TOKYO, Feb. 21 (Xinhua) -- Japan's space probe Hayabusa2 began its descent Thursday to an asteroid named Ryugu, which the probe arrived above in June last year, the space agency here said.
According to the Japan Aerospace Exploration Agency (JAXA), the probe began its descent to the asteroid from an altitude of 20,000 meters above at about 0400 GMT, with the descent being delayed for a few hours while the final approach to the asteroid's surface was rechecked.
The probe is scheduled to touchdown on the asteroid on Friday morning and begin collecting rock samples from Ryugu's surface, JAXA said, adding that if any abnormalities were detected in the landing procedure, the mission would be immediately aborted.
The initial touchdown on the asteroid was postponed in October last year as JAXA found the surface of the asteroid, which is about 300 million km from the Earth and 900 meters in diameter, to be rockier than it first thought and needed more time to ensure the safe landing of the probe.
On Oct. 3, 2018, Hayabusa2 released a small-sized Mobile Asteroid Surface Scout, also known as MASCOT, jointly developed by the German and French space agencies, which touched down successfully on the asteroid.
Prior to that, two small robotic rovers also launched from Hayabusa2 successfully landed on Ryugu on Sept. 22.
The rovers have been taking images of the asteroid and performing other functions such as measuring its surface temperature.
JAXA said the images of Ryugu captured by the robots have revealed a cluster of bumpy rocks and a lack of flat surfaces for the main probe to land on.
The agency has since located a flat area near Ryugu's equator that is free of rocks larger than 60 centimeters, it said.
The scientists are aiming to land the probe on a far smaller landing area than originally planned that is now just 6 meters in diameter.
The 600-kg Hayabusa2, which was launched from the Tanegashima Space Center in southwestern Japan in December 2014, has experienced no problems up until now, throughout its journey totaling 3.2 billion km.
The agency said in total, Hayabusa2 is scheduled to make three landings on the asteroid and collect rock samples and will stay close to Ryugu for one and a half years.
During this time it will conduct a number of exploratory activities in an attempt to try to find clues about the solar system's evolution and the beginning of life itself.
Hayabusa2's mission will be completed when it returns to the Earth in 2020 with the samples of rocks it has collected from Ryugu, which is thought to contain water and other materials that could possibly support life.
