Researchers have uncovered surprising evidence that the asteroid Ryugu contained liquid water much more recently than previously believed. A study using an 80-milligram sample from this near-Earth asteroid reveals that water was present within its structure, indicating significant geological activity long after its formation. This discovery challenges existing models of the early Solar System and suggests that Ryugu’s parent body maintained liquid water for an extended period without evaporating or chemically reacting with surrounding minerals.
Geochemist Tsuyoshi Iizuka from the University of Tokyo expressed his astonishment at the findings, stating, “We found that Ryugu preserved a pristine record of water activity, evidence that fluids moved through its rocks far later than we expected.” This insight into the asteroid’s history sheds light on the conditions that may have influenced the development of water on Earth.
Ryugu’s Formation and Water Activity
Ryugu was formed approximately 4.565 billion years ago as part of a planetesimal, which is considered a building block of planets. Composed of ice and dust, this protoplanet likely underwent a thaw approximately a billion years after its creation. Researchers theorize that a collision could have fractured the planetesimal, generating heat that melted buried ice and initiated the flow of liquid water.
Such events may have had profound implications for the early Solar System. If the collision expelled liquid-filled asteroids toward the inner Solar System, it could mean that similar bodies contributed significantly more water to Earth than previously estimated. This finding is particularly relevant as scientists have long grappled with the apparent scarcity of moisture in the early inner Solar System, which has implications for the theory that asteroids were responsible for delivering water to Earth’s oceans and atmosphere.
Implications for Earth’s Water Origins
The analysis of Ryugu’s chemical composition is based on the radioactive decay of lutetium-176 to hafnium-176. When liquid water is present, it disrupts the decay process, resulting in distinct isotopic ratios. The samples from Ryugu exhibited a significantly different ratio of 176Lu to 176Hf compared to Earth meteorites, indicating that the Lu-Hf system had been affected by late-stage fluid flow, as noted by Iizuka.
While Ryugu is now dry, its chemical record provides valuable insights into the conditions of the early Solar System. The findings suggest that the building blocks of Earth may have contained more water than previously thought, prompting a reevaluation of the initial conditions of our planet’s water system.
The study detailing these findings was published in the journal Nature, further adding to the growing body of evidence that asteroids like Ryugu could be pivotal in understanding the origins of water on Earth and other celestial bodies. As research continues, these discoveries may reshape our knowledge of the early Solar System and how it contributed to the development of life on Earth.
