Water ice is the most abundant solid material in the universe. Much of it was created as the byproduct of star formation, but not all. John Bradley of Lawrence Livermore National Laboratory and his team may have discovered a new source of water in our solar system. His lab experiments reveal that the solar wind may be creating water on interplanetary dust.

The sun ejects high-speed charged particles in all directions. Bodies in the inner solar system get bombarded by this wind of particles, which continuously varies in intensity.

Small bodies, such as dust particles or tiny asteroids, can be eroded by these harsh winds. Larger bodies that do not have an atmosphere, such as the Moon, are bombarded by both the solar wind and tiny meteorites. This form of bombardment causes a phenomenon called space weathering. (Atmospheres protect planets from tiny meteorites, while a magnetic field can deflect solar winds.)

[...]

The best way to determine whether water forms on silicate rims is to do these experiments on the types of silicate material that exist in space. Bradley did this by using three types of these minerals: olivine, clinopyroxene, and anorthine. These were exposed to charged hydrogen and helium particles, which were a proxy for the solar wind.

If water is formed by the solar wind, it would only be found in the samples that were exposed to hydrogen – not in those exposed to helium. And that is what happened. As reported in the Proceedings of the National Academy of Sciences, Bradley's sensitive tests repeatedly found water, but only in the samples that were bombarded by hydrogen.

Martin McCoustra at Heriot-Watt University in Edinburgh finds the work convincing. He said: "I am not very surprised that water could be formed on silicates. However, now that they have shown that it can, it could be an important source of water."

Bradley's work implies that water molecules must have been forming for billions of years on interplanetary dust particles, on the Moon, and possibly on asteroids. However, McCoustra warns that "This source of water, albeit new, won't be able to account for a large proportion of water in the solar system. Most of that water was formed during the process of star formation that our sun went through."

Some have argued that water-rich comets planted water on our planet. But McCoustra reckons that a single-source is unlikely. And this study provides another potential source for the material that helps make our planet habitable.

Early Earth's accidental deluge via water-carrying comets has long been a stumbling block for those interested in life on other planets.
Scientists agree that life needs water to evolve. But if water only arrives through chance impacts with comets, then life elsewhere might indeed be rare.

Water is common among the meteorites and other small bodies whose collisions formed the Earth, but scientists have long believed that the intense heat of the events dried out the young planet. Water must have arrived later, splashing down from comets after the planet was formed.

New research, however, is changing that view. Evidence is mounting that the planet's water arrived early, during formation, aboard meteorites and small bodies called "planetesimals." The work also suggests that though the planet-forming collisions were so energetic that they led to oceans of magma and widespread melting, even the intense heat would not have dried out the planet completely.

The emerging view of a watery birth for the Earth has raised the hopes of scientists seeking extrasolar life. If the presence of water isn't left to chance collisions but instead is a product of the planet-forming process, then oceans where life can evolve may be common after all.

"It is very possible that many planets are born with liquid water oceans," said Linda Elkins-Tanton, director of the Carnegie Institution for Science's Department of Terrestrial Magnetism.

[...]