NASA’s InSight mission on Mars has been full of success, for example, the detection of marsquakes over the last few months. But there have also been struggles. One of its instruments, nicknamed the mole, has not been able to successfully move into position. Now the mission team is trying a peculiar new approach.
The mole, or, more specifically, Heat Flow and Physical Properties Package (HP3), is a self-hammering heat probe. It is designed to burrow itself up to 5 meters (16 feet) below the surface. Unfortunately, since its placement on February 28, 2019, it has not been able to dig more than 35 centimeters (14 inches). The mission specialists are now using the lander's robotic arm to help to solve the issue.
The mole seems to be stuck on a particularly tough piece of soil and it doesn’t seem to be capable of getting enough friction to dig through. Friction is key to the mission's design. Without it, the self-hammering, as has been happening, makes the mole just bounce in its place as it recoils.
The team is ready to use a tactic called "pinning." The robotic arm of the lander will be used to steady HP3 and over the next few weeks, they hope that this approach might lead to some digging progress.
"We're going to try pressing the side of the scoop against the mole, pinning it to the wall of its hole," InSight Deputy Principal Investigator Sue Smrekar, of NASA's Jet Propulsion Laboratory, said in a statement. "This might increase friction enough to keep it moving forward when mole hammering resumes."
The mole found itself in peculiar soil. Based on the data reported by the sensors, HP3 encountered a strange layer of duricrust 5 to 10 centimeters (2-4 inches) thick. When the mole hammers down, the crust clumps rather than falling around the instrument, so the mole has not been able to penetrate this tough layer. This is unlike any soil previously encountered on Mars missions and the mole was not designed for it.
"All we know about the soil is what we can see in images InSight sends us," said Tilman Spohn, HP3's principal investigator at the German Aerospace Center (DLR). "Since we can't bring the soil to the mole, maybe we can bring the mole to the soil by pinning it in the hole."
The team will also use the robotic arm in another way. It will scoop up the soil (its original purpose) and pour it into the hole, hopefully increasing the friction. We hope that these two approaches will be enough for the mole to continue digging.