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LOS ANGELES — A spacecraft that gave scientists their first peek into a comet's icy interior will explore no more, NASA said Friday.
The space agency declared an end to the Deep Impact spacecraft after it unexpectedly fell silent. Engineers tried for a month to regain contact, but lost hope.
Mission scientist Jessica Sunshine of the University of Maryland said she was "saddened at the loss of an old friend."
Deep Impact put on a celestial fireworks display July 4, 2005, when it fired a projectile into comet Tempel 1. The high-speed impact carved a crater and hurled a plume of debris into space, giving scientists their first glimpse of the comet's frozen primordial ingredients.
Afterward, Deep Impact journeyed toward comet Hartley 2, flying through a blizzard of ice particles and escaping unharmed. It later flew by the distant comet Garradd and also observed stars in search of Earth-sized planets outside the solar system.
Before Deep Impact lost contact last month, it was studying another comet named Ison that could shine as bright as the moon when it makes a close swing by Earth in November.
The cause of the failure was unknown, but engineers suspect the spacecraft lost control, causing its antenna and solar panels to point in the wrong direction. Without power flowing to its onboard computer, Deep Impact likely froze to death.
Scientists were disappointed at the timing of the silence that cut short their observations of comet Ison and future plans.
"It is hard to say goodbye," said mission scientist Lori Feaga of the University of Maryland.
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Comet ISON (C/2012 S1) may become a dazzling sight as it traverses the inner solar system in late 2013. During the weeks before its Nov. 28 close approach to the sun, the comet will be observable with small telescopes, and binoculars. Observatories around the world and in space will track the comet during its scorching trek around the sun. If ISON survives its searing solar passage, which seems likely but is not certain, the comet may be visible to the unaided eye in the pre-dawn sky during December.
This animation shows two views of comet ISON's path through the inner solar system. The first is a view following the comet along its orbit. The second is a view perpendicular to ISON's orbit.
Like all comets, ISON is a clump of frozen gases mixed with dust. Often described as "dirty snowballs," comets emit gas and dust whenever they venture near enough to the sun that the icy material transforms from a solid to gas, a process called sublimation. Jets powered by sublimating ice also release dust, which reflects sunlight and brightens the comet.
On Oct. 1, ISON passes within about 6.5 million miles (10.5 million km) of Mars. As it goes by, it may be visible to some of NASA's Mars rovers and satellites, including the Mars Reconnaissance Orbiter and Curiosity.
Then, on Nov. 28, ISON will make a sweltering passage around the sun. The comet will approach within about 730,000 miles (1.2 million km) of its visible surface, which classifies ISON as a sungrazing comet. In late November, its icy material will furiously sublimate and release torrents of dust as the surface erodes under the sun's fierce heat, all as sun-monitoring satellites look on. Around this time, the comet may become bright enough to glimpse just by holding up a hand to block the sun's glare.
Sungrazing comets often shed large fragments or even completely disrupt following close encounters with the sun, but for ISON neither fate is a forgone conclusion. Whatever happens, scientists will be able to learn more about comets by how it interacts with the sun's tenuous atmosphere, the corona.
Following ISON's solar swingby, the comet will depart the sun and move toward Earth, appearing in morning twilight through December. The comet will swing past Earth on Dec. 26, approaching within 39.9 million miles (64.2 million km) or about 167 times farther than the moon.
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Slooh.com's Canary Islands Observatory captured asteroid 433 Eros seeming to fly with Comet ISON on September 24th, 2013. This 2nd largest near-Earth asteroid -- which has been visited by the NEAR probe -- is traveling faster, along a different orb
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