The NASA Deep Impact spacecraft maneuvered as close as 435 miles to Comet Hartley 2 Thursday and beamed back close-up images from deep space. The Deep Impact spacecraft completed a similar rendezvous in 2005 with Comet Tempel 1. Australian astronomer Malcolm Hartley was present at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., when the first images arrived from the comet he discovered in 1986.
Deep space encounter
When NASA’s Deep Impact spacecraft beamed back the first photos from its rendezvous with Comet Hartley 2, scientists standing by at JPL Labs cheered and applauded. The comet nucleus, about three quarters of a mile across, looked like a misshapen ball of cosmic ice resembling a chicken drumstick emitting glowing jets of dust and gas as it hurtled through space. After traveling 2.5 billion miles in five years, the spacecraft flew past the Comet Hartley 2 at a speed of more than seven miles per second, or 27,000 mph.
NASA’s Deep Impact mission
Scientists study comets because they harbor original ingredients from the formation of the solar system about 4.5 billion years ago. The NASA Deep Impact mission launched in January 2005 visited Comet Tempel 1. When it arrived at the comet it launched an 800-pound copper projectile into the nucleus. On impact a plume of ice and dust was measured by sensors to identify the composition of the comet. Deep Impact was then sent to rendezvous with Comet Boethin in 2008, but that comet broke up and disappeared when the spacecraft was en route. It was rerouted to Hartley 2, which took another two years to reach.
NASA deep space missions
Comet Hartley 2 is the fifth comet to be photographed by deep space probes. The other four are Halley, Wild 2, Borelli and Tempel 1. Each comet looks radically different from the others. Stardust, another NASA comet spacecraft, passed by Comet Wild 2 in 2006 and captured grains of dust from its tail. Later it sent the dust in a capsule back to Earth and moved on for another rendezvous with the target of Deep Impact’s first mission, Tempel 1, on Valentines Day 2011.