Halley's comet

"Comet Hale-Bopp Approaches: The Importance of Comets to Life on Earth" will be the theme for a free public lecture to be held at 7 p.m., Thursday, March 20, in JPL's von Krmn Auditorium, 4800 Oak Grove Drive, Pasadena. Seating is on a first-come, first-served basis.

Comets, composed of ice and dust, are believed to be the remnants of the birth of the solar system. Their primordial material may lend clues in learning more about the origin and evolution of the planets. Originating in a region from beyond the orbit of Pluto, comets can have orbits taking several thousand years to complete.

As comets draw closer to the Sun, their surface material begins to heat up and vaporize, creating the long tail of dust and gas that makes a comet visible to observers on Earth. Comet Hale-Bopp, named after co-discoverers Alan Hale and Thomas Bopp, is returning to orbit the Sun after 4,200 years. The comet is currently visible at dusk and just before dawn in the Northern Hemisphere, and will make its closest approach to Earth of about 122 million miles on March 22.

Several NASA missions are planned to further study the nature of comets. Stardust, scheduled for launch in 1999, will capture ejected materials from Comet Wild 2 in 2004 and return those samples to Earth in 2006. New Millennium Deep Space One, scheduled for launch in 1998, will fly by the asteroid named McAuliffe and Comet West-Kohoutek-Ikemura in a demonstration of new spacecraft technologies.

The lecture will be hosted by Dr. Don Yeomans, a senior research scientist in JPL's Solar System Dynamics Group. Yeomans has been studying comets for nearly three decades, and has also been active in planning space missions geared toward comet studies. He will lead a discussion of what can be expected of Comet Hale-Bopp as it brightens in the next several weeks.

For further information, contact the Public Information Office at (818) 354-5011.

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