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= = Atmosphere = =
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There are indications that Ceres may have a tenuous water vapor atmosphere outgassing from water ice on the surface .
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Surface water ice is unstable at distances less than 5 AU from the Sun , so it is expected to sublime if it is exposed directly to solar radiation . Water ice can migrate from the deep layers of Ceres to the surface , but escapes in a very short time . As a result , it is difficult to detect water vaporization . Water escaping from polar regions of Ceres was possibly observed in the early 1990s but this has not been unambiguously demonstrated . It may be possible to detect escaping water from the surroundings of a fresh impact crater or from cracks in the subsurface layers of Ceres . Ultraviolet observations by the IUE spacecraft detected statistically significant amounts of hydroxide ions near Ceres ' north pole , which is a product of water vapor dissociation by ultraviolet solar radiation .
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In early 2014 , using data from the Herschel Space Observatory , it was discovered that there are several localized ( not more than 60 km in diameter ) mid @-@ latitude sources of water vapor on Ceres , which each give off approximately 1026 molecules ( or 3 kg ) of water per second . Two potential source regions , designated Piazzi ( 123 ° E , 21 ° N ) and Region A ( 231 ° E , 23 ° N ) , have been visualized in the near infrared as dark areas ( Region A also has a bright center ) by the W. M. Keck Observatory . Possible mechanisms for the vapor release are sublimation from approximately 0 @.@ 6 km2 of exposed surface ice , or cryovolcanic eruptions resulting from radiogenic internal heat or from pressurization of a subsurface ocean due to growth of an overlying layer of ice . Surface sublimation would be expected to be lower when Ceres is farther from the Sun in its orbit , whereas internally powered emissions should not be affected by its orbital position . The limited data available are more consistent with cometary @-@ style sublimation .
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= = Origin and evolution = =
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Ceres is possibly a surviving protoplanet ( planetary embryo ) , which formed 4 @.@ 57 billion years ago in the asteroid belt . Although the majority of inner Solar System protoplanets ( including all lunar- to Mars @-@ sized bodies ) either merged with other protoplanets to form terrestrial planets or were ejected from the Solar System by Jupiter , Ceres is thought to have survived relatively intact . An alternative theory proposes that Ceres formed in the Kuiper belt and later migrated to the asteroid belt . The discovery of ammonia salts in Occator crater supports an origin in the outer Solar System . Another possible protoplanet , Vesta , is less than half the size of Ceres ; it suffered a major impact after solidifying , losing ~ 1 % of its mass .
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The geological evolution of Ceres was dependent on the heat sources available during and after its formation : friction from planetesimal accretion , and decay of various radionuclides ( possibly including short @-@ lived isotopes such as the cosmogenic nuclide aluminium @-@ 26 ) . These are thought to have been sufficient to allow Ceres to differentiate into a rocky core and icy mantle soon after its formation . This process may have caused resurfacing by water volcanism and tectonics , erasing older geological features . Due to its small size , Ceres would have cooled early in its existence , causing all geological resurfacing processes to cease . Any ice on the surface would have gradually sublimated , leaving behind various hydrated minerals like clay minerals and carbonates .
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Today , Ceres appears to be a geologically inactive body , with a surface sculpted only by impacts . The presence of significant amounts of water ice in its composition raises the possibility that Ceres has or had a layer of liquid water in its interior . This hypothetical layer is often called an ocean . If such a layer of liquid water exists , it is hypothesized to be located between the rocky core and ice mantle like that of the theorized ocean on Europa . The existence of an ocean is more likely if solutes ( i.e. salts ) , ammonia , sulfuric acid or other antifreeze compounds are dissolved in the water .
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= = Potential habitability = =
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Although not as actively discussed as a potential home for microbial extraterrestrial life as Mars , Titan , Europa or Enceladus , there is evidence that Ceres ' icy mantle was once a watery subterranean ocean , and that has led to speculations that life could have existed there , and that hypothesized ejecta bearing microorganisms could have come from Ceres to Earth .
