Images from the surface of asteroid Ryugu yield clues to its composition

New images taken by a lander on the surface of the near-Earth asteroid Ryugu have yielded clues into the composition and origins of its rocks, which bear strong similarities to primitive meteorites called carbonaceous chondrites. The findings from Ralf Jaumann and colleagues present evidence linking the asteroid to a particular class of meteorites, supporting theories that Ryugu formed during a cataclysmic event.

The image shows the first acquired by the DLR-developed MASCAM camera system during Hayabusa2’s descent, shortly after separation from the landing module at a height of 41 meters with a viewing direction towards the south pole. Particularly striking is a huge block near the South Pole, which stands out clearly above the horizon line and which is named “Otohime Saxum”. It is up to 100 meters tall. Credit: Jaumann et al., Science (2019)

The Hayabusa2 spacecraft is designed to sample rocks from Ryugu and return them to Earth, which could help scientists understand the formation of the Solar System. The main Hayabusa2 spacecraft carried a lander called the Mobile Asteroid Surface Scout (MASCOT), which was dropped onto Ryugu’s surface in October 2018.

The second image of the DLR-developed MASCAM camera is directed oblique downward on the asteroid Ryugu and covers areas east of the descent route. Compared with the first image, it is clear that MASCOT moved turbulently towards Ryugu , as expect, thus performing turns and rollovers. The images show a huge boulder, which occupies the eastern edge of the image and is several tens of meters in length. Credit: Jaumann et al., Science (2019)


As the lander approached the surface, its camera took images that allowed Jaumann et al. to reconstruct the trajectory of MASCOT, which descended slowly and bounced across the surface before settling. Further images taken on the surface show the asteroid is covered with rocks and boulders that fall into one of two categories: dark and rough, or bright and smooth. Both rock types are almost evenly distributed on the surface, supporting a theory that Ryugu formed from rubble that reaccumulated after an impact onto a parent body, resulting in two types of material.

Before the first contact with a large rock on Ryugu, DLR’s MASCAM camera photographed the area of the descent route with a backward-looking view. Credit: Jaumann et al., Science (2019)


Many rocks also harbor small, colored inclusions similar to those found in carbonaceous chondrites, indicating that they may contain the mineral olivine. Unexpectedly, the images showed no fine particles or dust on the surface, which would be expected to accumulate following space weathering. The authors believe there must be an unidentified physical mechanism that efficiently removes dust from the asteroid’s surface.

Image acquired by the DLR-developed MASCAM camera system, taken at right. Credit: Jaumann et al., Science (2019)