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After visiting asteroid, Japan’s Hayabusa 2 probe heads back to Earth with samples

Alan Boyle
An image from Hayabusa 2’s camera shows the half-mile-wide, diamond-shaped asteroid known as Ryugu receding in the metaphorical rear-view mirror. (JAXA, Chiba Institute of Technology and Collaborators)

Japan’s Hayabusa 2 spacecraft and its science team bid a bittersweet farewell to the asteroid Ryugu, 180 million miles from Earth, and began the months-long return trip to Earth with a precious set of samples.

“This is an emotional moment!” the team tweeted on Tuesday.

“It’s sad to say goodbye to Ryugu,” project manager Yuichi Tsuda said at the Japan Aerospace Exploration Agency’s command center. “Literally it has been at the center of our lives over the past one and a half years.”

The farewell isn’t finished quite yet, however. Over the next few days, Hayabusa 2’s camera will capture pictures of the half-mile-wide asteroid as it recedes into the background of space. Then the probe’s field of view will turn back toward Earth for the return journey.

Hayabusa 2 was launched back in 2014 and arrived at Ryugu in mid-2018. Since then, it’s been taking close-up pictures, dropping mini-probes to Ryugu’s rubble-strewn surface, and collecting samples during touch-and-go maneuvers.

The mission is meant to to shed light on the composition of carbonaceous asteroids like Ryugu, which are thought to contain the primordial stuff of the solar system.

Spectroscopic readings have already determined that Ryugu’s rocks contain traces of water-bearing minerals — a finding that could hint at the sources of our own planet’s oceans. But the biggest revelations are expected to come from studies of the samples that Hayabusa 2 is due to send down to the Australian Outback in a capsule as the main spacecraft zooms past Earth in late 2020.

The sample return operation follows up on the first Hayabusa mission, which dropped off tiny flecks of another asteroid called Itokawa in 2010 after a glitch-plagued journey. Scientists are hoping that Hayabusa 2’s more ample samples will provide fresh insights into the development of life on Earth. To emphasize the point, they redesigned the mission’s logo with an Earth-centric theme:

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