Lunar exploration: Astronaut Schmitt standing next to a huge boulder on the Moon, during the Apollo 17 mission. This view looks across the Taurus-Littrow valley. The thin, pale streak to the right of the top of the boulder was the landing site of Apollo 17 on 11 December 1972. Schmitt was the first (and so far only) professional geologist to visit the Moon, although all lunar astronauts had to complete extensive training in the subject. Schmitt and fellow astronaut Eugene Cernan were on the Moon for 75 hours. During that time they made three excursions on the surface totaling 22 hours and covering 29 kilometers in their Lunar Roving Vehicle.