Solar Wind Creates Water In Lunar Soil.
This microscope image shows a grain of agglutinate glass similar to those analyzed in the lunar surface-water study reported in Nature Geoscience. The specimen in this image, which comes from samples returned by Apollo astronauts, is smaller than a typical dust grain. Image by Yang Liu.
About the last thing you’d think would contribute to water is solar wind! However, thanks to studies done over the last five years have turned up some amazing amounts of data.
With lunar spacecraft observations and new laboratory analysis of Apollo lunar samples, researchers have now triumphed over the antiquated theory that the Moon had no water. It actually has a lot more than you might think!
Three years ago, NASA’s Lunar Crater Observation and Sensing satellite, better known as LCROSS, impacted a permanently shadowed lunar crater, resulting a a rich ejecta infused with water ice. What’s more, water and related compounds have also been found in lunar regolith. It’s presence was known, but how it got there was the real riddle. Popular conjecture was these water deposits originated from comet impacts and other space detritus. Some forty years ago, models of lunar water stability showed that hydrogen ions (protons) from solar wind might just combine with oxygen on the lunar surface to create a compound called hyroxyl – one atom of hydrogen and one of oxygen – known as OH.
In an article just published in Nature Geoscience, U-M’s Youxue Zhang and colleagues from the University of Tennessee and the California Institute of Technology present findings which show solar-wind production of water ice on the Moon. The first author of the paper is Yang Liu of U-T. She is a U-M alumna who earned her doctorate under Zhang, who is a professor in the Department of Earth and Environmental Sciences. According to the paper, the researchers revealed infrared spectroscopy and mass spectrometry analyzes of Apollo samples that reveal the presence of significant amounts of hydroxyl inside glasses formed in the lunar regolith by micrometeorite impacts. These regolith glasses are called agglutinates, and may just be a “bank” filled with OH deposits on the Moon.
“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.”
According to the news release, the findings suggest that ice inside permanently shadowed polar craters on the Moon, sometimes called cold traps, could contain hydrogen atoms which have been delivered from 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.”
Original Story Source: University of Michigan News Service. Submitted by Tammy Plotner for “Dave Reneke’s World of Space and Astronomy News”.
