Looking at the night sky often raises big questions. Could ancient asteroids have carried water that shaped our planet? Scientists in Japan now think so, after finding new evidence inside asteroid Ryugu.
Did Liquid Water Once Flow in Ryugu?
Researchers studied samples returned by Japan’s Hayabusa2 mission in 2020. The spacecraft visited the near-Earth asteroid between 2018 and 2019. It landed a probe on the spinning top-shaped rock and collected material. Scientists now report chemical signatures suggesting water once flowed through Ryugu.
The study, published on 10 September in Nature, shows unusual isotopes in the samples. Researchers examined lutetium-176 and hafnium-176 ratios, using the known half-life of lutetium. Instead of expected levels, they found too much hafnium-176. The team believes ancient liquid water washed away much of the lutetium. This process may have begun soon after the asteroid was formed.
Lead author Tsuyoshi Iizuka of the University of Tokyo called the findings a surprise. He said Ryugu preserved a clear record of past water activity. There is evidence fluids once moved through its rocks.
What Triggered Water Flow Inside Ryugu?
The researchers believe an impact on a larger parent body triggered the process. Such a collision may have fractured the asteroid and melted buried ice. This would have allowed water to move through the rocky interior.
The James Webb Space Telescope earlier suggested Ryugu and Bennu may share a parent. However, Bennu samples studied so far show no signs of flowing water. That leaves questions about their true origins.
Ryugu’s watery history suggests its parent body could have kept ice for at least a billion years. This is longer than most asteroids were thought capable of retaining water.
Could Asteroids Have Delivered More Water to Earth?
The findings also raise questions about Earth’s water supply. Scientists widely accept that water came from impacts by asteroids and comets. The new study suggests asteroids could have delivered up to three times more water than previously believed.
Iizuka said this discovery changes how scientists view the fate of water in asteroids. The water remained much longer than expected and was not quickly lost.
The research team now plans further analysis of phosphate veins within the samples. This could give a clearer age for the water. They also hope to compare isotopes from Bennu to see if it too had liquid water in its past.
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