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WASHINGTON – After nearly two years of struggle, NASA has abandoned efforts to deploy a heat flow probe to its InSight lander on the surface of Mars.
In a Jan. 14 statement, NASA said that a final effort to drive the “mole” into the surface of Mars on Jan. 9 made no progress. The mole made 500 hammer blows, trying to squeeze into the surface, but remained in place just two to three centimeters below the surface.
“We’ve given it all we have, but Mars and our heroic mole remain incompatible,” said Tilman Spohn of German space agency DLR, the principal investigator of what is officially known as Heat Flow and Physical. Properties Package (HP3), in a statement from NASA.
HP3 was designed to dig up to five meters deep into the surface, collecting data on the heat flux of the Martian interior. The lander brought the instrument set to the surface in early 2019, shortly after InSight landed on Mars in November 2018.
The probe, however, encountered problems shortly after the start of the hammering process, when the mole came to rest about one foot in the surface. Scientists first speculated that the probe had struck a rock or a harder underground layer.
The instrument team later determined that the problem was a lack of friction between the probe and the surrounding regolith, which caused the mole to bounce as it pounded, holding it in place. Sometimes the mole seemed to partially retreat out of the hole.
Subsequent efforts were to move the instrument case over the surface, revealing the mole coming out of the hole. The spacecraft controllers used the shovel on the end of the lander’s robotic arm to press down on the mole to prevent it from bouncing, tamp the regolith around the hole and also to fill the widening hole so that the mole can gain more friction.
While these efforts were successful in getting the mole completely below the surface and covering it with a few inches of regolith, further hammering efforts made no progress, which led to the decision to leave the mole where she is. Project scientists concluded that the soil at InSight’s landing site had properties different from those seen by other landers, which were used to guide the design of the instrument.
“We are very proud of our team who have worked hard to bring InSight’s mole deeper into the planet. It was amazing seeing them troubleshooting millions of miles away, ”said Thomas Zurbuchen, NASA Associate Administrator for Science. “That’s why we take risks at NASA – we have to push the boundaries of technology to know what works and what doesn’t.”
The decision to stop deploying the mole came less than a week after the agency announced it was extending InSight’s mission until the end of 2022. At the time, NASA said that the extended mission “may continue the (low priority) deployment” of the mole, but did not discuss the duration of those efforts.
InSight’s other main instrument, a seismometer, continues to perform well, measuring Martian earthquakes. “InSight’s extended mission will focus on producing a long-lasting, high-quality seismic dataset,” NASA said in its Jan. 8 announcement of the extended mission. With the mole’s deployment efforts now complete, the spacecraft will use its robotic arm to partially bury the cable between the seismometer and the lander, reducing thermal noise in its data.
InSight also has an instrument that collects meteorological data, which will continue to function during the extended mission.
Despite the mole’s inability to burrow into the surface, NASA said it is still providing useful engineering data that can be used for future missions that need to drill into the surface. While no such mission is currently under development, NASA is planning future missions, both robotic and human, using exercises to probe below the surface, including to access underground ice deposits.
“Fortunately, we’ve learned a lot that will benefit future missions that attempt to dig underground,” Spohn said.
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