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Science 16 April 2004:
Vol. 304. no. 5669, pp. 395 - 396
DOI: 10.1126/science.1097150
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Perspectives

Also see the archival list of Science's Compass: Enhanced Perspectives

ATMOSPHERIC SCIENCE:
Enhanced: An Iron Deficiency in Polar Mesospheric Clouds

Donald M. Hunten

More than a century ago, observers noted the appearance of luminous high-altitude clouds at northern latitudes. These noctilucent clouds are now known to be ice crystals in the mesospheric region of the atmosphere. In his Perspective, Hunten discusses work reported in the same issue by Plane et al. on an unusual phenomenon in these polar mesospheric clouds. Normally, a layer of iron atoms from disintegrating meteorites is observed with laser spectroscopy in the mesosphere. But in the presence of polar mesospheric clouds, the iron atoms stick to the ice crystals and are missing from the spectroscopic signal. Such an effect may turn out to occur with other metal species in the atmosphere as well.

The author is at the Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA E-mail: dhunten{at}lpl.arizona.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)