NASA's Plan To Rescue InSight's Stuck Heat Probe Appears To Be Working

A recent test of the heat probe resulted in 3 centimeters (1.1 inches) of progress. (Gif: NASA/InSight)

After being stuck for months, the InSight lander’s heat probe has managed to dig down a few centimetres into the Martian dirt. It’s a positive sign that the probe didn’t hit a rock as engineers originally feared and that a newly devised strategy to remedy the situation is actually working.

In this latest test, the heat probe managed to progress about 3 centimetres. That’s not a huge distance by any measure, but it’s a massive leap for the InSight team, which has been grappling with this thorny problem since late February.

Built by the German Aerospace Centre (DLR), the Heat Flow and Physical Properties Package (HP3) is designed to measure the heat emanating from beneath the Martian surface. The probe component of HP3, dubbed the “mole,” was expected to descend down to a depth of around 5 metres, but it didn’t get any further than 35 centimetres before it simply stopped.

Fears quickly emerged that the mole had struck a rock. If true, that would’ve signified the end of the HP3 mission, as the probe cannot be pulled out and relocated.

This past winter, however, new evidence emerged suggesting the mole hadn’t struck a rock but rather some dense material. Invigorated with hope, the InSight team devised a new strategy in an attempt to restore friction between the mole and the ground material — a requirement for the probe’s forward motion (otherwise the mole just bounces around in place like a pogo stick). To get the needed friction, the team used the InSight lander’s robotic claw to pin the mole against the wall of the shallow hole.

Excitingly, this strategy appears to be working, according to a tweet put out by the German Aerospace Agency.

“Good news from #Mars! Confirmed!,” exclaimed the agency in the tweet. “After 3 cm progress, it appears the @DLR_de ‘Mole’ on @NASAInSight was not stopped in its tracks by a rock under the Martian surface but had in fact lost friction.”

Looking at the animated video (above), the mole appears to be holding steady in place thanks to the robotic claw, and it’s clearly progressing downward. It actually looks really great, even if it’s small process.

A tweet from the NASA InSight account echoed the pronouncement: “With an assist from my robotic arm, the mole is digging again! We are just starting this new campaign, and are hopeful we can continue to dig.”

Not much more is known beyond these tweets, but an astute commenter asked if the attached cable, which is spinning along with the mole, might pose a problem as the probe gets deeper.

“We’ve noted the spin,” replied DLR. “It’s roughly 10° per 2cm. In the testbed we’ve seen a rotation by 270° for 5m. We’re watching the present situation w/ care being confident that the rotation will be reduced once tether is in ground. It’s expected to act as a ‘fin’ slowing the rotation down.”

So, that’s a big “phew.” The heat probe is a key component of InSight’s mission to study the interior of Mars, and it would have been extremely disappointing if it had failed altogether. Hopefully these precious few centimetres of progress represent a sign of success to come.

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