TOKYO (AP) — A Japanese spacecraft has released two small exploration robots on an asteroid in a research effort that may provide clues to the origin of the solar system.

The Japan Space Exploration Agency said the two Minerva-II-1 rovers were lowered from the unmanned spacecraft Hayabusa2 to the asteroid Ryugu. The spacecraft arrived near the asteroid, about 280 million kilometers (170 million miles) from Earth, in June.

JAXA said confirmation of the robots' touchdown has to wait until it receives data from them on Saturday.

The two robots will capture images of the asteroid and measure temperatures before a larger rover is released in early October. The robots move by hopping because extremely weak gravity makes rolling difficult.

Hayabusa2, launched in December 2014, is due to return to Earth in late 2020.