TOKYO, Japan (Reuters) -- A Japanese space probe on a mission to bring back the first rock samples from an asteroid is preparing to make a fresh attempt to land on its target, Japan Aerospace Exploration Agency (JAXA) officials said on Friday.The officials said they plan to land the unmanned probe on the asteroid, nearly 300 million kilometers (200 million miles) from earth, shortly after 7 a.m. on Saturday (2200 GMT on Friday)."It is moving closer and closer to the asteroid. It is about 20 kilometers (12 miles) from the target site now," a JAXA official said on Friday morning.He said the probe would begin its final approach around 10 p.m. (1300 GMT) on Friday.After a voyage of 2 1/2 years, the space probe on Sunday touched down on the surface of the 548-meter-long asteroid, called Itokawa, marking the first landing by a Japanese spacecraft on an extraterrestrial body. It remained there for 30 minutes but failed to drop the equipment for collecting surface material.Asteroids, unlike larger objects such as the moon, are believed to contain rocks that have remained largely unchanged since the early days of the solar system and could thus offer valuable information about its origins.Information about their structure could also be vital if an asteroid were found to be on a collision course with the earth.The probe, called Hayabusa (Japanese for "falcon"), has already sent back detailed images of the asteroid, which Japanese media noted looks like a potato.In a photograph published on JAXA Web site, the probe's shadow can be made out on Itokawa's surface.Itokawa is named after pioneering Japanese rocket scientist Hideo Itokawa.Copyright 2005 Reuters. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.