Mercury (planet) and Night Electric Night: Difference between pages

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m *at least in the lead*, I think adding Fahrenheit doesn't harm: see WP:MTAA. Also, values are likely not intended to be precise to three significant digits, and using minus instead of hyphen.
 
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{{future album}}
{{This|the planet|Mercury}}
{{Infobox Album | <!-- See Wikipedia:WikiProject_Albums -->
{{pp-semi-vandalism|small=yes}}
| Name = Night Electric Night
{{featured article}}
| Type = studio
<!--
| Artist = [[Deathstars]]
Please note the formatting and layout of this infobox has been matched with the other bodies of the Solar System. Please do not arbitrarily change it without discussion.
| Cover = Nocover.png
Scroll down to edit the contents of this page.
| Released = [[January]] [[2009]]
Additional parameters for this template are available at [[Template:Infobox Planet]].
| Recorded = November 2007–present in [[New York City]] and [[Sweden]]
-->
| Genre =
{{Infobox Planet
| bgcolour = #D8BBA6
| Length =
| Label = [[Nuclear Blast]]
| name = Mercury
| Producer = [[Emil Nödtveidt|Nightmare Industries]]
| symbol = [[Image:mercury symbol.svg|25px|Astronomical symbol of mercury]]
| Last album = ''[[Termination Bliss]]''<br />(2006)
| image = [[Image:Mercury in color - Prockter07 centered.jpg|240px|Mercury]]
| This album = '''''Night Electric Night'''''<br />(2009)
| caption = [[MESSENGER]] false color image of Mercury
| Next album =
| orbit_ref =<ref name=horizons>{{cite web
| date=[[April 7]], [[2008]] | first=Donald K. | last=Yeomans
| url=http://ssd.jpl.nasa.gov/?horizons
| title=HORIZONS System
| publisher=NASA JPL | accessdate=2008-04-07 }}</ref>
| epoch = [[J2000]]
| aphelion = 69&nbsp;816&nbsp;900 km<br />0.466&nbsp;697 [[Astronomical unit|AU]]
| perihelion = 46&nbsp;001&nbsp;200 km<br />0.307&nbsp;499 AU
| semimajor = 57&nbsp;909&nbsp;100 km<br />0.387&nbsp;098 AU
| eccentricity = 0.205&nbsp;630<ref name="nssdcMercury" />
| period = 87.969&nbsp;1 [[day|d]]<br/>(0.240&nbsp;846 [[julian year (astronomy)|a]])
| synodic_period = 115.88&nbsp;d<ref name="nssdcMercury">{{cite web|title=Mercury Fact Sheet|url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html|publisher=[[NASA]] Goddard Space Flight Center | date=[[November 30]], [[2007]] |accessdate=2008-05-28}}</ref>
| avg_speed = 47.87 km/s<ref name="nssdcMercury" />
| inclination = 7.005°<br />3.38° to Sun’s equator
| asc_node = 48.331°
| arg_peri = 29.124°
| mean_anomaly = 174.796°
| satellites = None
| physical_characteristics = yes
diameter = 4880 km
| mean_radius = 2439.7&nbsp;±&nbsp;1.0&nbsp;km<ref name=nasa>{{cite web
| date=[[February 25]], [[2008]] | first=Kirk | last=Munsell
| coauthors=Smith, Harman; Harvey, Samantha
| url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mercury&Display=Facts
| title=Mercury: Facts & Figures
| work=Solar System Exploration
| publisher=NASA | accessdate=2008-04-07 }}
</ref><ref name=Seidelmann2007>{{cite journal
| last= Seidelmann| first= P. Kenneth
| coauthors= Archinal, B. A.; A’hearn, M. F.; et.al.
| title= Report of the IAU/IAGWorking Group on cartographic coordinates and rotational elements: 2006
| journal= Celestial Mechanics and Dynamical Astronomy
| volume=90 | pages=155–180 | year=2007
| doi=10.1007/s10569-007-9072-y
| url=http://adsabs.harvard.edu/doi/10.1007/s10569-007-9072-y
| accessdate=2007-08-28 }}</ref><br />0.3829 Earths
| flattening = < 0.0006<ref name=Seidelmann2007/> <!-- calculated from data in ref name=Seidelmann2007 -->
| surface_area = 7.48{{e|7}}&nbsp;km²<br />0.108 Earths<ref name=nasa/>
| volume = 6.083{{e|10}}&nbsp;km³<br />0.054 Earths<ref name=nasa/>
| mass = 3.3022{{e|23}}&nbsp;kg<br />0.055 Earths<ref name=nasa/>
| density = 5.427&nbsp;g/cm³<ref name=nasa/>
| surface_grav = 3.7&nbsp;[[Acceleration|m/s²]]<br />0.38 [[g-force|g]]<ref name=nasa/>
| escape_velocity = 4.25&nbsp;km/s<ref name=nasa/>
| sidereal_day = 58.646 day<br>1407.5&nbsp;[[hour|h]]<ref name=nasa/>
| rot_velocity = 10.892 km/h
| axial_tilt = 2.11′&nbsp;±&nbsp;0.1′<ref name=Margot2007>{{cite journal| last=Margot | first=L.J.| coauthors=Peale, S. J.; Jurgens, R. F.; Slade, M. A.; Holin, I. V.| title=Large Longitude Libration of Mercury Reveals a Molten Core| journal=Science| year=2007 | volume=316 | pages=710&ndash;714| doi=10.1126/science.1140514
| url=http://adsabs.harvard.edu/abs/2007Sci...316..710M| pmid=17478713}}</ref>
| right_asc_north_pole = 18 h 44 min 2 s<br/>281.01°<ref name="nssdcMercury" />
| declination = 61.45°<ref name="nssdcMercury" />
| albedo = 0.119 ([[Bond albedo|bond]])<br/>
0.106 ([[Geometric albedo|geom.]])<ref name="nssdcMercury" />
| magnitude = up to &minus;1.9<ref name="nssdcMercury" />
| angular_size = 4.5" &ndash; 13"<ref name="nssdcMercury" />
| temperatures = yes
| temp_name1 = 0°N, 0°W <!-- Vasavada et al. 1999-->
| min_temp_1 = 100 K
| mean_temp_1 = 340 K
| max_temp_1 = 700 K
| temp_name2 = 85°N, 0°W
| min_temp_2 = 80 K
| mean_temp_2 = 200 K
| max_temp_2 = 380 K
| adjectives = Mercurian, Mercurial<ref>{{cite web
| url=http://www.merriam-webster.com/dictionary/mercurial
| publisher=Merriam-Webster Online
| title=mercurial | accessdate=2008-06-12 }}</ref>
| atmosphere = yes
| surface_pressure = trace
| atmosphere_composition = 42% Molecular [[oxygen]]<br />29.0% [[sodium]]<br />22.0% [[hydrogen]]<br />6.0% [[helium]]<br />0.5% [[potassium]]<br />Trace amounts of [[argon]], [[nitrogen]], [[carbon dioxide]], [[Water|water vapor]], [[xenon]], [[krypton]], & [[neon]]<ref name="nssdcMercury" />
}}
}}
'''Mercury''' (pronounced {{Audio-IPA|en-us-Mercury.ogg|/ˈmɝːkjʊəri/}}) is the innermost and smallest [[planet]] in the [[solar system]],<ref>[[Pluto]] was once considered the smallest, but is now classified as a [[dwarf planet]].</ref> [[orbit]]ing the [[Sun]] once every 88 days. Mercury is bright when viewed from [[Earth]], ranging from −2.0 to 5.5 in [[apparent magnitude]], but is not easily seen as its greatest [[Elongation (astronomy)|angular separation from the Sun]] is only 28.3°. It can only be seen in morning or evening [[twilight]]. Comparatively little is known about it; the first of two [[spacecraft]] to visit Mercury was [[Mariner 10|Mariner&nbsp;10]], which mapped only about 45% of the planet’s surface from 1974 to 1975. The second is the [[MESSENGER|MESSENGER spacecraft]], which mapped another 30% during its flyby of January 14, 2008. MESSENGER will make two more passes by Mercury, followed by orbital insertion in 2011, and will then survey and map the entire planet.


