WASHINGTON - Scientists are preparing for the launch July 1 of a new spacecraft designed to fly as close as 60 miles to the icy cores of two approaching comets - and perhaps provide clues to the origins of life on Earth.
If it works, the $159 million Contour mission would provide scientists with their closest look at two very different types of comets. The first encounter is set for late next year.
Contour (for Comet Nucleus Tour) was built at the Johns Hopkins University's Applied Physics Lab, and the mission will be run from the APL's Laurel campus.
"Comets are the solar system's smallest bodies but among its biggest mysteries," said Cornell University astronomer Joseph Veverka, the mission's principal investigator. "We believe they hold the most primitive materials in the solar system and that they played a role in shaping some of the planets. But we really have more ideas about comets than facts."
Contour is set for launch just before 3 a.m. July 1, from the Cape Canaveral Air Force Station in Florida. After 45 days in Earth orbit, it will fire its rocket and set off for a Nov. 12, 2003, rendezvous with comet Encke. Its second encounter, with comet Schwassmann-Wachmann 3, is expected in June 2006.
Comets have a small nucleus of ice and rock, surrounded by a large, glowing halo of dust and gas, which the sun's radiation often sweeps into a characteristic "tail."
Many scientists believe that a rain of comets soon after the solar system formed might have been the source of much of the water, atmosphere and organic compounds that made life possible on Earth.
In more recent epochs, they say, comet impacts may well have changed the course of evolution by triggering extinctions among some species while providing opportunities for others.
"If it were not for comets, we would quite likely not be here," said Donald K. Yeomans of NASA's Jet Propulsion Laboratory, a co-investigator on the mission's science team.
Spacecraft from Earth have visited comets several times before, beginning in 1985. Last year, NASA's Deep Space 1 mission passed just 1,349 miles from comet Borelly. The Deep Impact mission, led by University of Maryland astronomer Michael A'Hearn, will hurl a 771-pound copper projectile at comet Tempel I in 2005.
The 1-ton Contour was designed for reliability and low cost. Its solar panels and antennas are fixed, so they don't need to unfold or deploy after launch.
