SpaceX's unmanned Dragon spacecraft has left the International Space Station and returned to Earth after a month in orbit.

Astronauts at the orbiting lab manipulated the space station's robotic arm to detach the Dragon on time, just before 1am today (AEDT) and it splashed down five and a half hours later in the Pacific Ocean near the Mexican coast.

The unmanned craft, which has been docked in orbit since September 23, ferried home almost 15-hundred kilos of materials, including results from experiments conducted on the space station.

The SpaceX vessel is the only spacecraft currently capable of returning with cargo.