How did water form on our planet? The question to which science has not yet found answers is one step away from a possible solution
In planetary science, one of the questions still very much alive within the scientific community concerns the origin of water on planet Earth. It is not yet known with certainty what allowed the formation of water on our planet, but the most recent studies seem to agree on one point: water has, at least in part, an exogenous origin. That is: it was not formed on Earth, but arrived from far away.
Did water arrive from space?
The many different studies that prove the presence of water on meteorites have long seemed to suggest the hypothesis that water arrived on Earth from deep space, making it the habitable planet we know today.
The passage of asteroids could have brought water to our planet 4.6 billion years ago, then? Not really, because the composition of the water found on the various asteroids analyzed is not exactly identical to the water in Earth's oceans, as it contains a "heavier" form of hydrogen - deuterium.
There must then be something else, in interplanetary space, capable of explaining the mysterious origin of the water in the oceans.
Thanks to the analysis of fragments of the asteroid Itokawa - brought back to Earth by the Hayabusa mission in 2010 - a team from the University of Glasgow led by Luke Daly has made a discovery that completely changes the course of future investigations.
The Itokawa asteroid shows clear evidence of irradiation by solar winds, which are capable of turning tiny grains of "stardust" into water: "for every cubic meter of material, you can have 20 liters of water," Daly claims.
The origin of the Oceans
The solar winds are powerful flows of particles from the Sun, which radiate throughout interplanetary space, forming the so-called heliosphere.
These plasma flows are composed mainly of ionized hydrogen, which combined with oxygen atoms present on asteroids are able to produce water. Several studies have suggested, over the years, that the same asteroid Itokawa could contain significant amounts of water, but has never been clarified where it came from.
The research of Daly and colleagues sheds new light on a fundamental question for understanding the universe and its formation: in the early stages of expansion, in fact, the universe was rich in dust, many of which may have been affected by solar winds and transformed into water.
The origin of our oceans could therefore be explained once and for all: they would be single molecules of interstellar dust that, hit by the flow of solar winds during their journey to the planet Earth, arrived on the surface of the planet in the form of water.
What makes the discovery a real turning point in the research on the origin of the Oceans is in the composition of water affected by solar winds: it is no longer the deuterium water typical of asteroids, but a form of water that contains less deuterium, much more similar to that which made possible the life on planet Earth.
According to Daly, "it is possible to produce the Earth's Oceans" by mixing together what he calls "cosmic reservoirs": stardust and solar winds would therefore be at the origin of the formation of our Oceans. Or rather, of their arrival on our planet.