The mole is the burrowing part of the lander's Heat Flow and Physical Properties Package (HP3), an instrument designed to dig down deep and take Mars' internal temperature, much like a doctor doing a checkup. Mars was not a willing patient.
InSight landed in late 2018 and we've been following the mole's trials and travails ever since it first deployed in early 2019. The mole -- which was built by the German Aerospace Center (DLR) -- behaved like a little pile driver that uses a hammering motion to descend. But Mars wasn't having it. The mole kept backing out of its hole instead of digging down.
NASA and DLR tried all sorts of tricks, from pressing on the mole with InSight's arm to scooping soil onto it. The mole team made one final attempt to gain some ground last weekend, but the unexpected soil properties in InSight's landing area once again proved too much for it. The clumpy texture of the soil meant the mole couldn't get enough friction to burrow.
Now is the time to salute the mole, its team and the ingenuity put into the mission. Scientists have learned about the soil in this area of Mars and they developed new and sophisticated ways of using InSight's robotic arm. This knowledge will feed into future Mars exploration missions.