The cloud consists of dust grains kicked up from the surface by the impact of high-speed, dust particles, such as those from the Geminid meteor showers that occur each December. When a comet collides with the Moon, a single dust particle lofts thousands of smaller dust specks into the surroundings.
Our Moon’s dusty haze was first discovered using data from NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE), which launched in September 2013 and orbited the Moon for about six months. During this time, a detector on board called the Lunar Dust Experiment (LDEX) documented more than 140,000 impacts – that’s a lot of dust.
"Identifying this permanent dust cloud engulfing the moon was a nice gift from this mission," Professor Mihaly Horanyi, the principal investigator on LDEX and lead study author, said in a statement. "We can carry these findings over to studies of other airless planetary objects like the moons of other planets and asteroids."
So how have we not previously known about this massive collection of dust on the Moon, our closest celestial neighbor? While there have been hints at its existence, scientists didn’t find definitive proof until now. Horanyi and his colleagues, from the University of Colorado (UC) at Boulder, say the first evidence of a dust cloud around the Moon came in the late 1960s when NASA cameras aboard unmanned moon landers took images of a bright glow during lunar sunsets.
Several years later, Apollo astronauts orbiting the Moon also noticed a luminous glow – too bright to be explained by the Sun’s rays at that location. Now, new evidence indicates that this mysterious glow is emanating from the Moon’s lopsided dust cloud, which has built up over several billion years.
While this latest research tells us more about our lunar neighbor, it also has practical applications for space travel. Knowing where the dust is and where it is headed in the solar system, for example, could help mitigate hazards for future human exploration, including dust particles damaging spacecraft or harming astronauts.