NASA InSight's 'Mole' Is Out of Sight

NASA's InSight lander continues working to get its "mole" - a 16-inch-long (40-centimeter-long) pile driver and heat probe - deep below the surface of Mars. A camera on InSight's arm recently took images of the now partially filled-in "mole hole," showing only the device's science tether protruding from the ground.

Sensors embedded in the tether are designed to measure heat flowing from the planet once the mole has dug at least 10 feet (3 meters) deep. The mission team has been working to help the mole burrow to at least that depth so that it can take Mars' temperature.

The mole was designed so that loose soil would flow around it, providing friction against its outer hull so that it can dig deeper; without this friction, the mole just bounces in place as it hammers into the ground. But the soil where InSight landed is different than what previous missions have encountered: During hammering, the soil sticks together, forming a small pit around the device instead of collapsing around it and providing the necessary friction.