for National Geographic News
NASA's Deep Impact spacecraft will be launching a projectile into the surface of comet Tempel 1 on Monday, possibly causing the most spectacular fireworks on U.S. Independence Day.
"The time of comet encounter is near, and the major mission milestones are getting closer and closer together," said Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, California. "After all the years of design, training and simulations, we are where we want to be. The flight and science teams are working the mission plan, and we are good to go for encounter," he added.
The flyby spacecraft will use medium- and high-resolution imagers and an infrared spectrometer to collect and send to Earth pictures and spectra of the event. Also watching Deep Impact will be NASA's Hubble and Spitzer space telescopes, the Chandra X-ray Observatory, the Swift and Submillimeter Wave Astronomy satellites, and the European Space Agency's XMM-Newton X-ray observatory and Rosetta spacecraft.
Observatories on Earth will view the impact and its aftermath.
"Those in the U.S. living west of the Mississippi [and in] Hawaii, and [those living in] New Zealand will have ringside seating for the impact event in a dark sky," said Don Yeomans, a Deep Impact mission scientist at JPL.
Scientists, who know very little about the interior of comets, hope the trash can-size projectile will smash a hole deep enough in the comet's icy exterior to reveal what lies inside it.
Learning more about what comets are made of will help explain the role they played in forming our solar system. Many scientists consider comets to be the source of most of the water and organic material that was once delivered to all terrestrial planets.
"The mission will help us understand the earliest phases of the solar system by learning what's really inside a comet in its pristine form," said Jay Melosh, a professor of planetary science at the University of Arizona in Tucson. Melosh is also a member of the Deep Impact science team.
The experiment could also help scientists devise ways to deflect rogue comets if they threaten to collide with Earth in the future.
During the early morning hours of July 3, a flyby spacecraft will deploy a 39-inch-wide (1-meter-wide), copper-fortified probe into the path of Tempel 1. The comet is about half the size of Manhattan and is hurtling through space at 23,000 miles an hour (37,000 kilometers an hour).