The moon’s airless atmosphere is layered by a moving cloud of tiny dust particles, to the surprise of NASA scientists.
Data from a recent NASA mission exploring the moon’s atmosphere has revealed evidence of this new dust cloud, which likely originated as the moon was peppered with meteorites.
Diane Wooden from the NASA Ames Research Centre in California and her colleagues published their analyses in Nature Geoscience.
While it has already been reported that a permanent dust cloud surrounds our moon, the new study describes a second fluctuating dust cloud, dense enough to be visible through scattered sunlight, but remote and dynamic in its movement.
Each particle of nanodust in this newly described outer-cloud could measure less than 20 nanometres – that is, 20 billionths of a metre – a size estimate based on the way the dust particles move and interact with light.
The cloud was spotted by the Lunar Atmosphere and Dust Environment Explorer, or LADEE, which was launched by NASA in September 2013 to investigate the composition of the moon’s exosphere – the outermost part of its surrounding environment. (It was intentionally crashed into the moon in April 2014.)
On the orbiter, two telescopes were employed to investigate the exosphere in the direction away from the sun, hunting for clues of a “sodium tail” extending from the moon. But, according to the paper, the resulting data also “provided unexpected evidence of a tenuous dust component in the extended lunar exosphere”.
The researchers believe the dynamic dust particles are the result of the moon’s airless atmosphere colliding with objects in the space environment, such as comets or meteorites, and the way they move through the universe tells a very different story from the larger particles previously examined.
Importantly, they write, this external dust cloud could be mirrored on comparable celestial bodies: “The detection of this nanodust component in the lunar exosphere suggests that similar phenomena may be occurring at other airless bodies throughout the solar system.”