NASA's LADEE ran out of fuel and crashed into the lunar surface in 2014, but not before it collected the data needed to answer some decades-old questions about the moon. One of those is confirming that our natural satellite's atmosphere contains neon -- the same gas used to light up signs in Vegas. Astronomers have been speculating about its presence since the Apollo missions, and now LADEE's Neutral Mass Spectrometer (NMS) instrument has proven that it exists. It's even relatively abundant, though the moon's atmosphere is too thin (it's actually called "exosphere" due to that reason) to turn it into a glowing orb in the sky.
NMS has thus proven that the lunar exosphere is composed mostly of helium, argon and neon. Their main source is solar winds, and they fluctuate over time, as well as exhibit peak times throughout the day. LADEE's data shows, however, that some of the gases in the exosphere come from the moon itself: The decay of radioactive potassium-40 found in lunar rocks gives rise to argon, while thorium and uranium produce helium.
As NASA's Goddard's Mehdi Benna said:
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. These discoveries highlight the limitations of current exospheric models, and the need for more sophisticated ones in the future.
[Image credit: NASA Ames/Dana Berry]