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Japan's Hayabusa2 probe lands successfully on asteroid Ryugu

(Mainichi)

TOKYO -- Japan's space probe Hayabusa2 successfully landed on the asteroid Ryugu on the morning of Feb. 22, the Japan Aerospace Exploration Agency (JAXA) said.

"We deemed that the space probe Hayabusa2 landed on the asteroid Ryugu at around 7:29 a.m.," the space agency announced.

JAXA succeeded in the extremely difficult task of guiding the spacecraft to a circle with a radius of just 3 meters on the celestial object, located approximately 340 million kilometers away from Earth.

JAXA officials said it was a "perfect" landing as everything progressed precisely as planned. A command to fire a projectile into the asteroid's surface to dislodge material for a sample was issued, and officials said the spacecraft highly likely has collected fragments of rocks from the asteroid.

"Everything moved ahead smoothly as we planned. In our first landing, we were able to precisely maneuver the spacecraft. I think some kind of samples have been collected," said Takashi Kubota, senior researcher at the JAXA's Institute of Space and Astronautical Science.

This is Japan's second probe that successfully landed on an asteroid following the first Hayabusa probe, which landed on another asteroid, Itokawa, in 2005.

Takashi Kubota, right, senior researcher at the JAXA Institute of Space and Astronautical Science, explains the details of the landing of the space probe Hayabusa2 on the asteroid Ryugu as mission manager Makoto Yoshikawa listens at a news conference in Chuo Ward, Sagamihara, Kanagawa Prefecture, on Feb. 22, 2019. (Mainichi/Etsuko Nagayama)

Ryugu is an asteroid measuring approximately 900 meters in diameter. The path of its orbit lies between Earth and Mars.

In the landing on Feb. 22, Hayabusa2 landed near the asteroid's equator. The area is believed to be rich in water and organic substances. Therefore, if rock samples are collected and brought back to Earth, it is expected to be a clue to helping clarify how the solar system was formed and how life came about on Earth.

In its collection of rocks, Hayabusa2 will launch metal objects into the surface of the asteroid at a high speed to create a crater. This will expose samples beneath the ground that have not deteriorated. The probe is expected to return to Earth with these samples.

It had been previously believed that there was a 100-meter-square sandy area on Ryugu suitable for the probe's landing, but it turned out that the asteroid was rocky. Fears emerged that if Hayabusa2 landed on an area with rocks standing as tall as 60 centimeters, it could damage the spacecraft. This prompted JAXA to postpone a landing scheduled for October last year and review the planned landing location and how the probe would touch down.

At around 1:15 p.m. on Feb. 21, Hayabusa2 began to descend from an altitude of 20 kilometers from the surface of the asteroid. It slowed down at an altitude of 5 kilometers to approach the asteroid's surface. The probe detected the target marker, which had been shot onto the asteroid in October 2018, when it was at an altitude of 45 meters, and descended further to an altitude of 8.5 meters. Since the target marker was about 4 meters away from the circle, controllers carefully maneuvered the probe while viewing the marker to the side.

Makoto Yoshikawa, left, Hayabusa2 mission manager at the JAXA Institute of Space and Astronautical Science, shakes hands with Takashi Kubota, senior researcher at the institute, in Chuo Ward, Sagamihara, Kanagawa Prefecture, on Feb. 22, 2019. (Mainichi/Naoki Watanabe)

JAXA confirmed at around 7:48 a.m. that Hayabusa2 had begun to ascend, judging from changes in the radio waves from the probe. Staffers noted that the speed of the ascent was just as planned, which meant the probe had not aborted the landing.

At around 8:05 a.m., the control center began to receive detailed data from Hayabusa2, based on which the JAXA confirmed that an order to shoot a projectile into the asteroid surface to collect its sample material had been issued at about 8:09 a.m. as planned.

This landing maneuver Hayabusa2 undertook is called a "pinpoint touchdown," which requires extremely precise control of the spacecraft. JAXA has been asked by the U.S. National Aeronautics and Space Administration (NASA), which is also exploring asteroids, to teach it how to land a spacecraft inside such a small circle, according to those close to Japan's space agency.

Hayabusa2 weighs about 600 kilograms. It was launched from the Tanegashima Space Center in the southern Japan prefecture of Kagoshima in December 2014.

The asteroid Ryugu is seen in this photo taken by the space probe Hayabusa2 as it was descending to its surface. (Photo courtesy of JAXA)

Hayabusa2's predecessor Hayabusa, which landed on the asteroid Itokawa in 2005, failed to shoot a projectile into the asteroid's surface, but managed to collect substances from the surface that were stirred up by the impact of the landing. Hayabusa returned to Earth in 2010.

(Japanese original by Etsuko Nagayama, Opinion Group; and Tomohiro Ikeda, Science & Environment News Department)

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