Asteroid Ryugu once had liquid water flowing through it

Recent analyses indicate that extensive volumes of water once flowed through asteroid Ryugu, leading scientists to reconsider the role of similar celestial bodies in supplying water to Earth.

The origin of Earth’s water remains one of science’s greatest mysteries. Asteroid impacts have been theorized as a primary source, yet questions linger about whether they could account for the planet’s current water volume.

Ryugu is categorized as a carbonaceous asteroid, a type that originates from dust and ice in the outer solar system. In 2019, Japan’s Hayabusa 2 mission successfully collected 5.4 grams of samples from Ryugu, which were returned to Earth in 2020.

Initial observations labeled Ryugu as surprisingly dry, but subsequent research unveiled expansive cracks that could have been filled with vital ingredients for life, including liquid water.

The samples have been dated to possibly be among the oldest objects in our solar system, likely originating around 4.6 billion years ago.

However, Tsuyoshi Iizuka from the University of Tokyo and his research team discovered that their dating of Ryugu’s materials suggested ages exceeding that of the solar system. “Our analysis returned ages around 4.8 billion years, which exceeds the expected age of the solar system,” Iizuka noted.

This suggests that at some point, approximately one billion years after Ryugu’s parent body formed, it experienced warming sufficient to convert ice into liquid water, thus modifying the original lutetium-176 concentration used for dating.

Because solar radiation can only penetrate up to 40 centimeters into the asteroid’s surface, the discovery implies that a collision with another object may have heated the interior, allowing water to flow.

Estimations of the water volume reveal that Ryugu contained roughly 20 to 30 percent water—significantly more than earlier calculations. Iizuka suggests that rather than simply delivering water as minerals, asteroids like Ryugu may have also provided water in liquid form.

The implications of this research extend to understanding how planetary bodies acquired their water. Jonti Horner from the University of Southern Queensland, who was not involved with the study, emphasizes the importance of sample return missions in building confidence in the results, stating, “Having directly obtained samples allows for a clearer narrative, enhancing our assurance regarding these water-rich asteroids’ potential contributions to Earth’s early ocean.”

As research continues to unfold, these findings paint a clearer picture of how similar celestial objects may have been fundamental in shaping the earliest environment of our planet.