DLR developed for ESA the subsurface penetrometer or “Mole” as part of the Beagle 2 Mars lander. The Mole advances into the soil by an internal slammering hammer system driven by a small electric motor and a gear reduction unit. To achieve the required reduction ratio of 280 a train of 4 planetary gears is used, involving more than 20 gears. The Mole is here seen in laboratory during development and under test in simulated Mars landscape.