Asteroids May Feed the Moon's Water Supply Through Collisions

Could asteroids be the moon's main "water supply?" Researchers have found that water reserves on the moon are the result of asteroids acting as "delivery vehicles" and not due to falling comets, as previously thought.

During the days of the Apollo program, scientists believed that the moon was completely dry. The absence of an atmosphere and the influence of solar radiation were thought to be enough to evaporate all volatile substances into space. However, in the 1990s researchers found from the Lunar Prospector probe that this wasn't the case; there was ice on the moon.

In recent years, lunar missions have brought scientists two pieces of information: there are considerate quantities of water and hydroxyl groups in the near-surface soil on the moon, and there's a certain water distribution on the moon's surface.

This water distribution, though, did not correspond to the map of "cold traps," where researchers believed the water should be located. The researchers therefore had to refine their theory to say that water was able to survive under a soil blanket.

But where did the water come from in the first place? Researchers proposed comets may have hit the moon, bringing water with them. However, researchers have now found that asteroids may be to blame. Asteroids can contain up to 10 percent of water, and are protected against the heat encountered durin impact with the help of chondrites.

"We've concluded that the fall of asteroids containing water could generate 'deposits' of chemically bounded water inside some lunar craters," said Valery Shuvalov, one of the researchers, in a news release. "The fall of one two-kilometer size asteroid with a rather high proportion of hydrated minerals could bring to the moon more water than all of the comets that have fallen over billions of years."

The findings are published in the journal Planetary and Space Science.

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