NASA sent its InSight lander to Mars with an ambitious mission: to study the planet’s deep internal structure. A crucial piece of that effort – the “mole” – has failed despite two years of attempts to salvage it.
The mole is a revolutionary heat probe designed to burrow 16 feet into the Martian soil and take the planet’s temperature. Its measurements would have revealed clues about how the planet formed and has changed over the last 4.6 billion years – a history that would help scientists track down Martian water, and possibly life.
But the mole has made little progress in the unexpectedly thick soil. Now the InSight team must ration the lander’s solar power. NASA announced Thursday that the mole won’t be able to dig its hole.
“It’s a bit of a personal tragedy,” Sue Smrekar, a lead scientist on the InSight team who has spent 10 years working on the mole, told Insider. “Everyone tried as hard as they could make it work. So I can’t ask for anything more than that.”
No other Mars mission in NASA’s foreseeable can take the internal temperature measurements for which the mole was designed.
“This has been our best attempt to get that data,” Smrekar added. “From my personal standpoint, it’s super disappointing, and scientifically it’s also a very significant loss. So it feels really like a huge letdown.”
The InSight team spent two years maneuvering the lander’s robotic arm to see if it could help the mole burrow further. The probe, a 16-inch-long pile driver, is designed to leverage the loose dirt that other Mars missions have encountered. The soil would flow around the mole’s outer hull and provide friction to keep hammering deeper.
But in February 2019, the mole found itself bouncing in place on a foundation of firm soil called “duracrust.” The next two years were spent troubleshooting, beaming new software to InSight to teach its robotic arm new maneuvers to assist the mole, and anxiously waiting for photos that might show progress. “It’s just been a huge effort across the board, and one that we never anticipated,” Smrekar said. “We thought that we were going to punch the hole down.”
The InSight team first instructed the robotic arm to push on the mole, but that just caused it to pop out of the hole. Once they got the probe back in the ground, a year later, they instructed the arm to pile dirt on top of it, hoping that would provide enough friction for the probe to dig deeper.
But the mole made no progress with 500 hammer strokes last Saturday. The top of it was just 2 or 3 centimeters below the surface.
By then, InSight’s problems were compounding. Unlike other sites where NASA has sent rovers and landers, the open plain where InSight sits wasn’t having powerful gusts of wind. Smrekar calls such gusts “cleaning events,” since they blow the planet’s pervasive red dust off any robots in the area. Without them, InSight’s solar panels have accumulated a significant layer of dust.
At the same time, the seasons were changing and InSight’s home on a flat plain near Mars’ equator was getting colder. In the chill, InSight will require more energy just to stay functional, even while its solar panels are absorbing less sunlight than they should.
“Power is decreasing and so we’re coming up on a time period where, for probably two or three months, we’re probably going to have to stand down from doing instrument operations for awhile and just kind of go into survival mode until it gets warmer on Mars,” Smrekar said.
With this new time constraint, Saturday’s hammering attempt was the mole’s last chance to burrow.
Over the next two years, InSight will still listen for quakes on Mars and collect data on the planet’s rumblings with its seismometer. This can provide some insight about the planet’s interior. Already, Mars quakes have revealed that the Martian crust is drier and more broken up than scientists had thought - more like the moon than like Earth.