Mars InSight Lander's mole is digging into the dirt again

[Robert Zwilling]

Took 8 months to get InSights digger digging again. A clear case for mobile robots to accompany planet landers.
The mole, or burrowing device was trying to position a temperature sensor around 5 meters underground. It had stopped after going around a foot. A big rock was one possible cause, or very hard packed dirt. In June scientists removed the cover from the mole unit so they could watch it work. There was no rock, the hammer just couldn't stick to the ground it was pounding into. It was just pounding rarefied air. It is making contact with the ground again and digging into the ground. One article said the lander was using one of it's arms to pound the hammer into the ground. The old fashioned way to fix mechanical things that are acting up, give it a good smack. More likely the arm is just pressing the hammer into the surface to overcome the lack of friction.

No reason given why the hammer is bouncing. Could be the material under the surface is too soft or too flexible to absorb the shock, or too hard, and the hammer bounces off of it. If it was very soft or very loosely packed that could make tunneling easier. Dig a hole, then bury everything under what was dug up and put a cap over it for shielding.

At least 21 Marsquakes detected so far by the lander. The data from the quake information will be used to approximate how the planet is formed and the structure of the core. Apparently the underground temperature is needed to better understand the quake data. Probably speed of sound/shock waves in Martian crust can't be well established without temperature of the ground.

 

[Parson]

Thanks for the interesting info. @Robert Zwilling

 

[J Riff]

This belongs on a SF site. )

 

[Nozzle Velocity]

One article said the lander was using one of it's arms to pound the hammer into the ground. The old fashioned way to fix mechanical things that are acting up, give it a good smack. More likely the arm is just pressing the hammer into the surface to overcome the lack of friction.

No reason given why the hammer is bouncing. Could be the material under the surface is too soft or too flexible to absorb the shock, or too hard, and the hammer bounces off of it.

I've been following this one. The dirt was softer than expected, causing the diameter of the hole to be so large that the drill couldn't maintain its friction, causing it to just bounce around. They pulled the drill out, looked at the hole and saw the problem. They put the drill back in and began using the scoop on the end of the robot arm to fill in the hole around the drill. They started that back in June. And you're right, there's no hammering. They're now using that same scoop arm to press the drill into the side of the hole so it can maintain its grip. They had gone an inch when they tweeted out that it was working.

I didn't think this hurdle would be overcome, so this is amazing. But it's going to be a long five meters! If the ground becomes more solid at a lower depth, the drill should start working better. If not, that's a lot of loose, porous dirt and will possibly bring into question the accuracy of temperature readings at any level. It would seem optimal to have the probe sealed off with no atmospheric influence from the surface.

 

[Pemry Janes]

Which is an argument that you'd want an operation like this to be more mobile. Pin point accuracy isn't possible and if the spot you land on isn't ideal, with a lander you can't scoot over to a better spot.

 

[Nozzle Velocity]

It seems like I remember hearing that they wanted a more stable platform for the seismometer or the drill or something - probably the drill - so it has legs instead of wheels. They actually landed where they wanted. It was a risky spot and close to some rocky areas, but they were confident that it was the site they needed based on the surveys from the Mars Orbiter. I'll bet they re-think this design. As it is, they may still hit a rock before they get to five meters. And five meters is optimal, not crucial, so they may still get good data at some point.

 

[reiver33]

I’ll go fix it, but I charge mileage...

 

[Robert Zwilling]

Thinking it over now, the data from drilling 15 feet into Mars might be more a lot more important than the mission seems to be making it.

 

[Nozzle Velocity]

I looked up the info on the heat probe designed by the Germans and there is actually hammering after all. They call it "self hammering" to be precise. But the principle is the same as the drill. Without a narrow hole, the probe just bounces around. When this started working again, I'll bet those German engineers celebrated by getting "self hammered".

 

[Robert Zwilling]

Absolutely

 

[Nozzle Velocity]

Aaaand it bounced halfway out of the hole just when things were hammering right along. Speculation is that dirt was falling in the opposite side of the probe and filling up the hole again. This probe is being called "not Level 1", meaning not critical for mission success. Apparently the seismometers were the priority. In this photo you can see the scoop on the right and the probe on the left. Notice how far the probe is leaning. That's some really loose dirt!

 

[Parson]

Isn't it often the small unexpected things that cause the most frustration?