Neon lights on the moon? Not quite, but NASA scientists say data from a lunar orbiter has confirmed the presence of neon in our cosmic companion's atmosphere.
NASA's Lunar Atmosphere and Dust Environment Explorer spacecraft, or Ladee, which spent seven months in orbit around the moon in late 2013, made the first-ever detection of neon in the thin lunar atmosphere.
Thin is the operative word when it comes to the lunar atmosphere, properly an "exosphere" because it's so tenuous — around 100 trillion times less dense than our planet's atmosphere at sea level, space agency scientists point out.
The detection confirmed for the first time what researchers have suspected since the 1970s and the Apollo missions, that noble gases like helium and argon — and neon — are present above the surface of the moon.
Those three elements make up most of the lunar atmosphere, likely coming to the moon in the solar wind of particles that bathe both the moon and the Earth.
"We were very pleased to not only finally confirm [neon's] presence, but to show that it is relatively abundant," says Mehdi Benna of NASA's Goddard Space Flight Center in Greenbelt, Md.
Measurements by the Neutral Mass Spectrometer instrument aboard the Ladee spacecraft showed the relative abundance of the three noble gases in the moon's exosphere changed at different times during the lunar day, the researchers said.
Argon peaked at the lunar sunrise, they explained, while neon was most abundant around 4 a.m. and helium at 1 a.m.
Not all of the gases are from the solar wind, they noted; some are likely coming from lunar rocks.
Argon results from the decay of naturally occurring radioactive potassium-40, found in rocks on the lunar surface.
Around 20 percent of the helium detected by Ladee "is coming from the moon itself, most likely as the result from the decay of radioactive thorium and uranium, also found in lunar rocks," says Benna.
Since most atmospheres around planets and moons in our solar systems are exospheres — the Earth being the notable exception — scientists are glad of any chance to learn more about them.
That chance may be a fleeting one when it comes to the moon, says Benna, as future human missions there, whether by robotic spacecraft like Ladee or perhaps permanent human settlement, could disturb the exosphere through rocket exhaust or emissions from a permanent base.
"It's critical to learn about the lunar exosphere before sustained human exploration substantially alters it," he says.
