Evidence for a Dynamic Nanodust Cloud Enveloping the Moon

Wooden, D. H.; Cook, A. M.; Colaprete, A.; Glenar, D. A.; Stubbs, T. J.; Shirley, M.

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NASA NTRS · 20170002391

Evidence for a Dynamic Nanodust Cloud Enveloping the Moon

Wooden, D. H.·Cook, A. M.·Colaprete, A.·Glenar, D. A.·Stubbs, T. J.·Shirley, M.

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Abstract

The exospheres that surround airless bodies such as the Moon are tenuous, atmosphere-like layers whose constituent particles rarely collide with one another. Some particles contained within such exospheres are the product of direct interactions between airless bodies and the space environment, and offer insights into space weathering processes. NASAs Lunar Atmosphere and Dust Environment Explorer (LADEE) mission studied the Moons exospheric constituents in situ and detected a permanent dust exosphere1 of particles with radii as small as 300 nm. Here we present evidence from LADEE spectral data for an additional fluctuating nanodust exosphere at the Moon containing a population of particles sufficiently dense to be detectable via scattered sunlight. We compare two anti-Sun spectral observations: one near the peak of the Quadrantidmeteoroid stream, the other during a period of comparativelyweak stream activity. The former shows a negative spectralslope consistent with backscattering of sunlight by nanodustgrains with radii less than 20 to 30 nm; the latter has a flatterspectral slope. We hypothesize that a spatially and temporallyvariable nanodust exosphere may exist at the Moon, and thatit is modulated by changes in meteoroid impact rates, suchas during encounters with meteoroid streams. The findingssuggest that similar nanodust exospheresand the particle ejection and transport processes that form themmay occurat other airless bodies.

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Wooden, D. H., Cook, A. M., Colaprete, A., Glenar, D. A., Stubbs, T. J., Shirley, M.. 2015-08-15. Evidence for a Dynamic Nanodust Cloud Enveloping the Moon. https://ntrs.nasa.gov/citations/20170002391

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