Our Earth is not the only rocky planet in the Solar System . But it still has a characteristic that the others do not have: it is covered with water to more than 70%! And researchers have long questioned its origin.
Today, a team led by the University of Glasgow (Scotland) suggests that the solar wind , composed in particular of hydrogen ions , could have created, on the surface of tiny grains of dust, water then deposited on Earth by asteroids which would have crossed the trajectory of our Planet at the beginning of the history of our Solar System.
Let us recall that one of the hypotheses to explain the presence of water on Earth involves collisions with type C asteroids – carbonaceous asteroids, like 75% of asteroids – in the last phases of formation of our Planet. But the isotopic footprint of these objects does not quite match. Another source seems necessary.
Water for space missions
So the researchers turned to an S-type asteroid – asteroids mostly made up of silicates. And they carried out an in-depth analysis of the few grams of dust from the Itokawa asteroid brought back to Earth in 2010. Thanks to an atomic tomographic probe, which allows the spatial distribution of the atoms in a sample to be observed in high resolution , scientists have indeed had access to the first 50 nanometers of the surface of these dust grains. They would contain the equivalent of 20 liters of water per cubic meter. Water isotopically lighter than that which could have arrived on Earth on the backs of type C asteroids. The trail looks good.
The researchers also hope that their work will be useful for future space missions . Because they show that the same weathering process that created water on Itokawa probably occurred on planets devoid of atmosphere. So astronauts might be able to collect cool water directly from dust on the surface of the Moon , for example.