NASA video shows dark side of the moon

NASA has released a rare video of the far side of the moon, captured by one of the two GRAIL probes that are orbiting the moon to map its gravitational field.

The US space agency published the video, which was shot on 19 January, on Thursday. The footage came from a camera that will be used by American students to study the moon's surface.

NASA's Gravity Recovery And Interior Laboratory (GRAIL) mission involves two spacecraft that are orbiting the moon in tandem, using fluctuations in the distance between them to measure changes in gravitational pull. By doing so, the probes are able to effectively map underground geological structures.

The probes, which were launched last September and went into orbit around the turn of the year, were originally called GRAIL-A and GRAIL-B. In January, US schoolchildren named them Ebb and Flow respectively.

The imagery published on Thursday came from Ebb's MoonKAM, which stands for 'Moon Knowledge Acquired by Middle school students'. Students will be able to choose parts of the lunar surface which the MoonKAMs should film. Flow's MoonKAM is yet to be tested.

The footage is rare because the far or 'dark' side of the moon is permanently turned away from the Earth.

"In the video, the north pole of the moon is visible at the top of the screen as the spacecraft flies toward the lunar south pole," NASA explained in Thursday's statement. "One of the first prominent geological features seen on the lower third of the moon is the Mare Orientale, a 560-mile-wide (900km) impact basin that straddles both the moon's near and far side."

"The clip ends with rugged terrain just short of the lunar south pole. To the left of centre, near the bottom of the screen, is the 93-mile-wide (149km) Drygalski crater with a distinctive star-shaped formation in the middle. The formation is a central peak, created many billions of years ago by a comet or asteroid impact."