Between June 20th and 23rd, 2021 “Team Kochi” [note 1], led by senior researcher Dr Motoo Ito [note 2], undertook cutting edge imaging analysis of samples returned to Earth from Asteroid Ryugu [note 3] by the JAXA Hayabusa2 spacecraft [note 4]. This marked the start of an intensive analytical campaign involving researchers from a wide range of institutions, both in Japan and internationally [note 5], including the Open University in the UK and UCLA in the US.
The samples being analyzed by “Team Kochi” were collected by the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 spacecraft from the surface of the “primitive” asteroid: Ryugu. Hayabusa2 was launched in December 2014, arrived at asteroid Ryugu in 2018 and then commenced one of the most successful asteroid exploration missions of all time. This involved a detailed survey of the asteroid using onboard instruments. Samples from the surface of asteroid Ryugu (approximate mass 5.4 g) were collected by the Hayabusa2 spacecraft and then successfully delivered to Earth on December 6th 2020.
The analysis performed by “Team Kochi” on June 20–23, 2021 involved the use of the SPring-8 synchrotron facility [note 6] to undertake computed tomography (CT) analysis [note 7]. This allowed the team to obtain extremely detailed three-dimensional images of the Ryugu samples. The exact technique that was used has been specifically developed for Ryugu samples, as they contain hydrous mineral phases and organic matter with a complex microstructure. An ultra-high-resolution 3D visualization technique (integrated CT technique (XRD-CT, CT, nano-CT, and Phase-contrast CT)) [note 7][note 8] will be performed later this year at SPring-8 to obtain the distribution of organic matter in the Ryugu samples.
The images and data obtained at SPring-8 will be of assistance to the other members of “Team Kochi” in their studies of these exceptionally important extraterrestrial samples. “Team Kochi” will be applying a wide range of compositional and isotopic measurement techniques to learn as much as possible about the formation and evolution of the Ryugu grains. [note 9]
The oxygen isotope work to be performed at the Open University in the UK will provide critical information about the origin and early history of this material and will tell us how it relates to other extraterrestrial samples, such as meteorites. Material from asteroids similar to Ryugu may have brought water and organic matter to early Earth, thus making it a more habitable planet.
High-spatial resolution and high-precision isotope microanalysis work will be performed at the UCLA SIMS lab in the US. Stable isotope analysis, in combination with a chronological study of particular minerals, will provide constraints on the exchange processes between water and minerals and the timing of aqueous alteration within a carbonaceous asteroid. This information is critical in deciphering the earliest history of water-mineral phase reactions inside a planetesimal.
Scientific analysis undertaken by research institutes in Japan, UK and US as part of “Team Kochi” will not only help to constrain the history of organic matter and water on Ryugu, but may also help us to understand the early evolution of Earth.
Asteroid Ryugu – (image: JAXA)