Japan's Asteroid Probe Is Finally Returning To Earth With Its Precious Cargo

Artist’s conception of Hayabusa2 at Ryugu. (Image: JAXA)

The Japanese space agency has declared an end to the exploratory phase of the Hayabusa2 mission. Beginning tomorrow, the overachieving spacecraft will leave Ryugu and head back to Earth, bringing—hopefully—its asteroid samples along with it.

After a year and a half of exploratory work around the Ryugu asteroid, the time has finally come for JAXA’s Hayabusa2 spacecraft to return home.

At 10:05 a.m. tomorrow Japan time, the probe will receive its instructions to leave the Ryugu system, reports the AFP. Hayabusa2 should break free of the asteroid’s gravity on November 18, after which time it will fire its main thrusters and begin its journey toward Earth. The probe is expected to return in December 2020.

The Ryugu asteroid. (Image: JAXA)

Along for the ride will be the all-important asteroid samples. The probe managed to touch the surface twice, attempting to collect surface samples on February 21, 2019 and deeper materials on July 11, 2019.

In addition, Hayabusa2 took numerous photos of the asteroid and deployed several robotic probes to the surface, among other tasks. Looking back, the mission has been nothing short of a spectacular success—though the final sigh of relief will come when scientists open the cargo containers and confirm that they really do contain the samples of asteroid they were designed to collect.

“I’m feeling half-sad, half-determined to do our best to get the probe home,” project manager Yuichi Tsuda told reporters earlier this week, as reported by AFP. “Ryugu has been at the heart of our everyday life for the past year and a half.”

Thankfully, the year-long journey home is much shorter than the 3.5 years it took for Hayabusa2 to reach the asteroid. Earth and Ryugu are now closer together along their respective orbital paths compared to 2014, when the asteroid was nearly 300 million kilometres from Earth.

Hayabusa2 began packing for home earlier this summer when it placed the sample chamber inside its re-entry capsule. Unlike its predecessor, the Hayabusa2 spacecraft will not burn up in Earth’s atmosphere. Instead, it will jettison the samples once at Earth, where they’re expected to land in the South Australian Desert (JAXA is currently negotiating with the Aussie government to iron out some important details, including permits to retrieve the re-entry capsule in the restricted Woomera territory). As for Hayabusa2, it will stay in space, where it could be recycled for another asteroid mission.

JAXA scientists are expecting the samples to contain bits of carbon and organic compounds. By studying these samples, scientists hope to glean new insights into the composition of asteroids and how they formed some 4 billion years ago during the early days of the solar system.

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