학술논문

Insight into multi-step geological evolution of C-type asteroids from Ryugu particles
Document Type
Original Paper
Source
Nature Astronomy. 7(4):398-405
Subject
Language
English
ISSN
2397-3366
Abstract
C-type asteroids are the source of the carbonaceous chondrite meteorites and represent remnants of primitive planetesimals that formed at the outer margins of the early Solar System and may have delivered volatiles to the inner Solar System, in particular the early Earth. However, the nature of carbonaceous chondrites is not well understood owing to terrestrial alteration. Here, we present the petrology and mineral chemistry of surface materials collected by the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 spacecraft from the C-type asteroid Ryugu. The Ryugu particles we studied are similar to CI (Ivuna-type) chondrites but with some important differences, such as the presence of Na–Mg phosphates and Na-rich phases and the lack of ferrihydrite and gypsum. Ryugu particles experienced several steps of aqueous alteration, metasomatism and brecciation under variable conditions. These materials represent mixed lithologies and formed at different locations within their parent asteroid. The evidence presented here demonstrates that the C-type asteroid Ryugu experienced a complex geologic evolution shortly after its formation.
The returned samples from Hayabusa2 show that C-type asteroid Ryugu experienced various steps of mineralogical alteration within only 1–2 million years after accretion.