NASA moon spacecraft makes icy find as it celebrates orbital anniversary
Sen—A NASA lunar spacecraft celebrated four years in orbit with a discovery that could help scientists understand how radiation alters water ice in the Solar System.
The Lunar Reconnaissance Orbiter (LRO) uncovered evidence that energetic particles, pummelling the Moon's soil, produce molecular hydrogen from water ice on the lunar surface.
Cosmic rays, many of which originate beyond the Solar System, have enough energy to plumb through the Moon's regolith and transform the water (which has hydrogen and oxygen molecules within it) into molecular hydrogen.
This helps explain a surprising hydrogen find from another NASA mission, scientists said. The mechanism also could produce water ice changes in planets and moons nearby to Earth.
Traditionally, the Moon was considered a place frozen in time that had little activity associated with it beyond the rain of micrometeorites churning up regolith -- as well as the occasional larger rock that produced a crater.
Research a few decades ago, however, revealed that the Moon has a tenuous atmosphere (more properly referred to as an "exosphere") made up of charged particles. These ions were likely produced at the surface as a result of interactions with micrometeorites, plasma in Earth's magnetosphere and the Sun itself, stated the American Geophysical Union in a 2010 description of the moon's environment.
Then in 2009, NASA's Lunar CRater Observation and Sensing Satellite (LCROSS) discovered hydroxyl (a close cousin to water) that was generated after the upper stage of its rocket smashed into a permanently shadowed crater in the Moon's south pole. LRO also saw molecular hydrogen at the same location.
"After the finding, there were a couple of ideas for how molecular hydrogen could be formed but none of them seemed to work for the conditions in the crater or with the rocket impact," stated Andrew Jordan, the lead researcher and a scientist at the University of New Hampshire's Institute For The Study of Earth, Oceans, and Space.
An instrument aboard LRO examined the radiation dose from cosmic rays and solar particles to provide a picture of the overall global environment. Scientists then created a model that shows the particles could make anywhere between 10 and 100 percent of molecular hydrogen observed.
"Our analysis shows that the galactic cosmic rays, which are charged particles energetic enough to penetrate below the lunar surface, can dissociate the water, H2O, into H2 through various potential pathways," Jordan added.
The research was published this month in the Journal of Geophysical Research: Planets just days before the June 19 anniversary of LRO's orbital insertion.
In four years of circling the moon, LRO has uncovered information that could assist with future robotic and, possibly, human exploration of the Moon. For example, one of its instruments analyzed the amount and type of radiation surrounding the Moon and concluded that plastics, which are a lighter type of shielding than some alternatives, would be adequate to protect humans against these particles.
A three-dimensional view of the Apollo 17 landing site (arrow) and surrounding areas based upon data generated by the Lunar Reconnaissance Orbiter. Credit: NASA/Goddard/Arizona State University/Smithsonian
LRO also released data showing that the Moon is still shrinking. It additionally provided high-definition views of human landing sites and associated human activity spots generated by the Apollo missions between 1968 and 1972.
The spacecraft's mission will go to at least October 2014, providing its electronics and mechanics hold up, and could be extended for another two years if NASA's budget allows for it.
"Not only has LRO delivered all the information that is needed for future human and robotic explorers, but it has also revealed that the moon is a more complex and dynamic world than we had ever expected," stated Rich Vondrak, LRO deputy project scientist.