A team of scientists has uncovered a potential new mechanism for bringing water to Earth, offering a promising outlook on previous theories.
Based on numerous observations of the Solar System, as well as others made at the ALMA radio telescope, of extrasolar debris disks, the study appeared in the journal Astronomy and Astrophysics on December 3, 2024.
Water is an essential element for life on Earth; However, scientists believe that the young Earth lacked them when it formed. Located too close to the Sun, our planet would have been too hot to retain water at its origin. Current theories therefore suggest an influx of water from outside, occurring during the first 100 million years of terrestrial history. Until now, the dominant theory assumed that icy bodies, similar to comets, had struck the Earth, bringing the water. However, this scenario requires a cosmic “game of billiards”, where complex dynamic mechanisms send these icy objects towards Earth, at a precise time and in sufficient quantity. Random to say the least, this scenario is questioned as to its robustness, and its universality across all extrasolar systems.
Based on precise data from isotopic measurements carried out in the Earth’s atmosphere, as well asobservations recent asteroids (including the results of space missions that have come close to asteroids like Hayabusa 2 and OSIRIS-REx), a new model of the evolution of the asteroid belt was able to be set up and then tested on the data terrestrial.
In addition, observations of extrasolar disks, related to our asteroid belt, were carried out using the ALMA radio telescope, to test the universality of this new water supply mechanism; this could potentially be successfully applied to a variety of extrasolar systems.
The new study proposes an alternative, less random mechanism
If, as we think today, asteroids were formed, frozen, in a disk primordial cold, then with the disappearance of this young disk, the asteroids, warming up, gradually released their ice in the form of water vapor. This water vapor then formed a new disk composed mainly of water surrounding the asteroid belt and orbiting the Sun.
This steam bath, spreading little by little in the internal Solar System, ends up enveloping the planets which capture part of it for the benefit of the formation of the oceans, between 10 and 100 million years later. © Sylvain Cnudde/Paris Observatory – PSL/LESIA
Under the effect of dynamic forces, this disk of water vapor gradually spread out, eventually reaching the inner planets of the Solar System, including Earth. When they found themselves in this bath of water vapor, the planets were able to capture part of it, thus contributing to the formation of the oceans.
This mechanism also helps explain the presence of water on other planets in the Solar System. Likely to have a universal scope, it offers a promising avenue for identifying exoplanets capable of harboring water and, potentially, life.
References:
Quentin Kral et al, “An impact-free mechanism to deliver water to terrestrial planets and exoplanets”, A&A, 3 décembre 2024.
