Dr Luke Dalys and colleagues believe that the solar wind, made up of charged particles, largely made up of hydrogen ions, created water on the surface of dust grains which reached the surface in large quantities. of early Earth at the same time the asteroids were also crashing there.
On the origin of water
One of the most accepted theories to explain the presence of water on Earth is the intensive bombardment of its surface by C-type asteroids during the later stages of its formation.
To test this hypothesis, the researchers analyzed the
footprint isotopic of pieces of those asteroids that took the form of water-rich carbonaceous chondrite meteorites once reached the earth’s surface.
If the ratio of hydrogen to deuterium found in the water of these meteorites matches that of terrestrial water, we could conclude that type C meteorites are the likely source., explain the researchers in a press release.
But the results obtained are not so clear.
On average, the liquid footprints of these meteorites do not match the water in the Earth’s mantle and oceans. On the contrary, the planet has a different isotope footprint, a little lighter, explains the University press release.
In other words, while some of the Earth’s water has certainly arrived via asteroids, another source
isotopically lighter from somewhere else in the solar system must also have contributed.
The team used a unique analytical process, called atomic probe tomography, to scrutinize samples from another type of space rock, S-type asteroids, which orbit closer to the Sun than C-type asteroids.
The samples analyzed come from the asteroid Itokawa. They were collected by the Japanese probe Hayabusa and brought back to Earth in 2010.
Atomic probe tomography enabled the team to measure the atomic structure of grains, atom by atom, and detect individual water molecules, explain the researchers.
Their results show that a significant amount of water was produced below the surface of the Itokawa dust grains.
As the solar system in formation is very dusty, scientists believe that it therefore offered many possibilities for the production of water below the surface of the dust particles.
This water-rich dust would have rained abundantly on the primitive Earth, at the same time as the fall of type C asteroids, two phenomena which would have led to the formation of the oceans., concludes Luke Dalys.
Details of this work are published in the journal Nature Astronomy (New window) (in English).
In August 2020, the French cosmochemist Laurette Piani and her colleagues put forward the hypothesis that the Earth would have been, from its origin, rich in water, probably contained in abundance in the rocks that made it up.