'''''Night Electric Night''''' is the third [[studio album]] by [[Sweden|Swedish]] [[industrial metal]] band [[Deathstars]]. It is scheduled for release in [[January]] [[2009]] by [[Nuclear Blast]]. The album was initially recorded under the working title ''Deathglam''.
Mercury is similar in appearance to the [[Moon]]: It is heavily [[impact crater|cratered]], has no [[natural satellite]]s and no substantial [[Celestial body atmosphere|atmosphere]]. However, unlike the moon, it has a large [[iron]] [[planetary core|core]], which generates a [[magnetic field]] about 1% as strong as that of the [[Earth]].<ref>{{cite web |url=http://www-spc.igpp.ucla.edu/personnel/russell/papers/merc_mag/|title=Mercury magnetic field|publisher=C. T. Russell & J. G. Luhmann|accessdate=2007-03-16}}</ref> It is an exceptionally dense planet due to the large relative size of its core. Surface temperatures range from about 90 to {{nowrap|700 [[Kelvin|K]]}} (−180&nbsp;°C to 430&nbsp;°C, −220&nbsp;°F to 800&nbsp;°F),<ref name="ESAs&t">{{cite web|url=http://sci.esa.int/science-e/www/category/index.cfm?fcategoryid=4586|title=Background Science|publisher=European Space Agency|accessdate=2008-05-23}}</ref> with the [[subsolar point]] being the hottest and the bottoms of craters near the [[Geographical pole|poles]] being the coldest.


