Japanese probe images asteroid Ryugu

Impactor will create crater from which samples will be collected and sent back to Earth for analysis.
By Laurel Kornfeld | Oct 01, 2018
Just days away from its target, asteroid Ryugu, Japan's Hayabusa2 spacecraft has captured the most detailed photos yet of the 3,000-foot-wide (900-meter) rocky object.

Launched in 2014, Hayabusa2 is scheduled to arrive at its destination on June 27 and enter orbit around it next month. The spacecraft will deploy three rovers and a lander on Ryugu's surface and collect samples that will be returned to Earth for analysis.

Ryugu will be drop the rovers and lander from a height of 12.5 miles (20 km) between September of this year and July 2019.

Hayabusa2 will also release an impactor to hit the asteroid, creating a crater from which samples will be collected and returned to Earth in 2020.

Close-up images show that Ryugu, which rotates in the opposite direction of both the Earth and the Sun, has a surface characterized by dents, craters, and sharp angles.

Data returned by the probe indicates the asteroid has a rotation period of 7.5 hours and a vertical rotation axis perpendicular to its plane of orbit.

Ryugu's shape is similar to that of another asteroid, Bennu, the target of NASA's asteroid sample return spacecraft OSIRIS-REx, which will arrive there in August of this year.

"When I saw these images, I was surprised that Ryugu is very similar in shape to both the destination of the US OSIRIS-REx mission, asteroid Bennu, and also the target of the previously proposed MarcoPolo-R mission by Europe, asteroid 2008 EV5," said Hayabusa2 mission manager Makoto Yoshikawa of the Japanese space agency JAXA.

He noted that both Bennu and 2008 EV5 are smaller than Ryugu and rotate faster than it does, yet all three have similar compositions.

"So, we have both differences and similarities that have combined to produce very similar shapes...why is that?"

To date, all the asteroids that have been explored have shapes very different from one another. Ryugu and Bennu could be the first two asteroids of similar shape to ever be visited, Yoshikawa said.

Accurate mapping of Ryugu is essential to finding the best landing locations for the rovers and lander. Mission scientists will have a better idea of their options once they have images of the whole asteroid.

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