Evidence for a dynamic nanodust cloud enveloping the Moon

Absence of a detectable lunar nanodust exosphere during a search with LRO's LAMP UV imaging spectrograph

“…Dust upper limits for the six sets of LAMP observations, computed for r gr ≈ 25 nm (consistent with the grain radii inferred from the LADEE/UVS observations [ Wooden et al, ]). (a) Spectra for each observation along a fully illuminated LOS were binned into 2 nm spectral intervals (black lines).…”

“…The solar elongation angle, i.e., the angle between the LAMP‐Sun direction and the LAMP‐target direction, was 143°, so any dust detection would arise from the backscattering of sunlight by dust grains. This figure is particularly useful when compared with Figure 1 in Wooden et al [] to highlight the geometric differences between the LADEE/UVS observations and the LRO/LAMP ones described here. One distinction between these two data sets is the region of the lunar dust exosphere being sampled.…”

“…This broadband signal was not evident in observations under similar viewing conditions on 10 April 2014, which coincided with weak meteoroid stream activity. Therefore, Wooden et al [] hypothesized that these observations were consistent with a spatially and temporally variable nanodust exosphere modulated by changes in meteoroid impact rates, as occurs during meteoroid streams when the Moon encounters a debris trail from either a comet or asteroid [ Stubbs et al , ; Horányi et al , ; Szalay and Horányi , ]. (On Earth such encounters are typically observed as meteor showers [ Jenniskens , ].)…”

“…Since the path along the LADEE/UVS line of sight (LOS) was partially shadowed during the observations, with shadow lengths up to several thousand kilometers, the nanodust population would have to extend very far from the Moon in order to be detectable via scattered sunlight. In fact, during the QUA meteoroid stream, Wooden et al [] inferred the greatest nanodust column abundances early in the observing activity when the shadow lengths were at their longest. The abundance of nanodust inferred by LADEE/UVS was at least 4 orders of magnitude greater than would be predicted by extrapolating the ejecta mass distribution in the Krivov et al [] impact‐generated dust cloud model to smaller grains, suggesting that this model may not be suitable for describing nanodust ejecta in near‐lunar space.…”

In Situ Measurements of Lunar Dust at the Chang'E‐3 Landing Site in the Northern Mare Imbrium

“…Thus, in order to mitigate the lunar dust‐related problems, provide substantial guidance for the planning of future lunar exploration even extraterrestrial settlement constructions, and offer valuable information for understanding lunar atmospheric evolution, in situ measurement of dust deposition on the lunar surface is the first step for achieving these purposes. To date, however, the reports about in situ measurements of dust on the lunar near surface are comparatively few (Berg et al, ; Grün & Horányi, ; O'Brien, ) even though some studies were executed from lunar orbits (Feldman et al, ; Glenar et al, ; Grava et al, ; Horányi et al, ; Szalay & Horányi, ; Wooden et al, ). On 14 December 2013 at 21:11 (UTC + 8), Chang'E‐3 (CE‐3) spacecraft, the first visitor from China soft‐landing on the Moon surface, successfully touched down at 44.12°N, 19.51°W on the Moon (Fa et al, )—a region that was neglected by previous expeditions, which carried, among other instruments, one lunar dust detector (LDD), providing an unique opportunity to learn about the lunar dust deposition in the northern Mare Imbrium.…”