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Comets

Bright Objects Keep Us In The Dark

In a pair of space missions planned for the early part of the twenty-first century, space probes will rendezvous with a pair of short-period comets, hopefully to help scientists reach a better understanding of the physics of comets. NASA's Stardust mission, launched in 1999, is on its way to capture dust from the tail of Comet Wild (pronounced "vilt") 2 in 2004, returning the samples to Earth in 2006 for analysis. In February 2003, the European Space Agency's Rosetta mission—originally scheduled to rendezvous with Comet Wirtanen on its trip around the Sun—was postponed due to launch failures suffered by Europe's Ariane 5 rocket. In March 2003, ESA scientists retasked the Rosetta mission spacecraft to rendezvous with 67P/Churyumov-Gerasimenko. With a launch planned as early as January 2004, Rosetta will orbit the comet and send a probe to the surface. An early 2004 launch date will permit a rendezvous in 2014. The larger size of 67P/Churyumov-Gerasimenko—and thus a stronger gravitational field—poses some problems for the lander that will require recalculation of the landing impact stress on the lander legs.

At present, however, despite spaceships probing the outer limits of our solar system; gigantic telescopes in deserts, atop mountains, and floating in space; and satellites designed specifically to capture meteor dust hurtling through Earth's atmosphere from interstellar space, significant questions about the origin, nature, and fate of comets remains unsolved.

Resources

Books

Bailey, M.E., S.V.M. Clube, and W.M. Napier. The Origin of Comets. Oxford: Pergamon Press, 1990.

Gibilisco, Stan. Comets, Meteors & Asteroids: How They Affect Earth. Blue Ridge Summit, PA: Tab Books, 1985.

Levy, David H. The Quest for Comets: An Explosive Trail of Beauty and Danger. New York: Plenum Press, 1994.

Yeomans, Donald K. Comets, A Chronological History of Observation, Science, Myth, and Folklore. New York: John Wiley & Sons, 1991.


Other

National Aeronautics and Space Administration. "STARDUST Mission." 2000. (cited October 19, 2002). <http://stardust.jpl.nasa.gov/mission/>.


Marie L. Thompson

KEY TERMS

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Coma

—Glowing cloud of mass surrounding the nucleus of a comet.

Ellipse

—An eccentric or elongated circle, or oval.

Ion

—An atom or molecule which has acquired electrical charge by either losing electrons (positively charged ion) or gaining electrons (negatively charged ion).

Nucleus

—Core, or center.

Parabola

—Open-ended, elongated ellipse; ushaped.

Perturbation

—Change in the orbit of an astronomical body by the gravitational influence of a body other than the one around which the object orbits.

Solar wind

—A stream of charged and neutral particles that emanates from the Sun and moves into the solar system.

Spectrograph

—Instrument for dispersing light into its spectrum of wavelengths then photographing that spectrum.

Additional topics

Science EncyclopediaScience & Philosophy: Cluster compound to ConcupiscenceComets - Age-old Fascination, Stargazing And Discovering Comets, Comets And Earth, Bright Objects Keep Us In The Dark - origin Composition and extinction