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FINE DUST IN THE LUNAR ENVIRONMENT
The Third Moscow Solar System Symposium
V.V. Shevchenko, A.A. Berezhnoy, E.A. KozlovaSternberg Astronomical Institute, Moscow State University
Space Research InstituteMoscow, RussiaOctober 8-12, 2012
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Surveyor’s Images of Horizon Glow
Surveyors 5, 6, and 7 captured the first evidence of dust transport on airless bodies with their television cameras.View of horizon approximately 15 minutes after
local sunset (Courtesy NASA/JPL).
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Surveyor’s Images of Horizon Glow
Just after sunset, a horizon glow was observed above the western horizon. This was interpreted to be forward scattered light from a cloud
of dust particles with radii ~5 μm, vertical dimension ~3-30 cm, and horizontal dimension ~14 m.
View of illumination along horizon approximately 90 minutes after local sunset (Courtesy NASA/JPL).
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Image of Surveyor 6 casting an 18-meter-long shadow with the sun just 8 degrees above the horizon. LROC NAC image M117501284L.
Credit: NASA/Goddard/Arizona State University
western horizon
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Surveyor’s Images of Horizon Glow
The image was taken by the Surveyor 6 on November 24, 1967, one hour after sunset.
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Modeling Dust Clouds on the Moon
POSITION OF THE SOLAR DISK
western horizon
Surveyor’s images of horizon glow
These observations were interpreted to be forward scattered light from a cloud of dust particles with radii ~ 5 µm, vertical dimension ~ 3-30 cm, and horizontal dimension ~14 m, , and
about 50 grains on cm–2 (Szalay and Horanyi, 2012).
The very small size of particles is an important condition of existence of a horizontal levitation of a lunar dust.
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In the morning, the storm raging on the Moon Apollo 17, 1972
This is evidenced by the results of the data obtained with the instrument LEAM (Lunar Ejecta and Meteorites).Credit: NASA
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This is a sketch of the lunar sunrise seen from orbit by Apollo 17 astronaut Eugene Cernan. On the right, the sketch is highlighted to show the sources of the scattered light: red indicates Coronal
and Zodiacal Glow, blue is the Lunar Horizon Glow, perhaps caused by exospheric dust, and green indicates possible "streamers" of
light (crepuscular rays) formed by shadowing and scattered light. Credit: NASA
ORBITAL OBSERVATIONS
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This is a picture of coronal and zodiacal light (CZL) taken with the Clementine spacecraft (1994), when the Sun was behind
the Moon. The white area on the edge of the Moon is the CZL, and the bright dot at the top is the planet Venus. Credit: NASA
ORBITAL OBSERVATIONS
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Rocks not coated with dust.Laser reflectors continue to operate 35 years later.
So, it’s needed to find the origin of very fine (~ 5 m) dust particles
in lunar environment.
BUT:
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POSSIBLE ORIGIN OF THE FINE DUST
IN LUNAR EXOSPHERE
The Third Moscow Solar System Symposium
V.V. Shevchenko Sternberg Astronomical Institute, Moscow State University
Space Research InstituteMoscow, RussiaOctober 8-12, 2012
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. There is no official definition of what size fraction constitutes "dust", some place the cutoff at less than 50 - 70 micrometres in diameter.
Regolith Particle Size-Frequency Distribution
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Reiner Carrel Daniell Maury A
M109569228L
M111422761L M106676014R M108964159R
SLOPE AVALANCHE DEPOSITS IN CRATERS
LRO/LROC IMAGES
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SLOPE AVALANCHE DEPOSITS IN CRATER MAURY
Fine fraction (~ 5 m) seems to have played a major role in the creation of a high degree of fluidity of sloping
flows.
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The area of “failure” in the northeastern wall of crater Diophantus is located at a depth of 290 to 640 m.
Area of “failure” is source of very fine (~ 5 m) dust particles in lunar environment
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Electrically charged grains could be levitated into the cloud by intense electrostatic fields (> 500 V cm–1) extending across the sunlight/shadow boundaries.
Detailed analysis of the HG absolute luminance, temporal decay, and morphology confirm the cloud
model. The levitation mechanism must eject 107 more particles per unit time into the cloud than could micro
meteorites. Electrostatic transport is probably the dominant local transport mechanism of lunar surface
fines (Rennilson and Criswell, 1973) .
Levitation mechanism
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One of unsolved problems of sloping movement of substance is to understand the causes for the existence of the fine faction
of regolith at a depth of hundreds of meters
KAGUYA SUBSURFACE DATA
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