NASA’s InSight lander has been studying the red planet for more than two years now. During that time, InSight has beamed back data on the planet’s seismic activity, weather, and even the sound of blowing wind. It was also supposed to relay data on the planet’s internal temperature, but NASA has announced that it’s giving up on that endeavor after being unable to get the heat probe to burrow into the fine Martian soil.
InSight made history when it arrived on Mars, deploying the first-ever seismic sensor (known as SEIS) on another planet. The team didn’t want to risk any mishaps, so they build a scale model of the landing zone to carefully plan out where they would deploy instruments. The SEIS package worked like a charm, but the heat Heat Flow and Physical Properties Package (HP3) never worked as intended.
The HP3, sometimes called the “mole,” is a self-hammering nail that was supposed to drag a cable of temperature sensors with it as it bored several meters into the planet’s crust. Early on, NASA found that the mole couldn’t get enough traction to burrow below the surface — it kept popping out (see above). The team tried several techniques to get the mole digging, like using the lander’s robotic arm to tamp down the soil around the hole and even pushing the probe directly. As recently as late 2020, NASA saw some progress — the HP3 was, for the first time, completely underground. Its luck didn’t hold, though.
NASA now says the soil at the Elysium Planitia landing site was too different than what NASA has encountered in the past. Each time the mole attempted to drive itself deeper, the slippery Martian soil would collapse inward and fill in the hole. As a result, even after using the arm to nudge the probe deeper, there was no way for it to continue its downward journey.
It’s not all bad news. The mission has returned invaluable data from its other instruments, and mission scientists have learned how variable Martian soil can be. The team has gained a great deal of experience using the lander’s robotic arm, too. NASA has just extended InSight’s mission by at least two years, so the team will be able to put that experience to good use. The next order of business is to bury the cable connecting the SEIS package to the lander. The added insulation should reduce cracking and popping sounds that currently pollute the seismic data.