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Close Encounters of the Comet KindComets are some of the most spectacular and eye-catching objects in our solar system. And they're no strangers to visitors from Earth … robotic ones, that is.
A veritable fleet of unmanned spacecraft have been launched to different comets over the years to see famed icy wanderers like Halley's Comet or Tempel 1 (which NASA visited with two different probes) up close and personal.
Take a look at the best close encounters of the comet kind in this short history of unmanned cometary exploration.
Updated Sept. 28, 2016.
Comet Giacobini-ZinnerSlide 2 of 18
Comet Giacobini-ZinnerThe first spacecraft to visit a comet was the International Cometary Explorer, which zipped through the tail of Comet Giacobini-Zinner in September 1985. ICE was originally launched in 1978, as part of the International Sun-Earth Explorer mission to study Earth's magnetosphere and its interaction with the solar wind.Slide 3 of 18
Halley's CometSlide 4 of 18
Halley's CometThe famed Halley's Comet was the first comet a spacecraft imaged up close. In 1986, the ESA's Giotto probe zoomed to within about 372 miles (600 km) of the icy wanderer's nucleus. Four other spacecraft also visited Halley that year — two each from the Soviet Union and Japan — but none approached as close as Giotto, according to NASA.
Giotto returned a lot of useful information, finding that the comet's nucleus is rough, porous, dark and dusty. The probe's data also helped scientists determine that Halley is made of some of the oldest stuff in the solar system, volatiles that condensed onto dust particles about 4.5 billion years ago.
Halley is about 9 miles (15 km) long by 5 miles (8 km) wide or so. It completes a circuit around the sun every 75 or 76 years. It should return to the inner solar system around 2061.Slide 5 of 18
Comet BorrellySlide 6 of 18
Comet BorrellyNASA's Deep Space 1 probe flew to within 1,364 miles (2,200 km) of Comet Borrelly in September 2001. The spacecraft returned dazzling and surprising photos, showing rolling, pitted terrain marked by grand mesas.
Deep Space 1's pictures of the potato-shaped Borrelly were hailed by scientists as the best yet taken of a comet. These images showed that Borrelly is even darker than Halley, reflecting just half as much light as the surface of the moon.
Comet Borrelly is about 5 miles (8 km) long and makes a complete trip around the sun once every 6.9 years.Slide 7 of 18
Comet Wild 2Slide 8 of 18