Particles of space dust react with solar wind to form water around the particles’ edges, according to new research. John Bradley

The source of water on the Moon, thought to be hiding in the permanently shadowed craters at the Moon’s poles, has long eluded scientists. But new research into the ability of interplanetary dust to deliver water to planets and other celestial bodies suggests the Moon’s water may have come from outer space.

Researchers from the University of Hawaii, Manoa, the University of California, Berkeley, and California’s Lawrence Livermore National Laboratory used state-of-the-art electron microscopes to get a close-up look at particles of interplanetary space dust. What they found was that solar wind radiation had changed the outer rims on the silicate minerals in space dust to water, something scientists previously believed to be the case but weren’t able to prove because of limited technology.

Their study, published in the journal the Proceedings of the National Academy of Sciences, concluded that the water found on interplanetary dust forms from the reaction of solar wind and oxygen in the silicate mineral grains. Solar wind, which bombards the particles with ionized hydrogen atoms, reorganized the atoms in the dust particles, leaving oxygen more available to react with hydrogen to create water. Researchers say the implications of finding water on the rims of space dust are huge.

“It is a thrilling possibility that this influx of dust has acted as a continuous rainfall of little reaction vessels containing both the water and organics needed for the eventual origin of life on Earth and possibly Mars,” study co-author Hope Ishii, a researcher at the Hawaii Institute of Geophysics and Planetology, said in a statement.

Interplanetary dust, the tiny particles left over from the formation of planets, comets and asteroids, measure just a few molecules to .1 micrometers in size. Scientists have estimated that about 40,000 tons of space dust reaches the Earth’s surface every year.

In 2011, researchers first reported that interplanetary dust contains organic matter created by stars. The chemical structures of the organic material mirrored the makeup of coal and petroleum.

“Such chemical complexity was thought to arise only from living organisms, but the results of the new study show that these organic compounds can be created in space even when no life forms are present,” noted in 2011. “In fact, such complex organics could be produced naturally by stars, and at an extremely rapid pace.”

If space dust is carrying organic matter and water all over the solar system, scientists may be able to pinpoint the beginning of life on other planets using this model, or even prove that life on earth came from outer space.

"In no way do we suggest that [water formation on space dust] was sufficient to form oceans, for example,” Ishii said. "However, the relevance of our work is not the origin of the Earth's oceans but that we have shown continuous, co-delivery of water and organics intimately intermixed."

The results of the team’s research could offer an explanation for measurements of the Moon that discovered OH and preliminary water deep beneath the surface.

Scientists have always assumed the moon was a dry, waterless wasteland. With no atmosphere, sunlight decomposes water vapor and hydrogen is quickly lost to outer space. But since the 1960s, scientists have surmised that water in the form of ice could, theoretically, exist on the moon’s surface, hiding in the shadows of the Moon’s craters.

A 2009 report published in the journal Science provided data from Cassini’s visual and infrared spectrometer during its 1999 flyby that found trace amounts of hydroxyl on the Moon’s surface.

And just last year, NASA yielded evidence of water stored in mineral grains on the Moon’s surface.