NASA Scientists Try A New Approach To Free InSight Mars Lander's Stuck Thermometer

Oct 17, 2019
Originally published on October 28, 2019 7:16 am


A rescue appears to have taken place on the surface of Mars. NASA engineers announced today that they have salvaged - for now - a key part of one of their probes. NPR's Joe Palca has more.

JOE PALCA, BYLINE: NASA's probe called InSight is supposed to study the interior of Mars. One key instrument is called the mole. It's a kind of thermometer that was supposed to pound itself into the ground 16 feet, deep enough to measure the heat flow coming from the interior of the planet. In February, though, after digging just 14 inches, it stopped. Since then, engineers on Earth have been trying to come up with a strategy to get it moving again.

TROY HUDSON: For the first time in eight months, we have definitive forward progress.

PALCA: Troy Hudson is the instrument system engineer for the InSight mission.

HUDSON: The mole has moved forward about 2 centimeters, which to me definitively says there was not a rock in front of the mole. That had always been a possibility, and now I think that possibility has been eliminated.

PALCA: If it had been a rock, that would have been bad, bad news.

HUDSON: We could encounter another rock later on. But what stopped us from digging eight months ago was not a rock.

PALCA: So if it wasn't a rock, what did stop the mole from moving? Well, Hudson says it was the nature of the Martian soil. To move forward, there's a weight on a spring inside the mole that acts as a kind of pile driver, thumping on the mole to drive it downward. But the mole needs just a tiny bit of friction to allow it to move. Apparently, the Martian soil wasn't providing any, and all that pounding was completely useless. Luckily, the InSight lander has a robotic arm.

HUDSON: So we brought the robotic arm in and used the scoop on the end of it to push sideways against the mole. This drives it into the soil and increases the amount of friction resistance it experiences.

PALCA: That apparently did the trick. Now the mole is moving again but more slowly than engineers had expected. But they think they know why. All that ineffectual pounding only served to compact the soil beneath the mole. Hudson says once they get through that compact patch, things should pick up. At least that's the hope.

Joe Palca, NPR News.

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