Presentation on theme: "FINE DUST IN THE LUNAR ENVIRONMENT The Third Moscow Solar System Symposium V.V. Shevchenko, A.A. Berezhnoy, E.A. Kozlova Sternberg Astronomical Institute,"— Presentation transcript:
FINE DUST IN THE LUNAR ENVIRONMENT The Third Moscow Solar System Symposium V.V. Shevchenko, A.A. Berezhnoy, E.A. Kozlova Sternberg Astronomical Institute, Moscow State University Space Research Institute Moscow, Russia October 8-12, 2012
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).
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).
Image of Surveyor 6 casting an 18-meter-long shadow with the sun just 8 degrees above the horizon. LROC NAC image M L. Credit: NASA/Goddard/Arizona State University western horizon
Surveyor’s Images of Horizon Glow The image was taken by the Surveyor 6 on November 24, 1967, one hour after sunset.
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 ~ 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.
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
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
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
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 ) dust particles in lunar environment. BUT:
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 Institute Moscow, Russia October 8-12, 2012
. There is no official definition of what size fraction constitutes "dust", some place the cutoff at less than micrometres in diameter. Regolith Particle Size-Frequency Distribution
ReinerCarrelDaniellMaury A M LM LM RM R SLOPE AVALANCHE DEPOSITS IN CRATERS LRO/LROC IMAGES
SLOPE AVALANCHE DEPOSITS IN CRATER MAURY Fine fraction (~ 5 ) seems to have played a major role in the creation of a high degree of fluidity of sloping flows.
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 ) dust particles in lunar environment
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 10 7 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
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