InSight’s Drill – The Mole

The InSight team is trying to get the “Mole” to carry on sinking itself into the Martian soil. This image from NASA/JPL-Caltech on 25 July 2019.

Progress halted shortly after the probe was deployed. Speculation is the probe came upon a rock it could not compensate for.

A plan was devised and has been put into action. Will it work?

Basically the support structure was lifted out of the way by InSight revealing an interesting scenario and it could be a compaction problem:

NASA (click here): Scientists and engineers have been conducting tests to save the mole at JPL, which leads the InSight mission, as well as at the German Aerospace Center (DLR), which provided HP3. Based on DLR testing, the soil may not provide the kind of friction the mole was designed for. Without friction to balance the recoil from the self-hammering motion, the mole would simply bounce in place rather than dig.

One sign of this unexpected soil type is apparent in images taken by a camera on the robotic arm: A small pit has formed around the mole as it’s been hammering in place.

“The images coming back from Mars confirm what we’ve seen in our testing here on Earth,” said HP3 Project Scientist Mattias Grott of DLR. “Our calculations were correct: This cohesive soil is compacting into walls as the mole hammers.”

The team wants to press on the soil near this pit using a small scoop on the end of the robotic arm. The hope is that this might collapse the pit and provide the necessary friction for the mole to dig.

It’s also still possible that the mole has hit a rock. While the mole is designed to push small rocks out of the way or deflect around them, larger ones will prevent the spike’s forward progress. That’s why the mission carefully selected a landing site that would likely have both fewer rocks in general and smaller ones near the surface.

The robotic arm’s grapple isn’t designed to lift the mole once it’s out of its support structure, so it won’t be able to relocate the mole if a rock is blocking it.

The team will be discussing what next steps to take based on careful analysis. Later this month, after releasing the arm’s grapple from the support structure, they’ll bring a camera in for some detailed images of the mole.