Recently accepted and posted by Nature– yes, Nature. 10 Sep 2025:
Iizuka, T. Shibuya, T. Hayakawa, T. et al. Late fluid flow in a primitive asteroid revealed by Lu–Hf isotopes in Ryugu s41586-025-09483-0
Certain isotopes decay to known, stable, predictable levels over useful timescales, making them tracer isotopes. Iizuka et al. have done the isotope detection, assay, and balance work for samples of Ryugu. The conclusion? The aqueous fluid- water and its entrained materials- didn’t just exist on Ryugu for a brief window in the early Solar System, when everything was warmer, denser, being subject to collisions, etc. The water in Ryugu existed over geologic timescales. Water- liquid water, enough to form currents- was held by Ryugu for roughly a billion years. In turn, this implies the water of such asteroids, claim Iizuka et al., is now two or three times more likely to be delivered to the early Earth than we had thought. Asteroidal water is now more likely to be the source of Earth water, by two or three times.