Hydrogen abundance estimation model and application to (162173) Ryugu

Context. The JAXA asteroid sample return mission Hayabusa2 acquired a huge quantity of data from the (162173) Ryugu during its 1.5 years in proximity orbit. On December 5, 2020 (Japan time), Hayabusa brought back to Earth 5.4 g Ryugu’s surface. Aims. We analyzed near-infrared spectra Ryugu, particular band at 2.72 μm, with aim investigate hydrogen content H 2 O and OH − groups hydrated phyllosilicates on applied two different methods, normalized optical path length (NOPL) effective single-particle absorption thickness (ESPAT), 3 μm region band, we compared obtained spectral parameters those carbonaceous chondrite meteorites whose was determined laboratory. Methods. derived an exponential correlation between selected meteorite respective ESPAT NOPL parameters. average value surface relative variations, combining results is 0.52 −0.21 +0.16 wt.%. These methods can be other asteroids that exhibit estimate mean content. Results. used present small variations across do not show any evident relation geomorphological structures. Our estimation global agreement several aqueously altered chondrites measured laboratory most similar heated CM. study phyllosilicate group method may observed primitive asteroids. will allow Solar System evolution models constrained formation better understood.