Editing Comet (section)

=== Spacecraft missions ===
{{See also|List of comets visited by spacecraft|List of missions to comets}}
*The [[Halley Armada]] describes the collection of spacecraft missions that visited and/or made observations of Halley's Comet 1980s perihelion. The space shuttle ''Challenger'' was intended to do a study of Halley's Comet in 1986, but exploded shortly after being launched.
*'''Deep Impact'''. Debate continues about how much ice is in a comet. In 2001, the ''[[Deep Space 1]]'' spacecraft obtained high-resolution images of the surface of [[19P/Borrelly|Comet Borrelly]]. It was found that the surface of comet Borrelly is hot and dry, with a temperature of between {{convert|26|and|71|C|F}}, and extremely dark, suggesting that the ice has been removed by solar heating and maturation, or is hidden by the soot-like material that covers Borrelly.<ref>{{cite web |title=NASA Spacecraft Finds Comet Has Hot, Dry Surface |url=http://www.jpl.nasa.gov/releases/2002/release_2002_80.html |publisher=JPL |date=5 April 2002 |access-date=22 August 2013 |archive-date=12 October 2012 |archive-url=https://web.archive.org/web/20121012140123/http://www.jpl.nasa.gov/releases/2002/release_2002_80.html |url-status=dead }}</ref> In July 2005, the ''[[Deep Impact (spacecraft)|Deep Impact]]'' probe blasted a crater on Comet [[Tempel 1]] to study its interior. The mission yielded results suggesting that the majority of a comet's water ice is below the surface and that these reservoirs feed the jets of vaporized water that form the coma of Tempel 1.<ref>{{cite web |title=NASA's 'Deep Impact' Team Reports First Evidence of Cometary Ice |url=http://www.brown.edu/Administration/News_Bureau/2005-06/05-072.html |publisher=Brown University |date=2 February 2006 |access-date=22 August 2013}}</ref> Renamed [[EPOXI]], it made a flyby of [[103P/Hartley|Comet Hartley 2]] on 4 November 2010.
*'''Ulysses'''. In 2007, the [[Ulysses (spacecraft)|Ulysses probe]] unexpectedly passed through the tail of the comet [[C/2006 P1 (McNaught)|C/2006 P1]] (McNaught) which was discovered in 2006. Ulysses was launched in 1990 and the intended mission was for Ulysses to orbit around the Sun for further study at all latitudes. 
*'''Stardust'''. Data from the [[Stardust (spacecraft)|''Stardust'' mission]] show that materials retrieved from the tail of Wild 2 were crystalline and could only have been "born in fire", at extremely high temperatures of over {{convert|1000|C|F}}.<ref>{{cite news |last=Rincon |first=Paul |title=Comets 'are born of fire and ice' |url=http://news.bbc.co.uk/2/hi/science/nature/4801968.stm |work=BBC News |date=14 March 2006 |access-date=7 September 2013}}</ref><ref>{{cite web |last=Malik |first=T. |title=NASA's Stardust Comet Samples Contain Minerals Born in Fire |url=http://www.space.com/scienceastronomy/060313_stardust_update.html |publisher=Space.com |date=13 March 2006 |access-date=7 September 2013}}</ref> Although comets formed in the outer Solar System, radial mixing of material during the early formation of the Solar System is thought to have redistributed material throughout the proto-planetary disk.<ref>{{cite journal |doi=10.1038/nature03088 |title=The building blocks of planets within the 'terrestrial' region of protoplanetary disks |date=2004 |last1=Van Boekel |first1=R. |last2=Min |first2=M. |last3=Leinert |first3=Ch. |last4=Waters |first4=L.B.F.M. |last5=Richichi |first5=A. |last6=Chesneau |first6=O. |last7=Dominik |first7=C. |last8=Jaffe |first8=W. |last9=Dutrey |first9=A. |last10=Graser |first10=U. |last11=Henning |first11=Th. |last12=De Jong |first12=J. |last13=Köhler |first13=R. |last14=De Koter |first14=A. |last15=Lopez |first15=B. |last16=Malbet |first16=F. |last17=Morel |first17=S. |last18=Paresce |first18=F. |last19=Perrin |first19=G. |last20=Preibisch |first20=Th. |last21=Przygodda |first21=F. |last22=Schöller |first22=M. |last23=Wittkowski |first23=M. |display-authors=1 |journal=Nature |volume=432 |issue=7016 |pages=479–82 |pmid=15565147 |bibcode=2004Natur.432..479V|s2cid=4362887 }}</ref> As a result, comets contain crystalline grains that formed in the early, hot inner Solar System. This is seen in comet spectra as well as in sample return missions. More recent still, the materials retrieved demonstrate that the "comet dust resembles asteroid materials".<ref>{{cite web |title=Stardust comet dust resembles asteroid materials |url=https://publicaffairs.llnl.gov/news/news_releases/2008/NR-08-01-05.html |publisher=Lawrence Livermore National Laboratory |date=24 January 2008 |access-date=7 September 2013 |url-status=dead |archive-url=https://web.archive.org/web/20100528001619/https://publicaffairs.llnl.gov/news/news_releases/2008/NR-08-01-05.html |archive-date=28 May 2010 }}</ref> These new results have forced scientists to rethink the nature of comets and their distinction from asteroids.<ref>{{cite news |last=Dunham |first=Will |title=Dust samples prompt rethink about comets |url=https://www.reuters.com/article/us-comet-idUSN2537011620080126 |work=Reuters |date=25 January 2008 |access-date=7 September 2013}}</ref>
*'''Rosetta'''. The ''[[Rosetta (spacecraft)|Rosetta]]'' probe orbited [[67P/Churyumov–Gerasimenko|Comet Churyumov–Gerasimenko]]. On 12 November 2014, its lander ''Philae'' successfully landed on the comet's surface, the first time a spacecraft has ever landed on such an object in history.<ref>{{cite web |url=http://sci.esa.int/rosetta/34479-rosetta-ready-to-explore-a-comet-s-realm/ |title=Rosetta Ready To Explore A Comet's Realm |publisher=European Space Agency |date=12 January 2004 |access-date=7 September 2013}}</ref>