October 14, 2012 in Space
The solar wind appears to be the source of the water that has been found on the moon, according to new research. The water that is locked inside the lunar soils was very likely formed from the interaction of oxygen particles on the moon’s surface with the charged particles streaming from the sun, researchers from the University of Michigan have suggested.
The discovery of water on the moon was fairly recent; during just the last five years, numerous spacecraft observations and new analysis’s of the lunar samples taken by Apollo missions “have overturned the long-held belief that the moon is bone-dry.”
NASA’s Lunar Crater Observation and Sensing satellite (LCROSS) was crashed into a permanently shadowed lunar crater in 2009, ejecting a plume of lunar material that was very dense with water ice. And the lunar regolith itself has been shown by various means to contain water, the regolith is what covers the lunar surface, a very fine layer of dust and rock fragments.
The source of this water has remained a debated point though. The primary theories have been that it was deposited by comets or other space debris. But theoretical models of “lunar water stability dating to the late 1970s suggest that hydrogen ions (protons) from the solar wind can combine with oxygen on the moon’s surface to form water and related compounds called hydroxyls, which consist of one atom of hydrogen and one of oxygen and are known as OH.”
But in the new research, infrared spectroscopy and mass spectrometry analyses of lunar samples taken by Apollo have shown that there are significant amounts of hydroxyl inside the glasses that are present in the samples. These glasses were created in the samples by micrometeorite impacts on the moon.
The researchers then used various techniques to determine the chemical form of the hydrogen present as well as it’s isotopic composition.
“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 Zhang, the James R. O’Neil Collegiate Professor of Geological Sciences.
“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.”
The research implies that the ice in polar craters on the moon may also contain hydrogen atoms that could be traced back to the solar wind.
“This also means that water likely exists on Mercury and on asteroids such as Vesta or Eros further within our solar system,” Liu said. “These planetary bodies have very different environments, but all have the potential to produce water.”
The new research was just published in the journal Nature Geoscience.
Source: University of Michigan
Image Credits: Yang Liu; Moon via Wikimedia Commons