The Moon’s thin atmosphere contains neon, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft has confirmed.
“The presence of neon in the exosphere of the moon has been a subject of speculation since the Apollo missions, but no credible detections were made,” said Mehdi Benna of NASA’s Goddard Space Flight Center in Greenbelt, Maryland and the University of Maryland, Baltimore County in a NASA press release. “We were very pleased to not only finally confirm its presence, but to show that it is relatively abundant.”
Because the Moon’s atmosphere is so tenuous, about 100 trillion times less dense than Earth’s atmosphere are sea level, the volume of neon is minute.
Most of the gases in the exosphere — primarily neon, argon, and helium — comes from the solar win, a stream of electrically conducting gas blown from the surface of the sun into space at about one million miles per hour. All of these elements impact the Moon, but only helium, neon and argon are volatile enough to return to space. A portion of the helium, argon, and neon in the lunar exosphere comes from naturally occurring radioactive potassium-40, thorium, and uranium found naturally in lunar rocks.
Launched in September 2013, from NASA’s Wallops Flight Facility in Virginia, LADEE orbited the Moon from Oct. 6, 2015, to Nov. 10, 2015.
The level of argon varied over time by about 25% over the course of the LADEE mission. Benna conjectured that a transient source of argon may come from outgassing from the surface triggered by tidal stress on the Moon.
In addition to its use in signs, neon is used to make high-voltage indicators and switching gear, lightning arresters, diving equipment, and lasers. Liquid neon is a cryogenic refrigerant, with 40 times more refrigerating capacity per unit of volume than liquid helium and three times that of liquid hydrogen.