InSight’s mole digs an inch

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The InSight science team today tweeted that their attempt to use the lander’s robot arm to help the mole push downward in its effort to insert a heat sensor fifteen feet into the Martian interior has resulted in a gain of about an inch or three centimeters.

This success, small as it seems, is important in that it proves that the reason the drill had been stopped penetrating downward was not because of the presence of a rock, but because the drill hole had become so wide that the drill no longer had side friction to hold it in place. They are now using the arm to give the mole that friction.

The goal was to insert to heat sensor five meters or about sixteen feet into the ground. They are presently a little over a foot down. If this effort has really succeeded, they can then proceed to drill the remaining distance.

One issue however is whether the unexpected weak and porous nature of the soil, which allowed the hole to become so wide, might affect any data produced by the heat sensor. This is presently unknown, but it is a significant question that the scientists involved must ask. If the sensor ends up inside a very wide shaft that allows the surface environment to reach the sensor then it will not really be measuring the temperature of the Martian interior.



  • Charles

    I wonder why they don’t use the scoop to fill the hole.

  • Edward

    The problem was not just a lack of soil; there had been plenty of soil when it started digging. The problem is that the sooil was not compacted enough to provide the friction that the probe needed in order to hammer itself into the ground.

    The following video shows how the hammer works.

    The peen is driven upward against a spring, the spring accelerates the peen downward, then the peen hits the bottom (anvil) and the shock drives the probe down a small distance. The problem is that when the spring accelerates the peen downward, there is not enough friction with the surrounding ground to keep the whole probe from “jumping” upward, so the shock at the end of the stroke is virtually useless, because the probe is no longer solid enough against the ground. Indeed, the process caused more damage to the surrounding ground than to the dirt under the probe.

    Filling the hole would not provide sufficiently compacted soil around the probe. It would only provide loose soil.

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