned along the way,” Philippe Lognonné of Institut de Physique du Globe de Paris, principal investigator of InSight’s seismometer, said in a statement from NASA.
However, a second instrument, which was designed to burrow 16 feet underground, was never able to go far beneath the surface, foiled by unexpectedly clumpy soil. The device, nicknamed “the mole,” was to measure heat flow coming from the deep interior of Mars.
“That was a big disappointment,” Banerdt said.
Other instruments on InSight measured Martian weather and remnants of an ancient magnetic field that are preserved in the rocks.
Banerdt said it was still possible that InSight could pop back to life, especially if one of the small dust devil cyclones that skitter across the Martian landscape passes over the spacecraft and cleans off the dust.
If the solar panels can charge up the batteries, InSight would try to restart and try to get back in touch. Radio transmissions from a revived InSight could show up as interference in communications sent from other NASA spacecraft at Mars.
“If we start seeing that signal consistently, that would tell us that perhaps InSight is back in business,” Banerdt said.
As InSight comes to an end, one of the other active NASA spacecraft on the surface of Mars, the Perseverance rover, is setting the stage for a future mission. It has started dropping onto the ground 10 tubes containing rock samples that are about the size of a stick of chalk.
Perseverance has been drilling a variety of rocks in the Jezero Crater where it landed. A follow-up mission still in the planning stages, Mars Sample Return, is to bring the rocks back to Earth for scientists to study in their laboratories.
The rover is still carrying other tubes — for the rocks drilled so far, two samples have been drilled — and the plan is for the rover to bring the sample tubes to the Mars Sample Return lander.
The samples that are being dropped on the ground now are in essence a backup in case something goes wrong with Perseverance before the Mars Sample Return lander gets there. In that case, the plan would be for the lander to set down near the samples that Perseverance had already dropped, and then helicopters, similar to the Ingenuity Marscopter that is currently accompanying the rover, would retrieve the samples.