Creating the first global map of lunar hydrogen

(ORDO NEWS) — Using data collected more than two decades ago, scientists at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, have compiled the first complete map of the hydrogen content on the Moon‘s surface.

The map identifies two types of lunar materials containing enriched hydrogen, confirming previous ideas about lunar hydrogen and water, including the conclusion that water may have played a role in the initial formation and solidification of the magma ocean on the Moon.

David Lawrence, Patrick Peplowski and Jack Wilson of APL, along with Rick Elphick of NASA‘s Ames Research Center, used orbital neutron data from the Lunar Prospector mission to build their map.

The probe, which was deployed by NASA in 1998, orbited the moon for a year and a half and sent the first direct evidence of increased hydrogen content at the lunar poles before colliding with the lunar surface.

When a star explodes, it emits cosmic rays, or high-energy protons and neutrons, that travel through space at nearly the speed of light.

When these cosmic rays come into contact with the surface of a planet or moon, they shatter the atoms on those bodies, sending protons and neutrons flying.

Scientists can identify the element and determine where and how much it exists by studying the movement of these protons and neutrons.

“Imagine you are playing pool, where the cue ball is neutrons and the billiard balls are hydrogen,” Lawrence explains. “When you hit a billiard ball with a cue ball, the cue ball stops moving and the billiard ball starts moving because both objects have the same mass.

In the same way, when a neutron comes into contact with hydrogen, it dies and stops moving, and hydrogen starts moving. So when we see fewer neutrons moving, it indicates that hydrogen is present.”

The team calibrated the data to quantify the amount of hydrogen against the corresponding decrease in the number of neutrons measured by the Neutron Spectrometer, one of the five instruments installed on the Lunar Prospector for compiling gravitational and compositional maps of the Moon. The results were published in the Journal of Geophysical Research: Planets.

“We were able to combine data from lunar soil samples from the Apollo missions with what we measured from space, and for the first time compiled a complete picture of lunar hydrogen,” Lawrence continued.

The team’s map confirms the elevated hydrogen content of two types of lunar materials. The first is the largest pyroclastic deposit of the Moon, located on the Aristarkh plateau.

These deposits are rock fragments erupted by volcanoes, confirming previous observations that hydrogen and/or water played a role in lunar magmatic events.

The second is KREEP type breeds. KREEP is the abbreviation for lunar lava rock, standing for potassium (K), rare earth elements (REE), and phosphorus (P).

“It is generally accepted that the Moon originally formed from molten debris from a huge impact with the Earth,” Lawrence said. “As the melt cooled, minerals formed, and KREEP is believed to be the last type of material to crystallize and solidify.”

Lawrence was part of the original team that studied the first data from the Lunar Prospector mission in 1998. He stated that it took considerable time to complete a map of Earth’s nearest neighbor.

“It took several years to complete the analysis,” Lawrence said. “As we parsed what we got, we began to correct the data, which, as it turned out, was not hydrogen.

We have gone back and refined previous analyzes, and were largely able to do so thanks to findings from other missions. We always build on previous knowledge and thus pave the way for new ones.”

This new map not only completes the inventory of hydrogen on the Moon, but could also lead to a quantification of hydrogen and water at the time of the moon’s birth.

In 2013, APL researchers also confirmed the presence of water ice at the poles of the planet Mercury using data from the neutron spectrometer on the APL-built MESSENGER spacecraft.

These discoveries are important not only for understanding the solar system, but also for planning its future research by mankind.


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