Astrophysicists propose a novel theory regarding the origin of Earth's water, suggesting it may have been captured from vapor disks around asteroids shortly after the formation of the Solar System. This study, led by Quentin Kral from the LESIA laboratory at the Paris-Meudon Observatory, was published in Astronomy & Astrophysics on December 5, 2024.
Traditionally, it is believed that water arrived on Earth primarily via asteroids and comets from outside the Solar System during its first hundred million years. Kral's model suggests a more straightforward mechanism, potentially applicable to other rocky planets like Mars and Mercury, which are known to contain water.
The research focuses on the asteroid belt, which lies between Mars and Jupiter and was significantly more massive during the early Solar System, approximately 4.6 billion years ago. Kral states that these asteroids were initially icy, with remnants detectable in hydrated minerals found on other asteroids, such as those sampled from the asteroid Ryugu by a recent Japanese mission.
In Kral's scenario, the Sun's formation heated the asteroid belt, peaking around 25 million years ago. This heating sublimated the ice, creating a vapor disk that spread throughout the Solar System. As the Earth cooled, it gradually captured this vapor, which eventually condensed into liquid water.
This hypothesis marks the first of its kind and is informed by observations from the ALMA radio telescope, known for detecting gas and dust clouds in the universe. Kral notes that for a decade, scientists have identified carbon and oxygen gas disks in planetesimal belts, indicating a shift from merely detecting cosmic dust.
The team plans to further test their theory by observing slightly younger stellar systems that still possess their water vapor disks, hoping to gather new insights into the processes that may have contributed to the formation of water on Earth.