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Zusammenfassung

We suggest that Pluto and Charon are immersed in a tenuous dust cloud. The cloud consists of ejecta from Pluto and-especially- Charon, released from their surfaces by impacts of micrometeoroids originating from Edgeworth-Kuiper belt objects. The motion of the ejected grains is dominated by the gravity of Pluto and Charon, which determines a pear-shape of the densest part of the cloud. While the production rates of escaping particles from both sides are comparable, the lifetimes of the Charon particles inside the Hill sphere of Pluto-Charon with respect to the Sun are much longer than of the Pluto ejecta, so that the cloud is composed predominantly of Charon grains. The dust cloud is dense enough to be detected with an in situ dust detector onboard a future space mission to Pluto. The Cloud's maximum optical depth of tau approximate to 3 x 10(-11) is, however, too low to allow remote sensing observations. (C) 2002 Elsevier Science Ltd. All rights reserved.