Tokyo: Japan's Hayabusa2 spacecraft has released a small rover that will land on the surface of an asteroid as part its final mission before heading back to Earth, where it will land in the South Australian desert later this year.

The rover MINERVA-II2 is captured by the wide-angle optical navigation camera immediately after separation. Credit:JAXA

The Minerva-II2 rover began a slow descent to the asteroid Ryugu, the Japan Aerospace Exploration Agency, or JAXA, said.

Hayabusa2 arrived in the area in June 2018. It has collected soil samples and other data from the asteroid 300 million kilometres from Earth in a series of missions aimed at obtaining clues to the origin of the solar system.

The spacecraft released the rover, which resembles a circular cookie tin, from about 1 kilometre above the asteroid's surface. It will collect data and images of the rover as it descends over the next few days to Ryugu - named after a dragon castle in a Japanese folk tale - to research the asteroid's gravity.