Japan’s Hayabusa2 successfully completed its second touchdown on the asteroid Ryugu and probably captured material from its interior that was exposed by firing a projectile into the asteroid earlier this year. It is the first collection of subsurface materials from a solar system body other than the moon.
Engineers and technicians in the spacecraft’s control room near Tokyo could be seen erupting into cheers and applause on a YouTube live stream when Project Manager Yuichi Tsuda proclaimed the operation a success just before 11 a.m. local time.
At an afternoon press briefing, Tsuda said, “Everything went perfectly.” He joked that if a score of 100 indicated perfection, “I would give this a score of 1000.”
Hayabusa2 was launched by the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science in Sagamihara, near Tokyo, in December 2014 and reached Ryugu in June 2018.
Since then it has conducted remote observations, released several rovers that hopped around on the asteroid, and made a February touchdown to retrieve surface samples. To get interior material, Hayabusa2 in April released a tiny spacecraft that exploded and sent a nonexplosive, 2-kilogram copper projectile into Ryugu, creating a crater. Subsequent remote examination of the site indicated material ejected from the crater had accumulated about 20 meters to one side.
That area became the target for the second touchdown, which occurred this morning. Engineers moved the spacecraft into position above the target site over the previous day and then placed it into autonomous mode. As the craft touched down, it fired a tantalum bullet into the surface, likely kicking dust and rock fragments into a collection horn. The craft then ascended.
The team won’t know for certain what is in the sample return capsule until it returns to Earth in December 2020. “But we expect that we obtained some subsurface samples,” said project scientist Seiichiro Watanabe, a planetary scientist at Nagoya University in Japan. They will be able to compare these subsurface samples with those collected from the surface. The team believes comparing the surface samples subjected to eons of space weathering and the more pristine material from the interior will provide clues to the origins and evolution of the solar system.
Watanabe noted that NASA’s in-progress Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer mission also plans to bring samples from an asteroid, named Bennu, back to Earth in 2023. But at least for the near future, Japan is the only nation that will have acquired samples from both the surface and interior of an asteroid, Watanabe said. The samples “will have great significance scientifically,” he said.
Hayabusa2 will continue remote observations until December 2020. “We shouldn’t waste even a single day,” Tsuda said.