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Solar wind particles likely source of water on moon’s surface, according to study

After more than three decades of lunar study, scientists have determined that solar wind is the unlikely source of water on the moon. In a study published online October 14, 2012, in the journal Nature Geoscience, researchers from a variety of educational institutions announced a theory as to how lunar water forms and under what conditions.

Over the last five years, researchers from the University of Tennessee, University of Michigan, and the California Institute of Technology have worked diligently to overturn the moon’s reputation as a bone-dry desert, according to a U-M statement that was obtained by e! Science News. Using new lab measurements of Apollo mission samples alongside spacecraft observation, researchers were able to determine the presence of the life-giving compound on the moon.

NASA’s Lunar Crater Observation and Sensing satellite (LCROSS) crashed into a permanently shadowed crater as recently as 2009, drawing attention to the anomaly by ejecting an immense plume of surprisingly water-rich material.  Although scientists agree on the presence of water and related compounds on the moon, theoretical models of lunar water stability range from impact sources, such as comets and space debris, to a model based on the ionic hydrogen provided by solar wind.

Thanks to the work of Professor Youxue Zhang of the University of Michigan’s Department of Earth and Environmental science, and the lead author of the paper, his former U-M doctoral student Yang Liu and her team from the University of Tennessee, the solar wind model has been proven correct.

“We found that the ‘water’ component, the hydroxyl, in the lunar regolith is mostly from solar wind implantation of protons, which locally combined with oxygen to form hydroxyls that moved into the interior of glasses by impact melting,” said Prof. Zhang in a statement.

“Lunar regolith is everywhere on the lunar surface, and glasses make up about half of lunar regolith. So our work shows that the ‘water’ component, the hydroxyl, is widespread in lunar materials, although not in the form of ice or liquid water that can easily be used in a future manned lunar base.”

Researchers were able to use individual grains of regolith glasses known as agglutinates from various lunar locations gathered on Apollo missions 11, 16, and 17 to determine the presence of hydroxyl on the moon.

Contextualizing the discovery in terms of future exploration, Dr. Liu extrapolates, saying, “This also means that water likely exists on Mercury and on asteroids such as Vesta or Eros further within our solar system.” She adds, “These planetary bodies have very different environments, but all have the potential to produce water.”