A permanent, asymmetric dust cloud around the Moon

Horányi, M.; Szalay, J. R.; Kempf, S.; Schmidt, Jürgen; Grün, E.; Srama, R.; Sternovsky, Z.

doi:10.1038/nature14479

Cited by 211 publications

(170 citation statements)

References 30 publications

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“…The LDEX instrument was capable of detecting grains with radii a ≥0.3μm at the LADEE orbital speed of 1.6–1.7 km/s. LDEX measurements revealed a permanently present, asymmetric dust cloud engulfing the Moon (Horányi et al, ), with a large density enhancement on the lunar apex hemisphere (in the direction of orbital motion). These measurements also determined the size distribution, where the ejecta exhibited a consistent power law for particles as small as a = 0.3μm.…”

Section: Ejecta Model Descriptionmentioning

confidence: 99%

“…Following the previous empirical fit to the lunar dust cloud (Szalay & Horányi, ), where M + is directly proportional to the density of ejecta at the surface. The density n (m −3 ) as a function of altitude h (km), local time ϕ , latitude λ , and particle radius a μ (μm) is then given by

n false(h, ϕ, λ, a false) = e^{- h false/ h_{0}} a_{μ}^{- q} n_{w} \sum_{s} w_{s} \cos^{3} false(normalΔ φ_{s} false) normalΘ false(false| normalΔ φ_{s} false| - π false/ 2 false),

where h 0 =200 km, q = 2.7 (Horányi et al, ), n w is a normalization density (m −3 ) that is scaled to be consistent with LDEX measurements, s is the index for the sources, w s is the relative weight of each source where

\sum_{s} w_{s} = 1

normalΔ φ_{s} = \cos^{- 1} false[\cos ϕ {\cos ϕ}_{s} + \sin ϕ {\sin ϕ}_{s} \cos false(ϕ {- ϕ}_{s} false) false]

is the angle to a given source, and Θ is the Heaviside function. The additional

\cos φ

in the

\cos^{3} φ

is from the surface area projection of the flux.…”

Section: Ejecta Model Descriptionmentioning

confidence: 99%

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Impact Ejecta and Gardening in the Lunar Polar Regions

et al. 2019

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The Moon is continually bombarded by interplanetary meteoroids. While many of the meteoroid sources are near the ecliptic plane, a significant population of high‐inclination meteoroids exists at 1 au that bombards the lunar polar regions. Building on previous measurements of the response of the lunar impact ejecta cloud to known meteoroid sources, we develop an ejecta model for the entire lunar surface by incorporating the high‐inclination sources. We find that the polar regions of the Moon experience similar quantities of impact ejecta production as the equator. Due to the enhanced impactor fluxes near the equator and at high latitudes on the dawn side, lunar regolith is preferentially distributed to the mid to high‐latitude regions over long timescales, providing a pathway to mix regolith from different regions. We find impact ejecta yields at the Moon to be significantly lower than the Galilean moons, suggesting meteoroids deliver more energy to the local regolith and can be an important driver in the evolution of volatiles near the lunar surface. Additionally, we find that a polar orbiting spacecraft equipped with a dust analyzer can measure appreciable quantities of lunar ejecta near the poles to constrain the water content in the polar regions.

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Section: Ejecta Model Descriptionmentioning

confidence: 99%

n false(h, ϕ, λ, a false) = e^{- h false/ h_{0}} a_{μ}^{- q} n_{w} \sum_{s} w_{s} \cos^{3} false(normalΔ φ_{s} false) normalΘ false(false| normalΔ φ_{s} false| - π false/ 2 false),

\sum_{s} w_{s} = 1

normalΔ φ_{s} = \cos^{- 1} false[\cos ϕ {\cos ϕ}_{s} + \sin ϕ {\sin ϕ}_{s} \cos false(ϕ {- ϕ}_{s} false) false]

is the angle to a given source, and Θ is the Heaviside function. The additional

\cos φ

in the

\cos^{3} φ

is from the surface area projection of the flux.…”

Section: Ejecta Model Descriptionmentioning

confidence: 99%

Impact Ejecta and Gardening in the Lunar Polar Regions

et al. 2019

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“…Based on the latest data, the Lunar Dust EXperiment (LDEX) sensor onboard lunar orbiter Lunar Atmosphere and Dust Environment Explorer (LADEE) already identified the existence of a dust cloud around the lunar surface down to 5 km [47].…”

Section: Lunar Dust Sources 421 Lunar Impact Ejecta Environmentmentioning

confidence: 99%

Instrument study of the Lunar Dust eXplorer (LDX) for a lunar lander mission

Srama

Henkel

et al. 2014

Advances in Space Research

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“…Results from the lunar dust experiment on LADEE mission suggest the presence of a permanent, asymmetric dust cloud around the Moon, formed by impacts of high-speed cometary dust particles on eccentric orbits, in contrast to particles of asteroidal origin striking the Moon at lower speeds 17 . Horanyi et al 18 have reported a permanent asymmetric dust cloud around the Moon and have found that the density distribution exhibits a strong enhancement near the morning terminator. They reported that the observation suggests the spatial and velocity distributions of the interplanetary dust particles which generate the ejecta clouds.…”

mentioning

confidence: 99%

“…They reported that the observation suggests the spatial and velocity distributions of the interplanetary dust particles which generate the ejecta clouds. Also, Horanyi et al 18 mentioned that the LDEX dust current measurements remained independent of altitude and hence gave no indication of the relatively dense cloud of 0.1 m sized dust that was inferred from the Apollo observations over the lunar terminator. Thus, dust levitation has not been confirmed till date and this communication presents a study using electrostatic modelling of dust levitation and discusses its implications in lunar environment.…”

mentioning

confidence: 99%

Levitation of Charged Dust Grains and its Implications in Lunar Environment

Pabari¹,

Banerjee²

2016

Current Science

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The surfaces of airless, non-magnetized bodies like the Moon are directly exposed to solar wind and ultraviolet radiation, causing surface dust grains to be electrically charged and levitated, whenever electric fields exceed the surface forces and gravity. For an improved understanding of the lunar dust environment, we study the surface charging processes using electrostatic modelling and present the results here. We apply Gauss's law to examine the dust levitation and compare the implications with those obtained using freespace capacitance of the particle. Calculating grain charge on surface by assuming its free-space capacitance is erroneous and is therefore inapplicable. The daytime surface potential during high solar activity is estimated to be ~20 V, while the nighttime potential can be as high as -3.8 kV. The maximum radius of levitating particles is greatly affected by the method used to model the dust levitation. Using Gauss's approach, it comes out to be in the picometre range near the terminator, in contrast to existing calculations which estimate it to be in the nanometre to micrometer range. The LDEX provided no indication of 0.1 m-sized particles near the terminator, as suggested previously from Apollo observations. This result is not inconsistent with our predictions based on Gauss's law. Hence, it still remains an open question whether dust levitation occurs on the Moon or not, and experiments are necessary on future lunar lander mission which provide direct measurement of surface potential and near-surface charged dust particles to confirm the same.

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A permanent, asymmetric dust cloud around the Moon

Cited by 211 publications

References 30 publications

Impact Ejecta and Gardening in the Lunar Polar Regions

Impact Ejecta and Gardening in the Lunar Polar Regions

Instrument study of the Lunar Dust eXplorer (LDX) for a lunar lander mission

Levitation of Charged Dust Grains and its Implications in Lunar Environment

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