On July 20, 1969, Apollo 11 astronauts Neil Armstrong and Edwin "Buzz" Aldrin became the first to walk on the Moon. This panorama of their landing site sweeps across the magnificent desolation of the Moon's Sea of Tranquility, with their Lunar Module, the Eagle, in the background at the far left.

Why are there so many moonquakes? A recent reanalysis of seismometers left on the moon by the Apollo moon landings has revealed a surprising number of moonquakes occurring within 30 kilometers of the surface. In fact, 28 moonquakes were detected in data recorded between 1972 and 1977.