Researchers from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, created the first comprehensive map of hydrogen abundances on the surface of the Moon using data gathered more than 20 years ago. The map indicates two categories of lunar minerals with enhanced hydrogen. It supports earlier hypotheses concerning lunar hydrogen and water, including the finding that water was probably involved in the original magma-ocean creation and solidification of the Moon.
The World Map of Lunar Hydrogen
NASA Ames Research Center's Rick Elphic, David Lawrence, Patrick Peplowski, and Jack Wilson used the orbital neutron data from the Lunar Prospector mission to create the map. NASA launched the probe in 1998, and it orbited the Moon for a year and a half, sending back the first direct evidence of enhanced hydrogen near the lunar poles before crashing into the lunar surface.
Cosmic rays, or high-energy protons and neutrons that travel through space at almost the speed of light, are produced when stars explode. These cosmic rays split the atoms present on a planet's surface or a moon, launching protons and neutrons into the air. By observing the mobility of those protons and neutrons, scientists may identify an element and establish where and how much of it is present.
Lawrence compared the phenomenon with the game of pool. He represented nitrogen as the cue ball while the billiard balls were hydrogen. It is like when a billiard ball strikes a cue ball; the cue ball dies and stops moving, and the billiard ball is sent into motion because both objects have the same mass. Similarly, when a neutron comes into contact with hydrogen, it dies and stops moving, and the hydrogen is put into motion.
The Neutron Spectrometer was one of five instruments used to calibrate the data to quantify the amount of hydrogen by the proportional drop in neutrons observed by the device. The spectrometer is one of five instruments mounted aboard Lunar Prospector to complete gravitational and compositional maps of the Moon.
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Enhanced Hydrogen Connected to the Origin of the Moon
Lawrence said they were able to combine data from lunar soil samples from the Apollo missions with what they had measured from space. Then put together a complete picture of lunar hydrogen for the first time.
Based on the map, there was the presence of enhanced hydrogen in two different types of lunar materials. These two types include the Aristarchus Plateau and KREEP-type rocks.
The first type is home to the largest pyroclastic deposit on the Moon. These deposits, which are rock fragments, support earlier findings suggesting hydrogen and/or water played a part in lunar magmatic events.
The name of the second type is an acronym. K stands for potassium, REE for rare Earth elements, and P for phosphorus.
According to Lawrence, the Moon was molten debris from a huge impact on Earth when it first formed. The last sort of material to crystallize and become hard is believed to be KREEP. As it cooled, minerals crystallized out of the melt.
Yet, the new map showed not only the complete list of hydrogen on the Moon, but it may also enable scientists to estimate how much water and hydrogen were on the Moon at the time of its formation.
The research was published in Wiley Online Library.
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