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Comets have been known since antiquity. Often described as dirty snowballs and icy mudballs, comets are water ice and frozen gases mixed with dust samples from the earliest history of our Solar System.
ISEE-3/ICE made the first-ever comet encounter in 1985 [NASA art]
Nearly 900 comets have been cataloged over the years. Of those, 184 are listed as periodic comets which circle the Sun every so often, up to at least once every 200 years.
Most comets are in highly eccentric orbits, which take them around the Sun and out beyond the orbit of the planet Pluto. Such long-period comets usually are seen once and then disappear for thousands of years. On the other hand, short-period and intermediate-period comets like Comet Halley stay within the orbit of Pluto for most of their orbits.
After it swings in through the inner Solar System and around the Sun a few hundred times, most of a comet's ice and gas will have been lost. It is left as a rocky object looking very much like an asteroid. In fact, some astronomers say half of the so-called near-Earth asteroids may be "dead" comets.
A comet in an orbit near the Sun might crash into one of the planets or even the Sun itself. On the other hand, the powerful gravitational force of the Sun could fling a comet out of the Solar System altogether.
Human beings have wanted to know more about comets since the Chinese recorded Comet Halley in 240 BC. Several robot explorers have been sent out toward comets to take a closer look. Here is a compilation of all of the deep space missions from Earth that have made contributions to the study of comets, even though some of the missions, such as Galileo and Ulysses, have not had comets as their primary targets.
Current and Proposed Comet-Related MissionsPast Comet Missions
Stardust
NASA concept of Stardust capsule
after landing in Utah.
Click image to learn more.
Comet Sample Return Mission
Launch - February 7, 1999
Comet Wild 2 - 2004
Sample Return - 2006
LEARN MORE ABOUT STARDUST
Galileo
Jupiter Orbiter/Probe Mission
Comet Shoemaker-Levy 9 - 1994
Interplanetary Dust Storm - 1995
LEARN MORE
Ulysses
Sun Polar Orbiter Mission
Dust Detection Near Jupiter - 1992
First Detection of Interstellar Dust
Ulysses Comet Watch Program
LEARN MORE
Rosetta
European Comet Lander/Orbiter Mission
Launch - January 2003
Comet Wirtanen - 2011
LEARN MORE
Deep Impact
Impact the comet nucleus
Launch - 2004
Comet 9P/Tempel 1 - 2005
LEARN MOREISEE-3/ICE
Lost Comet Missions
First Ever Comet Encounter
Comet Giacobini-Zinner - 1985
Comet Halley - 1986
LEARN MORE
Giotto
ESA's First Deep Space Mission
Comet Halley - 1986
Comet Grigg-Skjellerup - 1992
LEARN MORE
Vega 1 & 2
USSR Venus & Comet Mission
Comet Halley - 1986
LEARN MORE
Sakigake & Suisei
Japan's First Deep Space Missions
Comet Halley - 1986
LEARN MORE
Deep Space 1 (DS1)
Asteroid/Comet Flyby Mission
Launch - October 1998
Asteroid Braille - 1999
Comet Borrelly - 2001
Retired Dec. 18, 2001
LEARN MOREComet Nucleus Tour (CONTOUR)
Comet Flyby Mision
Launch - July 2002
was to have visited:
Comet Encke - 2003
Comet Schwassmann-Wachmann-3 - 2006
Comet d'Arrest - 2008
LEARN MORE
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