On November 13, Japan's groundbreaking asteroid explorer Hayabusa-2 will begin its journey back to Earth leaving its mission target, asteroid Ryugu, behind. After a year and a half surveying the asteroid, it will break free of its weak gravitational pull by November 18, and next month will use its thrusters to push itself on its homecoming trajectory.
The spacecraft took 3.5 years to get to asteroid Ryugu, but given the relative positions of the space rock and Earth, the return journey is expected to be much shorter. Hayabusa-2 will fly by Earth in December 2020 and deliver its precious cargo – the first-ever samples of sub-surface material from an asteroid – dropping them somewhere in the south Australian desert.
In its 17 months around the asteroid, the craft successfully delivered the first-ever rovers to land on an asteroid, which sent back the first-ever images taken on the surface of an asteroid, as well as taking detailed analysis of the celestial body and collecting three soil samples: two from the surface and one from deeper in the ground. The craft had to shoot a 2.5-kilogram (5.5-pound) bullet into the rock to expose sub-surface debris, collecting the first sample of material from beneath the soil of an asteroid.
Though Hayabusa-2's mission has come to an end, it will not stop providing exciting data just yet.
“We expect Hayabusa-2 will provide new scientific knowledge to us,” project manager Yuichi Tsuda said in a press conference as reported in AFP. “I'm feeling half-sad, half-determined to do our best to get the probe home. Ryugu has been at the heart of our everyday life for the past year and a half.”
The mission, which has lasted six years so far, has far exceeded expectations – and that’s even before the three samples are analyzed back on Earth. We have many more years of scientific data on Ryugu waiting for us.
Though the craft's mission is due to end at the end of next year when it gets close enough to Earth to drop off its samples, it may not be the end for Hayabusa-2. The probe will still have plenty of fuel, and the team at JAXA, Japan's Aerospace Exploration Agency, is currently investigating what might come next.
It is possible that the spacecraft will be sent back further into deep space to investigate another asteroid. If that happens, Hayabusa-2 will become one of the few probes to have visited multiple bodies in the Solar System.