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= = Observation and exploration = =
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= = = Observation = = =
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When Ceres has an opposition near the perihelion , it can reach a visual magnitude of + 6 @.@ 7 . This is generally regarded as too dim to be seen with the naked eye , but under exceptional viewing conditions a very sharp @-@ sighted person may be able to see it . Ceres was at its brightest ( 6 @.@ 73 ) on 18 December 2012 . The only other asteroids that can reach a similarly bright magnitude are 4 Vesta , and , during rare oppositions near perihelion , 2 Pallas and 7 Iris . At a conjunction Ceres has a magnitude of around + 9 @.@ 3 , which corresponds to the faintest objects visible with 10 × 50 binoculars . It can thus be seen with binoculars whenever it is above the horizon of a fully dark sky .
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Some notable observations and milestones for Ceres include :
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1984 November 13 : An occultation of a star by Ceres observed in Mexico , Florida and across the Caribbean .
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1995 June 25 : Ultraviolet Hubble Space Telescope images with 50 @-@ kilometer resolution .
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2002 : Infrared images with 30 km resolution taken with the Keck telescope using adaptive optics .
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2003 and 2004 : Visible light images with 30 km resolution ( the best prior to the Dawn mission ) taken using Hubble .
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2012 December 22 : Ceres occulted the star TYC 1865 @-@ 00446 @-@ 1 over parts of Japan , Russia , and China . Ceres ' brightness was magnitude 6 @.@ 9 and the star , 12 @.@ 2 .
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2014 : Ceres was found to have an atmosphere with water vapor , confirmed by the Herschel space telescope .
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2015 : The NASA Dawn spacecraft approached and orbited Ceres , sending detailed images and scientific data back to Earth .
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= = = Exploration = = =
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In 1981 , a proposal for an asteroid mission was submitted to the European Space Agency ( ESA ) . Named the Asteroidal Gravity Optical and Radar Analysis ( AGORA ) , this spacecraft was to launch some time in 1990 – 1994 and perform two flybys of large asteroids . The preferred target for this mission was Vesta . AGORA would reach the asteroid belt either by a gravitational slingshot trajectory past Mars or by means of a small ion engine . However , the proposal was refused by ESA . A joint NASA – ESA asteroid mission was then drawn up for a Multiple Asteroid Orbiter with Solar Electric Propulsion ( MAOSEP ) , with one of the mission profiles including an orbit of Vesta . NASA indicated they were not interested in an asteroid mission . Instead , ESA set up a technological study of a spacecraft with an ion drive . Other missions to the asteroid belt were proposed in the 1980s by France , Germany , Italy , and the United States , but none were approved . Exploration of Ceres by fly @-@ by and impacting penetrator was the second main target of the second plan of the multiaimed Soviet Vesta mission , developed in cooperation with European countries for realisation in 1991 – 1994 but canceled due to the Soviet Union disbanding .
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In the early 1990s , NASA initiated the Discovery Program , which was intended to be a series of low @-@ cost scientific missions . In 1996 , the program 's study team recommended as a high priority a mission to explore the asteroid belt using a spacecraft with an ion engine . Funding for this program remained problematic for several years , but by 2004 the Dawn vehicle had passed its critical design review .
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It was launched on 27 September 2007 , as the space mission to make the first visits to both Vesta and Ceres . On 3 May 2011 , Dawn acquired its first targeting image 1 @.@ 2 million kilometers from Vesta . After orbiting Vesta for 13 months , Dawn used its ion engine to depart for Ceres , with gravitational capture occurring on 6 March 2015 at a separation of 61 @,@ 000 km , four months prior to the New Horizons flyby of Pluto .
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Dawn 's mission profile calls for it to study Ceres from a series of circular polar orbits at successively lower altitudes . It entered its first observational orbit ( " RC3 " ) around Ceres at an altitude of 13 @,@ 500 km on 23 April 2015 , staying for only approximately one orbit ( fifteen days ) . The spacecraft will subsequently reduce its orbital distance to 4 @,@ 400 km for its second observational orbit ( " survey " ) for three weeks , then down to 1 @,@ 470 km ( " HAMO " ) for two months and then down to its final orbit at 375 km ( " LAMO " ) for at least three months . The spacecraft instrumentation includes a framing camera , a visual and infrared spectrometer , and a gamma @-@ ray and neutron detector . These instruments will examine Ceres ' shape and elemental composition . On 13 January 2015 , Dawn took the first images of Ceres at near @-@ Hubble resolution , revealing impact craters and a small high @-@ albedo spot on the surface , near the same location as that observed previously . Additional imaging sessions , at increasingly better resolution took place on 25 January , 4 , 12 , 19 , and 25 February , 1 March , and 10 and 15 April .
