Fig. 8: Hydrothermal history of Ryugu’s parent body.

(Left) The parent body might consist of similar water/rock ratio to CM chondrites, but accreted with earlier timing, 2–2.5 Ma after CAI, to achieve the thermal metamorphism. (Middle) After pervasive aqueous alteration to form a CM-like precursor which included large amounts of Fe-bearing phyllosilicates, the parent body was dehydrated at 570–670 K (300–400 °C) due to heating by radioactive decay of short-lived radionuclides (e.g., ²⁶Al). (Right) Ultimately, Ryugu’s parent body consisted of several layers with different degrees of thermal metamorphism. Different evidence were discovered in the previous studies^5,15,41,56.