New Study Explains Puzzling Presence of Molecular Hydrogen Observed in NASA's LCROSS Mission

Discovering molecular hydrogen on the Moon was a surprise result from NASA's Lunar Crater Observation Sensing Satellite (LCROSS) mission, which crash-landed the LCROSS satellite's spent Centaur rocket into the Cabeus crater in the permanently shadowed region of the Moon. Now, nearly four years later, scientists from the University of New Hamsphire and NASA's Goddard Space Flight Center believe they have discovered the reason behind the mysterious metamorphosis of the Moon's water ice.

The region where the rocket landed is interesting to scientists because, as a result of having remained at temperatures of near absolute zero for billions of years, the spot has long preserved the pristine nature of the lunar soil, or regolith.

Instruments on board LCROSS trained on the resulting immense debris plume were quick to detect water vapor and water ice, fulfilling a main purpose of its mission. Meanwhile, the Lunar Reconnaissance Orbiter (LRO), already in orbit around the Moon, noted the unplanned discovery of molecular hydrogen.

After the finding, ideas were passed around but none of them, according to lead author Andrew Jordan, a scientist at UNH's Institute for the Study of Earth, Oceans and Space (EOS), seemed to work in regards to the conditions in the crater or with the rocket impact.

On the other hand, he explains, the new analysis conducted by him and his team shows that the galactic cosmic rays, consisting of charged particles with enough energy to penetrate below the lunar surface, "can dissociate the water, H2O, into H2 through various potential pathways."

Based on data gathered by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument aboard the LRO spacecraft, the idea was first posited by Jordan's colleague co-author of the paper Nathan Schwardron.

CRaTER, meanwhile, came in handy by characterizing the global lunar radiation environment by measuring radiation dose rates from galactic cosmic rays and solar energetic particles, according to the researchers.

"We used the CRaTER measurements to get a handle on how much molecular hydrogen has been formed from the water ice via charged particles," Jordan explained.

Jordan's computer model then incorporated the CRaTER data to show that these energetic particles can form between 10 and 100 percent of the H2 measured.

The study notes that in order to come to a more precise result, particle accelerator experiments on water ice are required in order to more accurately gauge the number of chemical reactions that result per unit of energy deposited by cosmic rays and solar energetic particles.

Published in the Journal of Geophysical Research: Planets, the study can be accessed here.