Ryugu Samples Reveal Late Flowing Water That Upends Asteroid Water Models

Overview

• Using Hayabusa2-returned material, a Nature study finds evidence that liquid water flowed on Ryugu more than a billion years after formation.
• Measurements of lutetium‑176 and hafnium‑176 show unexpectedly high Hf/Lu ratios consistent with late fluid disturbance of the Lu–Hf clock.
• The team infers an impact on a larger parent asteroid heated and melted buried ice, driving water through fractures.
• The finding suggests some asteroids were significantly wetter than assumed, potentially by a factor of two to three.
• Researchers will compare the Ryugu signal with OSIRIS‑REx Bennu samples to validate the mechanism and timing.