The space probe Deep Impact will attempt to make history this weekend by blasting a crater into Comet Tempel 1. Scientists expect the crater - perhaps as large as a football field - will provide them a glimpse of fresh material uncovered by the impact. While comets are plentiful in our solar system, scientists know surprisingly little about their composition or internal structure. Comets are believed to be relatively pristine remnants of the creation of our solar system and have been implicated as a possible source for the water and organic material that became the building blocks for life on our planet.
About 24 hours before closest approach, Deep Impact will deploy a coffee table-sized impactor in the path of the comet. Deep Impact will then adjust its own trajectory to observe the impact from a safe distance. Traveling at over 37,000 kilometers per hour (23,000 miles per hour) Tempel 1 will quickly overtake the tiny impactor, resulting in celestial fireworks around 10:52 p.m. Pacific Daylight Time on Sunday, July 03, 2005. Tempel 1 is about the size of the island of Manhattan in New York, USA.
Cameras and other instruments onboard both Deep Impact and the impactor will observe the event, with the impactor expected to send images right up until its collision with the comet. Telescopes around the world, including some in orbit, will also be trained on the comet, allowing unprecedented coverage of the event. The first images could be made available in a briefing and press conference the following day.
Scientists are not sure whether or not the impact will be visible to the naked eye, but various amateur astronomy clubs, planetariums, universities and other groups plan to set up telescopes for public viewing of the event. A network of amateur astronomers has been organized to provide even more data prior to, during and after impact. In the United States, locations west of the Mississippi River under clear skies should have a good view of the comet. Looking to the southwest, Comet Tempel 1 will be visible slightly above and to the left of the star Spica and the planet Jupiter. Sky and Telescope has kindly provided the viewing illustrations provided in this article.
Several events are planned in the days following impact, including a presentation of science results at the University of Arizona on Saturday, July 09, 2005. The Frontier Channel will provide more information about Deep Impact mission results as it becomes available, including full coverage of the University of Arizona presentation.
In the past twenty years there have been only a handful of successful space probe missions to comets. NASA’s Stardust is expected to return material from Comet Wild 2 to the Earth in January 2006 and the ESA’s Rosetta will attempt to deliver the first lander on a comet to Comet 67P/Churyumov-Gerasimenko at the end of 2014.
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