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NASA pulls the plug on InSight's mole after Martian surface bests boffins

A blue day on the Red Planet

Hot on the heels of a mission extension comes news that scientists have now given up on attempts to persuade the NASA InSight lander's "mole" to burrow more than a few centimetres beneath the Martian surface.

Despite repeated attempts since February 2019, the mole has failed to achieve the depth necessary to conduct the desired science. The instrument hammered itself to a depth of approximately 35cm, but it appears the "duricrust" lurking beneath the surface has won the day.

The cemented soil of duricrust is unlike anything encountered before on Mars in previous missions, and not something the mole was designed for.

Rather than burrow into Mars, the instrument simply bounced around in its pit and attempts to bury and push it down with the assistance of InSight's robot arm have finally come to naught.

The team had one final go last week, having got the top of the mole two or three centimetres under the surface, but after using the scoop on the end of InSight's arm to scrape soil and tamp it down on top in an effort to improve friction an end was called. A further 500 hammer strokes from the mole had seen no further progress.

"We've given it everything we've got, but Mars and our heroic mole remain incompatible," said HP3's principal investigator, Tilman Spohn of the German Aerospace Center (DLR). He added that the lessons learned would benefit future missions.

"The mole is a device with no heritage. What we attempted to do – to dig so deep with a device so small – is unprecedented," said Troy Hudson, a scientist and engineer at NASA's Jet Propulsion Laboratory.

Hudson had led efforts to get the mole deeper into the Martian crust.

The InSight lander has two main science goals: to understand the formation and evolution of Mars and to determine the level of tectonic activity on the planet.

Part of NASA's Discovery programme, the lander includes a seismometer, a radio science experiment, and a Heat Flow Probe. Known as the Heat Flow and Physical Properties Package, HP3 for short, this "mole" was to burrow almost three metres beneath the Martian surface in order to measure the heat coming from the interior of the planet.

Still, InSight's other instruments continue to work as expected and, as seems to often be the case, the lander has exceeded longevity expectations. It has company on the Red Planet in the form of the long-lived Curiosity Rover, which recently celebrated its 3,000th day on Mars. NASA's Perseverance rover is due to reach the Martian surface on 18 February. ®

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