A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample

Abstract

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of ~30 °C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition.

A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu

“…The exceptionally low abundance of npFe 0 in Ryugu grains is in stark contrast to lunar and Itokawa surface samples, which contain abundant npFe 0 in both radiation-damaged layers on ferromagnesian consistent with other recent studies [27][28][29][30][31] . Therefore, to understand the space weathering of Ryugu grains is to understand the weathering of the most chemically primitive Solar System material.…”

Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System

“…More importantly, the unfractionated chemical compositions and volatile element-rich nature of CI chondrites and Ryugu support the view that they formed beyond the snow line, mostly from material that experienced minimal thermal processing. The heavy hydrogen and nitrogen isotopic compositions of Ryugu are also consistent with an outer Solar System origin (34). The findings that CI chondrites and Ryugu share the same nucleosynthetic heritage (Fig.…”

“…The findings that CI chondrites and Ryugu share the same nucleosynthetic heritage (Fig. 3) and have close mineralogical, chemical, and isotopic characteristics ( 6 , 34 ), therefore, suggest that these objects formed contemporaneously and were co-located in the same outer Solar System reservoir. It is even possible, although not required by the data, that CI chondrites and the NEO Ryugu originally derived from the same precursor object, which was fragmented by collision during its residence in the inner Main Belt ( 4 , 35 ).…”

“…A common source region for the parent bodies of CI chondrites/Ryugu and Oort cloud comets would need to be reconciled with their present-day distinct chemical and physical characteristics ( 6 , 34 , 46 ). Deuterium/hydrogen (D/H) ratios of water in carbonaceous chondrites ( 47 ) and Ryugu ( 34 ) are lower than those of Oort cloud comets and overlap partially with Jupiter-family comets ( 48 ). Simulations of ice transport in the nebula predict a spatially and temporally complex evolution of water D/H ratio in the nebula ( 49 ).…”

Near-superhydrophobic silicone microcapsule arrays encapsulating ionic liquid electrolytes for micro-power storage assuming use in seawater

“…In astronomy, in the asteroid Ryugu’s returned sample, it was found that an aliphatic carbon-rich organic matter was concentrated in coarse-grained hydrous silicate minerals. This means that the coarse-grained hydrous silicate minerals as a shell wall became cradles of organic matter and water and were transported to earth intact 15 . For energy application, phase change materials have been enclosed in various shell walls for thermal energy storage 16 – 20 .…”