Washington, June 19 (ANI): NASA's Interstellar Boundary Explorer (IBEX) spacecraft has made the first observations of very fast hydrogen atoms coming from the Moon, following decades of speculation and searching for their existence.
During spacecraft commissioning, the IBEX team turned on the IBEX-Hi instrument, built primarily by Southwest Research Institute (SwRI) and the Los Alamos National Laboratory, which measures atoms with speeds from about half a million to 2.5 million miles per hour.
Its companion sensor, IBEX-Lo, built by Lockheed Martin, the University of New Hampshire, NASA Goddard Space Flight Center, and the University of Bern in Switzerland, measures atoms with speeds from about one hundred thousand to 1.5 million mph.
"Just after we got IBEX-Hi turned on, the Moon happened to pass right through its field of view, and there they were," said Dr. David J. McComas, IBEX principal investigator and assistant vice president of the SwRI Space Science and Engineering Division.
"The instrument lit up with a clear signal of the neutral atoms being detected as they backscattered from the Moon," he added.
From its vantage point in space, IBEX sees about half of the Moon - one quarter of it is dark and faces the nightside (away from the Sun), while the other quarter faces the dayside (toward the Sun).
Solar wind particles impact only the dayside, where most of them are embedded in the lunar surface, while some scatter off in different directions.
The scattered ones mostly become neutral atoms in this reflection process by picking up electrons from the lunar surface.
The IBEX team estimates that only about 10 percent of the solar wind ions reflect off the sunward side of the Moon as neutral atoms, while the remaining 90 percent are embedded in the lunar surface.
Characteristics of the lunar surface, such as dust, craters and rocks, play a role in determining the percentage of particles that become embedded and the percentage of neutral particles, as well as their direction of travel, that scatter.
According to McComas, the results also shed light on the "recycling" process undertaken by particles throughout the solar system and beyond.
The solar wind and other charged particles impact dust and larger objects as they travel through space, where they backscatter and are reprocessed as neutral atoms.
These atoms can travel long distances before they are stripped of their electrons and become ions and the complicated process begins again.
The combined scattering and neutralization processes now observed at the Moon have implications for interactions with objects across the solar system, such as asteroids, Kuiper Belt objects and other Moons. (ANI)