Solar Winds Could Have Helped Deliver Water to Earth and Make Oceans

Solar winds could have played a major role in delivering water to Earth, new research has found, potentially solving the mystery of how our planet's oceans formed.

The mechanism could potentially help astronauts of future space missions generate water from little more than solar winds—charged plasma from the sun—and dust.

Previous research has put forward that much of Earth's water was delivered from space by asteroid impacts early in its 4.6 billion-year history. This supposition has been supported by the discovery of asteroids that are surprisingly high in water content.

The problem has been that this mechanism alone can't account for just how much water there is on Earth. And there is a further problem; the water that would have been delivered to Earth via asteroids should contain a higher proportion of heavy hydrogen-deuterium than is found in Earth's water table.

Researcher Luke Daly, of the University of Glasgow, U.K., and his team think the solution to this mystery lies with streams of charged particles, mainly hydrogen ions, emitted by the sun. These are more commonly known as solar wind.

In a study published in the journal Nature Astronomy the scientists suggest hydrogen atoms in solar winds strike asteroids, combining with oxygen atoms and creating water. That water was deposited on Earth by asteroid collisions with the planet, the paper says.

Because the early solar system was a very dusty place, the team believes that the process could have occurred in free-floating dust particles also. This means that alongside asteroids, water-rich dust could have rained down from space, delivering the planet's oceans.

"This solar wind-derived water produced by the early solar system is isotopically light [containing hydrogen rather than deuterium]," Daly said. "That strongly suggests that fine-grained dust, buffeted by the solar wind and drawn into the forming Earth billions of years ago, could be the source of the missing reservoir of the planet's water."

Daly told Newsweek: "There are two cool implications from this result. Firstly, every rocky airless world in our galaxy that is affected by the solar wind will have a renewable resource of water on its surface, this will be a key resource for human space exploration as water is vital for life and can also be used to make rocket fuel to help humanity reach for the stars.

"Second, the fact that the solar wind can implant a lot of water into tiny dust grains means that solar wind-generated water in tiny dust particles might be quite a significant unaccounted for a water reservoir in our solar system and could have contributed to the formation of Earth's oceans."

The team reached their conclusion by examining samples of the asteroid Itokawa, which were collected by the Japanese space probe Hayabusa and returned to Earth in 2010.

They used a technique called atom probe tomography, which allowed them to take an incredibly detailed look inside the first 50 nanometres or so of the surface of dust grains from Itokawa.

The paper's co-author and Curtin University Distinguished Professor at the School of Earth and Planetary Sciences, Phil Bland, revealed that the mechanism discovered by the team could account for a large amount of water.

He said: "It allowed us to see that this fragment of space-weathered rim contained enough water that, if we scaled it up, would amount to about 20 liters for every cubic meter of rock."

The discovery made by the researchers could have implications beyond the limits of our world, also. Not only could it help understand how worlds both inside and outside the solar system came to have water, an essential ingredient for life, but it could also help astronauts generate their own water supplies on space missions.

"One of the problems of future human space exploration is how astronauts will find enough water to keep them alive and accomplish their tasks without carrying it with them on their journey," University of Hawai'i at Mānoa professor and paper co-author, Hope Ishii, said. "We think it's reasonable to assume that the same space weathering process which created the water on Itokawa will have occurred to one degree or another on many airless worlds like the Moon or the asteroid Vesta."

Ishii added that it could mean that space explorers may well be able to process fresh supplies of water straight from the dust on the planet's surface. She concluded: "It's exciting to think that the processes which formed the planets could help to support human life as we reach out beyond Earth."

Daly concluded: "The next time you're sitting and drinking a glass of water, ponder the thought that up to half of the water you're drinking was once sunshine."

Update 12/2/21, 7:39 a.m. ET: This article was updated to include comments from researcher Luke Daly.