The hydrogen discovered in the asteroid dust suggests more than half of the Earth's water comes from space rocks

Scientists have detected traces of water in the dust of a supposedly dry asteroid, adding a new support to a theory that could explain the creation of the Earth's oceans.

In a new study, researchers at Arizona State University re-examined samples taken by the first Japanese Hayabusa probe in 2010.

The spacecraft captured about 1,500 particles in total when it visited the asteroid Itokawa during the first-ever asteroid sampling mission.

The new analysis revealed a substantial amount of water and hydrogen compositions "indistinguishable from the Earth," suggesting that water-rich asteroids are much more common than previously thought.

The researchers now claim that the impact of a similar asteroid in the history of our planet could have generated half of the Earth's water.

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"We found that the samples we examined were enriched in water compared to the average of the objects in the inner solar system," said postdoctoral scholar Ziliang Jin.

Itokawa is what is called an S-type asteroid and is thought to have detached from a larger object at least 12 miles wide.

It is approximately 1,800 feet long and 700 to 1,000 feet wide and circling the sun every 18 months.

"S-type asteroids are one of the most common objects in the asteroid belt," said co-author Maitrayee Bose.

"They initially formed at a distance from the sun equal to a third or three times the distance from the Earth."

Despite a series of impacts on the Itokawa of today, millions of years ago, the asteroid has retained its water.

"The particles we analyzed came from a part of Itokawa called the Sea of ​​Muses," says Bose.

"This is a place of the asteroid smooth and covered with dust."

"Although the samples were collected on the surface, we do not know where these grains were in the original parent body," Jin adds.

"But our best guess is that they were buried more than 100 meters deep."

"The minerals have isotopic compositions of hydrogen that can not be distinguished from the Earth," Jin said.

In the samples, each of which represents only half the thickness of a human hair, the researchers found surprising amounts of water.

The discovery suggests that these asteroids, supposedly dry, may contain much more water than previously thought.

"This means that S-type asteroids and parent bodies of ordinary chondrites are probably a critical source of water and several other elements for terrestrial planets," Bose said.

"And we can only say that thanks to the in situ isotopic measurements carried out on samples of regolith of returned asteroids – their dust and their superficial rocks.

"This makes these asteroids high priority targets for exploration."