'Great Scott' lunar rock sample. Lunar sample 15555, obtained during the Apollo 15 mission lunar surface operations (30 July to 2 August 1971), was called 'Great Scott' after NASA astronaut David Scott who collected it. The largest (9.5 kg) of the Apollo 15 rocks, it is an olivine basalt that is 3.3 billion years old. The symbol at bottom right indicates that this is the 'north' side of the rock. The Apollo moon landings returned 2,415 samples and over 380 kilograms of moon rock. Moon rocks aid studies of conditions in the early solar system when the Moon and Earth were forming. Photographed in 1971, in the Lunar Receiving Laboratory, Houston, Texas, USA.