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Dawn 's arrival in a stable orbit around Ceres was delayed after , close to reaching Ceres , it was hit by a cosmic ray , making it take another , longer route around Ceres in back , instead of a direct spiral towards it .
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The Chinese Space Agency is designing a sample retrieval mission from Ceres that would take place during the 2020s .
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= = Maps = =
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= = = Map of quadrangles = = =
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The following imagemap of the dwarf planet Ceres is divided into 15 quadrangles . They are named after the first craters whose names the IAU approved in July 2015 . The map image ( s ) were taken by the Dawn space probe .
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= = Gallery = =
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= = = True @-@ color images = = =
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= = = Animations = = =
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= Skye =
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Skye , or the Isle of Skye ( / skaɪ / ; Scottish Gaelic : An t @-@ Eilean Sgitheanach or Eilean a ' Cheò ) , is the largest and most northerly major island in the Inner Hebrides of Scotland . The island 's peninsulas radiate from a mountainous centre dominated by the Cuillins , the rocky slopes of which provide some of the most dramatic mountain scenery in the country . Although it has been suggested that the Gaelic Sgitheanach describes a winged shape there is no definitive agreement as to the name 's origins .
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The island has been occupied since the Mesolithic period and its history includes a time of Norse rule and a long period of domination by Clan MacLeod and Clan Donald . The 18th @-@ century Jacobite risings led to the breaking up of the clan system and subsequent Clearances that replaced entire communities with sheep farms , some of which also involved forced emigrations to distant lands . Resident numbers declined from over 20 @,@ 000 in the early 19th century to just under 9 @,@ 000 by the closing decade of the 20th century . Skye 's population increased by 4 per cent between 1991 and 2001 . About a third of the residents were Gaelic speakers in 2001 , and although their numbers are in decline this aspect of island culture remains important .
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The main industries are tourism , agriculture , fishing and forestry . Skye is part of the Highland Council local government area . The island 's largest settlement is Portree , known for its picturesque harbour . There are links to various nearby islands by ferry and , since 1995 , to the mainland by a road bridge . The climate is mild , wet and windy . The abundant wildlife includes the golden eagle , red deer and Atlantic salmon . The local flora is dominated by heather moor , and there are nationally important invertebrate populations on the surrounding sea bed . Skye has provided the locations for various novels and feature films and is celebrated in poetry and song .
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= = Etymology = =
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The first written references to the island are Roman sources such as the Ravenna Cosmography , which refers to Scitis and Scetis , which can be found on a map by Ptolemy . One possible derivation comes from skitis , an early Celtic word for winged , which may describe how the island 's peninsulas radiate out from a mountainous centre . Subsequent Gaelic- , Norse- and English @-@ speaking peoples have influenced the history of Skye ; the relationships between their names for the island are not straightforward . Various etymologies have been proposed , such as the " winged isle " or " the notched isle " but no definitive solution has been found to date and the placename may be from an earlier , non @-@ Gaelic language .
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In the Norse sagas Skye is called Skíð , for example in the Hákonar saga Hákonarsonar and a skaldic poem in the Heimskringla from c . 1230 contains a line that translates as " the hunger battle @-@ birds were filled in Skye with blood of foemen killed " . The island was also referred to by the Norse as Skuy ( misty isle ) , Skýey or Skuyö ( isle of cloud ) . The traditional Gaelic name is An t @-@ Eilean Sgitheanach ( the island of Skye ) , An t @-@ Eilean Sgiathanach being a more recent and less common spelling . In 1549 Donald Munro , High Dean of the Isles , wrote of " Sky " : " This Ile is callit Ellan Skiannach in Irish , that is to say in Inglish the wyngit Ile , be reason it has mony wyngis and pointis lyand furth fra it , throw the dividing of thir foirsaid Lochis . " but the meaning of this Gaelic name is unclear .
