Japan's space agency said Thursday it will postpone space probe Hayabusa2's touchdown on the Ryugu asteroid to around late January from October due to the difficulty in finding a good landing site.

The Japan Aerospace Exploration Agency said surfaces of the asteroid, about 300 million kilometers from Earth, are rougher than initially thought, and more time is needed to ensure the precise control of the probe.

[Image supplied by JAXA]

Hayabusa2 will conduct two landing rehearsals this month, JAXA said.

The agency will not be able to communicate with the probe in November and December when it will be on the other side of the sun from Earth.

Ryugu, with an estimated diameter of about 900 meters, travels around the Sun once every 16 months, passing near the orbits of Earth and Mars.

Hayabusa2, launched from the Tanegashima Space Center in southwestern Japan in December 2014, is to make multiple landings to collect rock samples, which the agency says may provide new insights into the origin of life.

The probe is now programmed to keep a distance of 20 kilometers from the asteroid. It has approached Ryugu six times since its arrival in late June to collect and analyze data for landing.

Two rovers released from Hayabusa2 successfully landed on the surface of Ryugu in late September. A different explorer developed by the German and French space agencies and carried by Hayabusa2 also landed successfully earlier in the month.