Water discovered in Apollo lunar rocks may challenge theory of moon’s origin

February 18, 2013

Water discovered in Apollo lunar rocks may challenge theory of moon’s origin

Water in the moon? It seems so.

According to a new study, the long accepted theory of how the moon was formed may have to be reexamined.

A recent study has revealed that the interior of the moon held water early in its lunar history. Some scientists speculate this new information may clash with the current explanation for how the moon was formed.

Examining samples collected from the moon during the Apollo missions,  a research team at the University of Michigan has determined that the interior of the moon used to contain water . The samples that were studied were collected from the lunar highlands, which is considered the original lunar crust. At its start, the moon was made mostly of molten material until the crust solidified into the moon we see now. The new study suggests that there was water present within the moon while it was still in its molten phase.

Until now, most scientists have agreed that the moon was formed by debris leftover from a small-body planet impact with Earth. According to this theory, any water found on the moon was brought there after its formation by solar winds or small meteorites. In essence, the new research says the moon contained water before it solidified while the old theory insists water was brought to the lunar surface after its formation by various objects on impact.

“Because these are some of the oldest rocks from the moon, the water is inferred to have been in the moon when it formed,” said Youxue Zhang of the University of Michigan. “This is somewhat difficult to explain with the current popular moon-formation model, in which the moon formed by collecting the hot ejecta as the result of a super-giant impact of a martian-size body with the proto-Earth.”

Zhang said if the old model was correct, the hot ejecta would have degassed the moon completely, eliminating all traces of water on the lunar surface. Following examination of the lunar samples under a microscope equipped with a spectrometer, the team of researchers discovered that the rocks contain 6 parts per million of water. The amount is far less than that found on Earth’s driest deserts, but it far exceeds previous estimates related to the lunar debris theory. According to the Michigan researchers, the amount translates to the  moon’s magma ocean containing upwards of 320 parts per million of water.

The study follows in the wake of a number of studies aimed at better understanding the moon’s early days. A study released last year announced the discovery of small amounts of water on the moon’s surface, which researchers say arrived via small asteroids and comets sent smashing into the lunar surface. Earlier this year, a pair of NASA probes were directed to crash land in the side of a lunar mountain, providing scientists with a wealth of data related to the moon’s subsurface. The pair of probes spent much of the previous year relaying information on the moon’s gravitational field back to Earth.

Although the formation of the moon was thought to be a solved mystery, its validity seems to be in question. Whether or not researchers decide to take the challenge to determine how the moon was created once and for all is still up in the air.

The findings were published online Sunday in the journal Nature Geoscience.


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