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Eilean a ' Cheò , which means island of the mist ( a translation of the Norse name ) , is a poetic Gaelic name for the island .
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= = Geography = =
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At 1 @,@ 656 square kilometres ( 639 sq mi ) , Skye is the second @-@ largest island in Scotland after Lewis and Harris . The coastline of Skye is a series of peninsulas and bays radiating out from a centre dominated by the Cuillin hills ( Gaelic : An Cuiltheann ) . Malcolm Slesser suggested that its shape " sticks out of the west coast of northern Scotland like a lobster 's claw ready to snap at the fish bone of Harris and Lewis " and W. H. Murray , commenting on its irregular coastline , stated that " Skye is sixty miles [ 100 km ] long , but what might be its breadth is beyond the ingenuity of man to state " . Martin Martin , a native of the island , reported on it at length in a 1703 publication . His geological observations included a note that :
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There are marcasites black and white , resembling silver ore , near the village Sartle : there are likewise in the same place several stones , which in bigness , shape , & c . , resemble nutmegs , and many rivulets here afford variegated stones of all colours . The Applesglen near Loch @-@ Fallart has agate growing in it of different sizes and colours ; some are green on the outside , some are of a pale sky colour , and they all strike fire as well as flint : I have one of them by me , which for shape and bigness is proper for a sword handle . Stones of a purple colour flow down the rivulets here after great rains .
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The Black Cuillin , which are mainly composed of basalt and gabbro , include twelve Munros and provide some of the most dramatic and challenging mountain terrain in Scotland . The ascent of Sgùrr a ' Ghreadaidh is one of the longest rock climbs in Britain and the Inaccessible Pinnacle is the only peak in Scotland that requires technical climbing skills to reach the summit . These hills make demands of the hill walker that exceed any others found in Scotland and a full traverse of the Cuillin ridge may take 15 – 20 hours . The Red Hills ( Gaelic : Am Binnean Dearg ) to the south are also known as the Red Cuillin . They are mainly composed of granite that has weathered into more rounded hills with many long scree slopes on their flanks . The highest point of these hills is Glamaig , one of only two Corbetts on Skye .
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The northern peninsula of Trotternish is underlain by basalt , which provides relatively rich soils and a variety of unusual rock features . The Kilt Rock is named after the tartan @-@ like patterns in the 105 metres ( 344 ft ) cliffs . The Quiraing is a spectacular series of rock pinnacles on the eastern side of the main spine of the peninsula and further south is the rock pillar of the Old Man of Storr .
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Beyond Loch Snizort to the west of Trotternish is the Waternish peninsula , which ends in Ardmore Point 's double rock arch . Duirinish is separated from Waternish by Loch Dunvegan , which contains the island of Isay . The loch is ringed by sea cliffs that reach 295 metres ( 967 ft ) at Waterstein Head . Oolitic loam provides good arable land in the main valley . Lochs Bracadale and Harport and the island of Wiay lie between Duirinish and Minginish , which includes the narrower defiles of Talisker and Glen Brittle and whose beaches are formed from black basaltic sands . Strathaird is a relatively small peninsula close to the Cuillin hills with only a few crofting communities , the island of Soay lies offshore . The bedrock of Sleat in the south is Torridonian sandstone , which produces poor soils and boggy ground , although its lower elevations and relatively sheltered eastern shores enable a lush growth of hedgerows and crops . The islands of Raasay , Rona , Scalpay and Pabay all lie to the north and east between Skye and the mainland .
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= = = Towns and villages = = =
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Portree in the north at the base of Trotternish is the largest settlement ( estimated population 2 @,@ 264 in 2011 ) and is the main service centre on the island . Broadford , the location of the island 's only airstrip , is on the east side of the island and Dunvegan in the north @-@ west is well known for its castle and the nearby Three Chimneys restaurant . The 18th @-@ century Stein Inn on the Waternish coast is the oldest pub on Skye . Kyleakin is linked to Kyle of Lochalsh on the mainland by the Skye Bridge , which spans the narrows of Loch Alsh . Uig , the port for ferries to the Outer Hebrides , is on the west of the Trotternish peninsula and Edinbane is between Dunvegan and Portree . Much of the rest of the population lives in crofting townships scattered around the coastline .
