On the horizon: Clementine probes moon glow.Astronauts orbiting the moon aboard Apollo 17 in 1972 viewed two features of our solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. normally washed out by the sun's glare. Each time the solar disk rose from behind the moon, the crew witnessed the faint illumination from the sun's outer atmosphere, or corona, as well as the dim glow of zodiacal light zodiacal light or zodiacal band, a faint band of light sometimes seen in the western sky just after sunset in the spring, extending up from the horizon at the point where the sun has just set, or in the eastern sky just before sunrise in the - sunlight scattered by interplanetary dust. Using sketchpads, the crew drew what they saw just before the sun began poking out from behind the cratered lunar surface. Their drawings, researchers later realized, show more than just the corona and zodiacal light. Near the limb of the moon, the sketches reveal the strange phenomenon of horizon glow, caused by the scattering of light from gas or dust suspended several kilometers above the moon. This puzzled researchers because they thought the moon's negligible atmosphere lacked the material to create a glow. Two decades after Apollo, the Clementine Clementine forty-niner’s drowned daughter; “lost and gone forever.” [Am. Music: Leach, 236] See : Grief spacecraft appears to have photographed the horizon glow. At the Lunar and Planetary Science Conference The Lunar and Planetary Science Conference (LPSC), jointly sponsored by the Lunar and Planetary Institute (LPI) and NASA Johnson Space Center (JSC), brings together international specialists in petrology, geochemistry, geophysics, and astronomy to present the latest results of in Houston last week, Eugene M. Shoemaker reported that the craft - now midway through its 2-month survey of the moon - may have captured the glow in an image taken by one of its star-tracker cameras. Shoemaker, a Clementine scientist based in Flagstaff Flagstaff, city (1990 pop. 45,857), seat of Coconino co., N Ariz., near the San Francisco Peaks; inc. 1894. Lumbering, ranching, and a lively tourist trade thrive in the region, where many ruined pueblos, numerous state parks, several lakes, and large pine forests , Ariz., says a higher-resolution camera on board could verify the glow. Herbert A. Zook of NASA's Johnson Space Center (JSC JSC Johnson Space Center (NASA) JSC Joint Stock Company JSC Java Studio Creator JSC Joint Steering Committee JSC Joint Standing Committee JSC Journal of Symbolic Computation JSC Joint Scientific Committee ) in Houston says his analysis of the star-tracker image, conducted with JSC colleague Andrew E. Potter, indicates "an 80 percent likelihood" that Clementine recorded the horizon glow. To explain the glow, Zook says he favors a model proposed by David R. Criswell of the University of Houston. In that model, sunlight striking the moon strips atoms of their electrons. Both the ionized i·on·ize tr. & intr.v. i·on·ized, i·on·iz·ing, i·on·iz·es To convert or be converted totally or partially into ions. i atoms and the electrons would then impart a charge to lunar dust particles. The charged dust would rise several kilometers above the moon, creating the horizon glow by scattering light. But Zook adds that the glow remains a mystery "that researchers don't pretend to fully understand." |
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