Traces of Water Found in Old Moon Rocks from Apollo Threatens Theory of How Moon was Formed
Researchers from the University of Michigan announced today the discovery of tiny amounts of water in the moon rocks brought back to Earth by the Apollo missions were native water, and not water brought by meteors or other objects from space crashing into it. This discovery could in turn invalidate the current theory of how our Moon was formed.
The researchers analyzed the mineral grains from the lunar highlands, a region that is assumed to represent the original crust that crystallized from a mostly molten young moon. The researchers, the results of their analysis imply that the lunar core contained water during the molten stage before the crust solidified. This unfortunately does not fit with the dominant theory regarding the Moon's formation, which is that the moon formed from the debris generated during a massive impact with the proto-Earth and any water in lunar rocks was added after its formation by smaller meteorite impacts or solar wind.
UM researcher Youxue Zhang said:
"Because these are some of the oldest rocks from the moon, the water is inferred to have been in the moon when it formed. That 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. Under that model, the hot ejecta should have been degassed almost completely, eliminating all water."
Using a method known as fourier-transform infrared spectroscopy, the scientists re-analyzed the water content by determining hyrdroxyl groups used in the old samples. The traces found in the moon rocks amount to a content of just 6 parts per million of water, which is drier than any desert on Earth but still much more than expected to have survived in a rock from the once-molten center of the moon. Researchers say that the samples should have been bone dry.
Based on their measurements, the researchers estimated that the early moon's magma ocean could have contained up to 320 parts per million of water. When that ocean mostly crystalized, the remaining residues could have had as much as 1.4 percent water, which might explain the measured water content of the lunar rocks brought back to Earth by the early 1970s Apollo missions.
The researchers said that the new findings imply that the early moon was somewhat wet and that water wasn't completely lost during its formation.