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Researchers detect neon in the Moon’s exosphere

David Dickinson, Correspondent
Aug 20, 2015, 23:38 UTC

Sen—Researchers announced this week that NASA’s most recent mission to the Moon discovered a rare inert gas where you would least expect to find it.

The finding comes from NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE). Launched in 2013 atop a converted Intercontinental Ballistic Missile from Wallops Island Virginia, LADEE spent seven months characterizing the near lunar environment.

The element in question is the noble gas neon. This is the same familiar neon used in electric signs here on Earth. Scientists have speculated about the existence of neon in the thin lunar atmosphere—known as the exosphere—for decades.

“The presence of neon in the exosphere of the Moon has been the subject of speculation since the Apollo missions,” said Goddard Space Flight Center’s Mehdi Benna in a press release.

LADEE’s Neutral Mass Spectrometer (NMS) instrument obtained the findings in the study.

Researchers refer to the atmosphere of the Moon as an “exosphere” because it is so tenuous. For the most part, we consider the Moon to be “airless,” with a density less than one trillionth the atmospheric pressure at sea level here on Earth. The surface of the Moon is a better vacuum than any scientist can create in a laboratory on Earth.

Early Apollo astronauts and the Surveyor spacecraft first made note of a mysterious twilight glow in the skies on and surrounding the Moon in the late 1960s. Missions such as LADEE have proven the existence of gas and dust surrounding the Moon, often the product of outgassing and micrometeoroid impacts. Solar wind—a constant stream of particles emanating from the Sun—is the main source of inert gases such as helium, argon, and neon found in the lunar environment. Composed mainly of hydrogen and helium particles, the solar wind slams into the Moon’s surface, but trace amounts of neon and argon also hitch a ride and can linger in the lunar environment.

Researchers also discovered that the amount of argon, helium and neon vary according to the time of day on the Moon, and this rate of release even varied over the course of the LADEE mission. Another prime source of the isotope argon-40 is the radioactive decay of potassium-40.

“The data collected by the NMS addresses the long-standing questions related to the sources and sinks of exospheric helium and argon that have remained unanswered for four decades,” said Benna in a statement.

The possibility of mining the isotope Helium-3 on the surface of the Moon is especially intriguing. Scarce on Earth, Helium-3 could, in theory, be used in fusion reactors, and make space exploration a viable enterprise.

Far from dead, the Moon continues to tantalize and fascinate.

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