Since arriving at the asteroid in June of this year, the probe has studied 54,000 spots on its surface. Among the data the spacecraft returned are close up images of surface boulders and ridges.
Ryugu is classed as a C-type asteroid, a category of asteroids that contain high levels of carbon and often have moisture in the boulders on their surfaces. Scientists would like to find evidence of such moisture on Ryugu, as the presence of water could make the asteroid habitable for microbial life.
Located 186.4 million miles (300 million km) from Earth, Ryugu, which rotates on its axis once every 7.5 hours and takes 474 days to orbit the Sun, is too small and distant for observers on Earth to see its surface details.
Mission scientists are not giving up on the possibility that evidence of water might still be found on Ryugu. The probe will continue studying the near-Earth asteroid for a year and a half, during which time it will drop four small rovers on Ryugu’s surface.
After identifying an ideal landing site, the spacecraft will touch down on the surface this fall, then create a hole in that surface for sample collection by firing a metal fragment into it.
Hayabusa2 is a sample return mission, meaning the probe will collect samples from the asteroid’s surface and subsurface and return them to Earth for analysis. It will leave Ryugu in December 2019 and arrive back on Earth with the samples a year later.
“There is a possibility that water might be discovered after an artificial crater is created on its surface next spring,” said JAXA project member Kohei Kitazato, a professor of Earth and planetary science astronomy at the University of Aizu.
Even if no evidence of water is found on Ryugu, that does not mean it never had water. It is possible that surface water once was present but subsequently evaporated, possibly through interaction with light from the Sun.