New push to salvage InSight Mars lander's heat probe
NASA is working to salvage the heat probe on the space agency's InSight Mars lander. The hope is that with the aid of the lander's robotic arm, the self-hammering probe can be freed from the stuck position it's been locked in since February 28.
Mission planners had high hopes for the InSight mission. The first dedicated geological lander to set down successfully on the Red Planet, its goal was to learn more about the deep structure of Mars and its interior dynamics.
Key to this is the heat probe or mole, which is a self-propelled drill designed to hammer itself down to a depth of 16 ft (5 m) and measure the temperature profile of the planet. Unfortunately, as it started to burrow down, it met an obstruction that stopped it cold at only 14 inches (35 cm) in.
At first, this seemed to be a buried boulder, but removing a support structure around the drill allowed mission experts to bring the camera on InSight's arm to bear, showing that there was a layer of hard, clumped soil or duricrust 2-4 inches thick that was holding up progress.
Because the drill hasn't enough friction to push forward, its hammering action just makes it bounce up and down. Worse, the probe isn't designed to be extracted, so NASA and the probe's builder, the German Aerospace Center (DLR), have no choice but to either find a way for the drill to get a purchase or abandoned it as is.
The plan now is to use a tactic called "pinning," which involves using the robotic arm's scoop to apply pressure to one side of the probe, pressing against one side of the drill hole. The hope is that this will generate enough friction for the drill to be able to hammer down through the duricrust.
"All we know about the soil is what we can see in images InSight sends us," says Tilman Spohn, HP3's principal investigator at DLR. "Since we can't bring the soil to the mole, maybe we can bring the mole to the soil by pinning it in the hole."
NASA has already made several tests using both InSight and a replica of the lander at the Jet Propulsion Laboratory in Pasadena, California. Results have been positive, though there is no guarantee that the hole won't simply collapse under pressure. In addition, engineers are also looking at the alternative of using the scoop to scrape soil into the hole to produce more friction.
"We're asking the arm to punch above its weight," says Ashitey Trebi-Ollennu, the lead arm engineer at JPL. "The arm can't push the soil the way a person can. This would be easier if it could, but that's just not the arm we have."
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