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= = = Climate = = =
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The influence of the Atlantic Ocean and the Gulf Stream create a mild oceanic climate . Temperatures are generally cool , averaging 6 @.@ 5 ° C ( 43 @.@ 7 ° F ) in January and 15 @.@ 4 ° C ( 59 @.@ 7 ° F ) in July at Duntulm in Trotternish . Snow seldom lies at sea level and frosts are less frequent than on the mainland . Winds are a limiting factor for vegetation . South @-@ westerlies are the most common and speeds of 128 km / h ( 80 mph ) have been recorded . High winds are especially likely on the exposed coasts of Trotternish and Waternish . In common with most islands of the west coast of Scotland , rainfall is generally high at 1 @,@ 500 – 2 @,@ 000 mm ( 59 – 79 in ) per annum and the elevated Cuillin are wetter still . Variations can be considerable , with the north tending to be drier than the south . Broadford , for example , averages more than 2 @,@ 870 mm ( 113 in ) of rain per annum . Trotternish typically has 200 hours of bright sunshine in May , the sunniest month . On 28 December 2015 , the temperature reached 15 ° C , beating the previous December record of 12 @.@ 9 ° C , set in 2013 . On 9 May 2016 , a temperature of 26 @.@ 7 ° C ( 80 @.@ 1 ° F ) was recorded at Lusa in the south @-@ east of the island .
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= = History = =
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= = = Prehistory = = =
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A Mesolithic hunter @-@ gatherer site dating to the 7th millennium BC at An Corran in Staffin is one of the oldest archaeological sites in Scotland . Its occupation is probably linked to that of the rock shelter at Sand , Applecross , on the mainland coast of Wester Ross where tools made of a mudstone from An Corran have been found . Surveys of the area between the two shores of the Inner Sound and Sound of Raasay have revealed 33 sites with potentially Mesolithic deposits . Finds of bloodstone microliths on the foreshore at Orbost on the west coast of the island near Dunvegan also suggest Mesolithic occupation . These tools probably originate from the nearby island of Rum .
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Rubha an Dùnain , an uninhabited peninsula to the south of the Cuillin , has a variety of archaeological sites dating from the Neolithic onwards . There is a 2nd or 3rd millennium BC chambered cairn , an Iron Age promontory fort and the remains of other prehistoric settlement dating from the Bronze Age nearby . Loch na h @-@ Airde on the peninsula is linked to the sea by an artificial " Viking " canal that may date from the later period of Norse settlement . Dun Ringill is a ruined Iron Age hill fort on the Strathaird peninsula , which was further fortified in the Middle Ages and may have become the seat of Clan MacKinnon .
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= = = Early history = = =
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The late Iron Age inhabitants of the northern and western Hebrides were probably Pictish , although the historical record is sparse . Three Pictish symbol stones have been found on Skye and a fourth on Raasay . More is known of the kingdom of Dál Riata to the south ; Adomnán 's life of Columba , written shortly before 697 , portrays the saint visiting Skye ( where he baptised a pagan leader using an interpreter ) and Adomnán himself is thought to have been familiar with the island . The Irish annals record a number of events on Skye in the later 7th and early 8th centuries – mainly concerning the struggles between rival dynasties that formed the background to the Old Irish language romance Scéla Cano meic Gartnáin .
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The Norse held sway throughout the Hebrides from the 9th century until after the Treaty of Perth in 1266 . However , apart from placenames , little remains of their presence on Skye in the written or archaeological record . Apart from the name " Skye " itself , all pre @-@ Norse placenames seem to have been obliterated by the Scandinavian settlers . Viking heritage is claimed by Clan MacLeod and Norse tradition is celebrated in the winter fire festival at Dunvegan , during which a replica Viking long boat is set alight .
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= = = Clans and Scottish rule = = =
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