NASA’s sent its Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission to Mars so that it could deploy a suite of state-of-the-art instruments capable of assisting planetary scientists in their ongoing quest to accumulate vital information about the planet’s physical dynamics. Upon making a successful landing in November of 2018, InSight immediately began deploying its instruments.
Image Credit: NASA/JPL-Caltech
Among InSight’s most notably instruments are the Seismic Experiment for Interior Structure (SEIS), which measures marsquakes in an attempt to better understand their origins, the Heat Flow and Physical Properties Package (HP3), made to dig itself 16 feet beneath the surface to detect heat sources emanating from the planet’s center, and the Rotation and Interior Structure Experiment (RISE), which uses an X-band radio to ascertain important details about Mars’ planetary rotation and interior.
Most of InSight’s instruments deployed without a hitch, but the HP3 instrument, also sometimes referred to as ‘the mole’ for its digging characteristics, ran into trouble while attempting to dig beneath the planet’s surface. Rather than getting 16 feet under as it was supposed to, the instrument would continuously pop back up above the surface.
Mission scientists determined that the soil at the InSight landing zone was different than initially expected, and that the mole didn’t have enough friction while digging. As it would seem, the soil wasn’t quite as loose and sandy as it was thought to be, and there was more duricrust – a type of static cemented soil with little give.
Engineers worked around the clock in an attempt to resolve the problem, and a number of possible methods to get the mission back on track presented themselves. One method involved ‘pinning’ the InSight lander’s robotic arm against the side of the mole as it dug to help give it the friction it needed, while another involved pressing the robotic arm down directly on top of the mole as it dug.
NASA attempted the first of the aforementioned methods to no avail and avoided progressing to the second because it carries the risk of damaging fragile ribbon cables at the top of the instrument. With options becoming severely limited, it now seems like there may be no other option but to try pressing down on the mole as it digs.
Moving forward with this method could be a long and drawn-out process as NASA wants to avoid fraying the fragile cables. First, teams will attempt to position the robotic arm in such a way that it can avoid the cables as it presses down. Then, a brief test push will be commanded to see what happens. If everything goes according to plan, then the robotic arm could press down for longer durations to keep the mole from popping back out of the ground each time it attempts to dig.
Depending on the progress that this method brings to the mole’s digging, mission scientists could maintain pressure on the mole or look at other options. It should be interesting to see if the mole will finally get into place so that it can perform its intended job.