2.2.4 Lunar Soil Movement Registered by the Apollo 17 Cosmic Dust Experiment

Berg, O. E.; Wolf, Hinko; Rhee, John W.

doi:10.1017/s0252921100051757

Cited by 37 publications

(47 citation statements)

References 1 publication

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“…The Lunar Ejecta and Meteorites (LEAM) experiment was deployed on the lunar surface during the Apollo 17 mission to monitor the cosmic dust influx. The signatures recorded by LEAM were unlikely to be caused by cosmic dust, but were consistent with the presence of high fluxes of slow-moving, highly charged lunar fines 7 . Stubbs et al 8 have previously reported a dust fountain model up to about 100 km altitude.…”

supporting

confidence: 64%

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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confidence: 64%

Levitation of Charged Dust Grains and its Implications in Lunar Environment

Pabari¹,

Banerjee²

2016

Current Science

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“…Additional information relating to the source of this phenomenon was obtained by the Apollo 17 Lunar Ejecta and Micrometeoroids (LEAM) surface experiment [e.g., Berg et al, 1976], which operated for several years. For several hundred hours around lunar sunrise (indeed, beginning as much as 150 hours prior), signals from LEAM were found to be dominated by a population of low-energy impacts.…”

Section: Suspended Dust In the Lunar Atmospherementioning

confidence: 99%

The lunar atmosphere: History, status, current problems, and context

Stern

1999

Reviews of Geophysics

337

284

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Abstract. After decades of speculation and fruitless searches by observers, the lunar atmosphere was first observed by Apollo surface and orbital instruments beginning in 1971. With the end of Apollo missions in 1972 and the termination of funding for Apollo lunar ground station observations in 1977 the field withered for many years, but it has recently enjoyed a renaissance. This renewal was initiated by the discovery of lunar atmospheric sodium and potassium by ground-based observers and was furthered by the in situ detection of metal ions derived from the Moon in interplanetary space, the possible discoveries of H20 ice at the poles of the Moon and Mercury, and the detection of tenuous atmospheres around other remote sites in the solar system, including Mercury and several Galilean satellites. In this review I attempt to summarize the present state of knowledge about the lunar atmosphere, describe the important physical processes taking place within it, and compare the lunar atmosphere with other tenuous atmospheres in the solar system. OVERVIEWOwing to the lack of optical phenomena associated with the lunar atmosphere, it is usually stated that the Moon has no atmosphere. This statement is not correct. In fact, the Moon is surrounded by a tenuous envelope with a surface number density and pressure not unlike that of a cometary coma. (See note 1 in the notes section following the main text.) Since the lunar atmosphere is in fact an exosphere (see note 2), one can think of its various compositional components as "independent atmospheres" occupying the same space. This review is structured as follows: In section 1 I will describe the history and provide an overview of the current state of knowledge about the lunar atmosphere. In section 2 I discuss the structure and dynamics of the lunar atmosphere. In section 3 1 provide a more detailed look at the production and loss mechanisms of the lunar atmosphere. In section 4 I provide a comparison of the lunar atmosphere to tenuous exospheres around other bodies in the solar system, with particular emphasis on comparison to Mercury. In section 5 I examine some special topics, including some comments on both the ancient lunar atmosphere and human influences that may occur in the future. Finally, in section 6, I summarize the major outstanding issues concerning lunar atmospheric science and briefly describe some important experiments that could shed more light on this tenuous but fascinating aspect of Earth's nearest neighbor.Before beginning, I caution the reader that this review could not possibly cover every topic relating to the lunar atmosphere in the depth it deserves, and tough choices had to be made about both the breadth and depth of the discussions that follow. Any deficiencies in this approach are the responsibility of this author. A Brief Pre-Apollo History of Quantitative Atmospheric SearchesAlthough the lunar atmosphere was not detected until the Apollo era, scientifically based searches for it extend back to telescopic observations by Galileo. Based on the...

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“…Figure 4.14 shows the rates recorded by the LEAM sensors per 3-hour interval as reported by Grün and Horányi [33]. In the previous studies [15,16,64], the explanation was given, that LEAM was registering slowly moving (< 100 m·s −1 ) lunar dust particles with surface charges above 1 pC, triggered by the sunrise/sunset levitation and transport phenomena. Assuming a daytime surface potential of +5 V, the measurements indicate grains sizes of the order of a millimeter in radius.…”

Section: Ejecta As An Explanation For Leam Datamentioning

confidence: 78%

“…The pressures are highest in the impact point zone, and the materials ejected near the impact point are therefore dominated by small fragments with high speeds and shallow ejecta angles with respect to the target surface. These impact ejecta grains can be observed by a dust sensor located on the lunar surface [16,56].…”

Section: Lunar Dust Sources 421 Lunar Impact Ejecta Environmentmentioning

confidence: 99%