Samples retrieved from asteroid Ryugu indicate that it once had flowing water in far greater volumes than previously thought possible, suggesting that similar objects may have played a role in delivering vast quantities of water to Earth
By James Woodford
10 September 2025
The asteroid Ryugu, photographed by the Hayabusa 2 spacecraft
JAXA Hayabusa 2
Large quantities of water once flowed through the asteroid Ryugu, an indication that asteroids could have brought much more water to Earth than previously thought.
The origin of Earth’s water is somewhat mysterious. Incoming asteroids have been proposed as a possible source, but there are doubts about whether there have been enough impacts to bring all the water on the planet today.
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Carbonaceous asteroids like Ryugu form from dust and ice in the outer solar system. In 2019, Japan’s Hayabusa 2 spacecraft landed on Ryugu and collected 5.4 grams of material that was brought back to Earth in 2020.
Early photos of Ryugu indicated that it was far drier than expected, but more recent work found that the object was riddled with cracks that once could have been filled with crucial ingredients for life, including water.
Initial dating of the samples suggested that the asteroid was one of the oldest objects in the solar system, possibly dating as far back as its formation 4.6 billion years ago.