NASA InSight’s ‘Mole’ no longer digging the red planet

News release from NASA's Jet Propulsion Laboratory

An artist’s impression of NASA’s Mars Insight lander on the surface of the red planet. An ultra-sensitive seismometer is depicted on the surface at left with a German heat probe at right. Image: NASA/JPL-Caltech

The heat probe developed and built by the German Aerospace Center (DLR) and deployed on Mars by NASA’s InSight lander has ended its portion of the mission. Since 28 February 2019, the probe, called the “mole,” has been attempting to burrow into the Martian surface to take the planet’s internal temperature, providing details about the interior heat engine that drives the Mars’ evolution and geology.

But the soil’s unexpected tendency to clump deprived the spike-like mole of the friction it needs to hammer itself to a sufficient depth.

After getting the top of the mole about 2 or 3 centimetres under the surface, the team tried one last time to use a scoop on InSight’s robotic arm to scrape soil onto the probe and tamp it down to provide added friction. After the probe conducted 500 additional hammer strokes on 9 January, with no progress, the team called an end to their efforts.

Part of an instrument called the Heat Flow and Physical Properties Package (HP3), the mole is a 16-inch-long (40-centimeter-long) pile driver connected to the lander by a tether with embedded temperature sensors. These sensors are designed to measure heat flowing from the planet once the mole has dug at least 10 feet (3 metres) deep.

“We’ve given it everything we’ve got, but Mars and our heroic mole remain incompatible,” said HP3’s principal investigator, Tilman Spohn of DLR. “Fortunately, we’ve learned a lot that will benefit future missions that attempt to dig into the subsurface.”

While NASA’s Phoenix lander scraped the top layer of the Martian surface, no mission before InSight has tried to burrow into the soil. Doing so is important for a variety of reasons: Future astronauts may need to dig through soil to access water ice, while scientists want to study the subsurface’s potential to support microbial life.

“We are so proud of our team who worked hard to get InSight’s mole deeper into the planet. It was amazing to see them troubleshoot from millions of miles away,” said Thomas Zurbuchen, associate administrator for science at the agency’s headquarters in Washington.

“This is why we take risks at NASA – we have to push the limits of technology to learn what works and what doesn’t. In that sense, we’ve been successful: We’ve learned a lot that will benefit future missions to Mars and elsewhere, and we thank our German partners from DLR for providing this instrument and for their collaboration.”