WASHINGTON — NASA plans to take new steps later in June to try and resolve a problem with one of the key instruments on the Mars InSight lander.
In a June 5 statement, the Jet Propulsion Laboratory said it will use the lander’s robotic arm, designed to place instruments onto the Martian surface, to lift up the support structure for the Heat Flow and Physics Properties Package (HP3) as part of efforts to troubleshoot the instrument.
The instrument, placed on the Martian surface early this year, features a probe, or “mole,” designed to burrow to a depth as great as five meters below the surface in order to measure the heat flow from the planet’s interior. However, the probe has been stuck about 30 centimeters below the surface for the last three months.
Project scientists and engineers now believe that the mole is stuck because of a lack of friction with the surrounding regolith, which means the mole simply bounces in place when it attempts to hammer deeper into the surface. That appears to be a more likely possibility than either the mole hitting a rock it cannot push aside or a snag in the mole’s tether within the instrument’s housing.
“Snagging requires some specific movements of the mole that it may have performed but not likely so. Judging from the distribution of rocks on the surface, the likelihood of encountering a rock at the right depth was concluded to be only a few percent,” said Tilman Spohn, lead for the HP3 instrument at the German space agency DLR, in a June 6 blog post. “So we are left with the friction hypotheses being the most likely hypothesis and — importantly — the one that we can do something about to help the mole along.”
Engineers have proposed using InSight’s robotic arm to press down on the surface by the instrument, believing that the force will increase the friction enough to allow the mole to gain traction. Doing so, though, requires moving the support structure.
Current plans call for lifting the structure in three steps over the course of a week in late June, taking images after each step to check on the status of the mole. If the mole is removed from the ground during this process, it can’t go back in, effectively ending that instrument’s mission.
“We don’t want to take an action that makes the situation worse, so we’ve been moving very carefully,” said Troy Hudson, an engineer-scientist at JPL working on the mission, in a statement. “We want every action to be safe for HP3, the robotic arm and InSight’s seismometer, which is very close by.”
Spohn said the team hopes to have the “next steps” for troubleshooting HP3 decided by the middle of July. “After that, we will need time to run more tests.”