The site was chosen because it had geologic features promising a varied collection of images, samples, and other data from both ancient highland and younger volcanic areas. In December 1972, after descending to the Moon, Apollo astronaut Eugene Cernan (Cernan, Eugene Andrew) and geologist-astronaut Harrison Schmitt deployed their lunar rover and traveled for a total of 36 km (22 miles) on three separate excursions around the valley, retrieving samples that had come downslope from the nearby highlands and collecting specimens of the variegated, titanium-rich mare basalt rocks and soils filling the valley. They also collected samples of orange and black glass indicative of ancient volcanic “fire fountains” (eruptive gouts of lava) on the Moon. Sample analyses conducted on Earth interpreted the highland rocks as parts of the material excavated by the enormous impact that created the Serenitatis Basin. Some rocks from the Taurus-Littrow site, which is crossed by one of the rays of material ejected from the impact that formed the comparatively young crater Tycho, suggested an age for the crater of about 100 million years. The complex geologic history of the Taurus-Littrow region makes it a prime target for future scientific landing and roving missions on the Moon.