NASA’s attempt to burrow into Mars met 2 insurmountable obstacles: cement-like soil and an unexpected energy shortage

InSight mars lander
An artist illustration of the InSight lander on Mars, with its “mole” burrowed deep in the soil.

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.

mars insight mole heat probe skitch
The mole, halfway popped out of its hole, on October 26, 2019.

“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.”

An unexpected energy crisis

InSight lander mars
An artist’s concept shows NASA’s InSight lander with its instruments deployed on the Martian surface. The seismometer is the round device to the left of the lander.

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.

mars insight lander nasa solar panels dust
The InSight lander’s camera took this photo on July 18, 2020, showing one of its solar-panel arrays covered in 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.

Mars landing sites
The plain where InSight landed has presented challenges that other Mars missions didn’t face.

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.

A planet’s internal temperature reveals its history

If the mole had hammered down to 16 feet below, it would have measured temperatures all the way down its hole. That would allow scientists to calculate how much heat is leaving Mars – a metric called “heat flow.”

“It’s a single number, the heat flow, but it has ramifications for all kinds of aspects of understanding Mars,” Smrekar said.

Heat leaving a planet is, in part, warmth left over from its formation, but it also comes from decaying radioactive elements. Measuring the heat flow would tell scientists how much radioactive material is inside the Martian crust – the outer layer of the planet – versus the mantle beneath.

mars internal inner structure core mantle crust
An artist’s rendition of the inner structure of Mars: the topmost layer (crust), mantle, and solid inner core.

That would reveal not only how material was distributed when the planet formed (and whether it’s made of the same stuff as Earth), but also how the planet’s internal structure has changed over time.

“That goes back to understanding the early evolution of Mars, that time period when there was a lot of liquid water on the surface,” Smrekar said.

A higher concentration of radioactive material in the mantle would make that layer more active. More radioactive material in the crust could keep the planet’s upper layers warm.

Heat flow could also indicate how deep you’d have to drill into Mars to reach liquid water today. Underground water on the planet could still host microbial life. Future humans traveling to Mars will likely need to harvest water there.

Now there is no possibility of measuring the planet’s heat flow in the foreseeable future.

“I was hoping to get the data and be able to understand what that means for Mars,” Smrekar said.

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NASA has given up on its ‘Mars mole,’ a revolutionary experiment designed to burrow 16 feet and take the planet’s temperature

mars insight mole heat probe skitch
The InSight lander’s heat probe, or “mole,” poking out of the hole where it got stuck on October 26, 2019.

  • NASA is giving up on its Mars mole — a pile driver designed to hammer its way up to 16 feet below the Martian surface — after two years of trying to dig past cement-like soil.
  • Now the InSight lander won’t be able to take Mars’ internal temperature. 
  • The probe’s data would have helped piece together the planet’s history and its potential for microbial life.
  • Visit Business Insider’s homepage for more stories.

NASA has given up on its InSight lander’s “mole” after two years of trying to dig more than a few inches into Mars’ uncooperative soil.

The 16-inch-long pile driver was designed to hammer through the loose dirt that previous Mars missions had encountered. The soil would flow around the probe’s outer hull and provide friction to keep hammering deeper.

This way, the InSight team hoped, it would burrow up to 16 feet deep and take the planet’s temperature for the first time. Previous Mars landers had only scooped a few inches into the Martian surface.

The project would have revealed how much heat is leaving the red planet – warmth left over from Mars’ formation some 4.6 billion years ago. These measurements would help scientist reconstruct the planet’s history, as well as that of Earth and other rocky worlds. Internal heat can also come from decaying radioactive elements. Figuring out what’s inside Mars would help scientists determine whether it’s made from the same material as Earth.

InSight lander mars
An artist’s concept shows NASA’s InSight lander with its instruments deployed on the Martian surface.

What’s more, measuring the planet’s internal temperature could help scientists find underground reservoirs of liquid water, which could support microbial alien life or sustain future astronauts.

But the soil around InSight ended up being too clumpy and cement-like to provide the critical friction that the mole needed. On February 28, 2019, the InSight team realized that the device was simply bouncing in place as it hammered at the Martian crust.

By then, NASA had spent about $830 million on InSight, so it wasn’t prepared to give up on the groundbreaking new heat probe just yet.

However, after two grueling years of troubleshooting, the top of the mole is still just 2 or 3 centimeters below the surface. NASA announced Thursday that it was abandoning efforts to dig any further.

insight lander mole heat probe mars nasa
The hole where the InSight lander’s mole is buried, after its last hammering effort on January 9, 2021.

“After nearly two years of heroic effort on the part of the whole NASA InSight team, we now turn to the epilogue of the mole’s story,” Troy Hudson, a NASA scientist and engineer who led the troubleshooting efforts, wrote on Twitter. “Lots for me to process about this.”

In its extended mission over the next two years, InSight will listen for quakes on Mars and collect data on the planet’s rumblings with its seismometer. This can still teach scientists about the planet’s interior. Already, Mars quakes have revealed that the Martian crust is drier and more broken up than scientists previously thought ⁠- more like the moon than like Earth.

‘We’ve given it everything we’ve got’

As soon as the InSight team discovered a problem with the soil two years ago, it instructed the lander to move supporting gear out of the way. InSight lifted away the Heat Flow and Physical Properties Package (HP3) – a device containing all the engineering and mechanics that connect the mole to the lander – to make way for its multipurpose robotic arm.

insight mole heat probe mars nasa
An illustration of the InSight lander with its mole burrowed in the ground.

The only visible part of the mole was its tether, trailing out of the soil. The cable is lined with temperature sensors that would have collected data all the way down the mole hole.

To avoid touching this fragile tether, the InSight team tried using the robotic arm to press against the side of the mole, giving it some friction to dig down. Twice, the mole bounced back, shooting about halfway out of the dirt. It took until October 2020 to get the probe fully back into the ground.

mars insight mole
InSight’s mole backed about halfway out of the hole it had burrowed on October 26, 2019.

Then the robotic arm tried a new technique: scooping dirt on top of the mole hole and tamping it down, in an effort to provide the friction needed to burrow. After the probe conducted 500 fruitless hammer strokes on January 9, it became clear that the mole wasn’t digging any deeper.

“This was disappointing news to have when the images came down over the weekend, but it was an amazing process working with all these engineers trying to figure this out,” Mark Panning, a seismologist on the InSight team, wrote on Twitter.

“We’ve given it everything we’ve got, but Mars and our heroic mole remain incompatible,” Tilman Spohn, the principal investigator for the mole, said in a press release. “Fortunately, we’ve learned a lot that will benefit future missions that attempt to dig into the subsurface.”

The crisis forced the InSight team to use the lander’s robotic arm in new and creative ways – an experience that could be handy for future interplanetary missions. The team now plans to use the arm to bury the tether connecting the lander to its seismometer. That should reduce background noise in its quake readings.

“The mole is a device with no heritage. What we attempted to do – to dig so deep with a device so small – is unprecedented,” Hudson said in the press release. “Having had the opportunity to take this all the way to the end is the greatest reward.”

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