Ryugu is a near-Earth Cg-type asteroid belonging to the Polana collisional family. Also known as 1999 JU3, the diamond-shaped object was discovered in May 1999 by astronomers with the Lincoln Near-Earth Asteroid Research. “We thought that Ryugu’s chemical record would resemble certain meteorites already studied on Earth,” Dr. Iizuka said. “The idea that Ryugu-like objects held on to ice for so long is remarkable,” Dr. Iizuka said. Late fluid flow in a primitive asteroid revealed by Lu-Hf isotopes in Ryugu.