After nearly two years of struggles, NASA has abandoned efforts to deploy a heat flow probe for its InSight lander on the surface of Mars.
In a statement Jan. 14, NASA said a final attempt to drive the “mole” into the Martian surface Jan. 9 made no progress. The mole made 500 hammer blows and attempted to sink into the surface, but remained in place only two to three inches below the surface.
“We gave it our all, but Mars and our heroic mole remain incompatible,” said Tilman Spohn of the German space agency DLR, the principal investigator of the package officially known as the Heat Flow and Physical Properties Package (HP3). , in a statement released by NASA.
HP3 was designed to dig up to five meters deep into the surface and collect data on the heat flow inside Mars. The lander brought the instrument to the surface in early 2019, shortly after InSight landed on Mars in November 2018.
The probe, however, encountered problems shortly after the hammering started, when the mole stopped about a foot inside the surface. Scientists initially speculated that the probe had hit a rock or a harder subsurface 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 pitched and held it in place. At times, the mole appeared to partially withdraw from the hole.
Subsequent attempts consisted of moving the instrument case across the surface to expose the mole protruding from the hole. The spacecraft controllers used the bucket on the end of the lander’s robotic arm to push on the mole to prevent it from bouncing off, to plug the regolith around the hole, and also to fill the widening hole so that the mole could gain more friction.
While these efforts succeeded in getting the mole completely below the surface and covered with a few inches of regolith, the additional hammering efforts did not allow any progress, leading to the decision to leave the mole where it is. Project scientists concluded that the soil at the InSight landing site had different characteristics than those of other landers, which were used to guide the instrument’s design.
“We are very proud of our team who worked hard to get InSight’s mole deeper into the planet. It’s been amazing to see them troubleshoot millions of kilometers away, ” Thomas Zurbuchen, associate administrator for science at NASA, said in the statement. “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 using the mole came less than a week after the agency announced it would extend InSight’s mission through the end of 2022. At the time, NASA said this The extended mission “could continue (low-priority) use of the mole,” but did not discuss the duration of that effort.
InSight’s other main instrument, a seismometer, continues to work well, measuring earthquakes on Mars. “InSight’s extended mission will focus on producing a long-lived, high-quality seismic data set,” NASA said in its Jan. 8 announcement of the extended mission. Now that the mole’s deployment efforts are 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 weather data that will continue to function during the extended mission.
Despite the mole’s inability to burrow into the surface, NASA continues to provide useful engineering data that can be used for future missions that need to drill into the surface. While no such mission is currently in development, NASA is planning future missions, both robotic and human, using exercises to probe beneath the surface, including access to subsurface ice deposits.
“Fortunately, we learned a lot that will benefit future missions that try to dig underground,” Spohn said.