==Album title==
[[#Ancient astronomers|Recorded observations]] of Mercury date back to at least the first millennium BC. Before the 4th century BC, Greek astronomers believed the planet to be two separate objects: one visible only at sunrise, which they called [[Apollo]]; the other visible only at sunset, which they called [[Hermes]].<ref name="Dunne">{{cite book|title=The Voyage of Mariner&nbsp;10 — Mission to Venus and Mercury|author=Dunne, J. A. and Burgess, E.|chapterurl=http://history.nasa.gov/SP-424/ch1.htm|publisher=NASA History Office|year=1978|chapter=Chapter One|url=http://history.nasa.gov/SP-424/}}</ref> The English name for the planet comes from the [[Ancient Rome|Romans]], who named it after the Roman [[Roman mythology|god]] [[Mercury (mythology)|Mercury]], which they equated with the Greek [[Hermes]]. The [[astronomical symbol]] for Mercury is a stylized version of Hermes' [[caduceus]].<ref>{{cite book|title=Astronomy: A Textbook|first=John Charles|last=Duncan|year=1946|publisher=Harper & Brothers|pages=125|quote=The symbol for Mercury represents the Caduceus, a wand with two serpents twined
Production of the third album by Deathstars was revealed in an interview with the band conducted by Anthony Morgan of Lucem Fero in early [[2008]], where it was referred to by its working title, ''Deathglam''.<ref>[http://www.lucemfero.com/deathstars012008.php]</ref> Vocalist [[Andreas Bergh|Whiplasher Bernadotte]] expanded on the title, saying, ". . . it'll just continue with the deathglam that we play. In terms of this new album's style, I think it's more Deathstars than ever . . ."
around it, which was carried by the messenger of the gods.}}</ref>


Recently, the band has announced on their official website that the record has been re-dubbed ''Night Electric Night''.
==Internal structure==
Mercury is one of four [[terrestrial planet]]s in the [[solar system]], and is a rocky body like the Earth. It is the smallest planet in the solar system, with an [[equator]]ial [[radius]] of 2439.7&nbsp;km.<ref name="nssdcMercury" /> Mercury is even [[list of solar system objects by radius|smaller]]&mdash;albeit more massive&mdash;than the [[List of moons by diameter|largest]] [[natural satellite]]s in the solar system, [[Ganymede (moon)|Ganymede]] and [[Titan (moon)|Titan]]. Mercury consists of approximately 70% [[metal]]lic and 30% [[silicate]] material.<ref name="strom" /> Mercury's density is the second highest in the Solar System at 5.427&nbsp;g/cm³, only slightly less than Earth’s density of 5.515&nbsp;g/cm³.<ref name="nssdcMercury" /> If the effect of gravitational compression were to be factored out, the materials of which Mercury is made would be denser, with an uncompressed density of 5.3&nbsp;g/cm³ versus Earth’s 4.4&nbsp;g/cm³.<ref>{{cite web
| Author=staff | date=[[May 8]], [[2003]]
| url=http://astrogeology.usgs.gov/Projects/BrowseTheGeologicSolarSystem/MercuryBack.html
|title=Mercury
|publisher=U.S. Geological Survey
|accessdate=2006-11-26 }}</ref>


===Metallica controversy===
[[Image:Mercury Internal Structure.svg|thumb|left|250px|1. Crust&mdash;100–300&nbsp;km thick<br/>
Deathstars have recently made claim that that they were an inspiration on [[United States|American]] [[thrash metal]] band [[Metallica]]'s use of Deathstars' logotype font on the packaging of their 2008 album ''[[Death Magnetic]]'', and a song titled "Cyanide" appearing on the album (a song of the same name by Deathstars appeared on 2006's ''[[Termination Bliss]]''). In regards to this, an update on Deathstars' website ended with a joke that their third studio album would be titled ''Master of Muppets'', and would be available for free download on January 30, 2009. This title is a reference to Metallica's 1986 album ''[[Master of Puppets]]''.
2. Mantle&mdash;600&nbsp;km thick<br/>
3. Core&mdash;1,800&nbsp;km radius]]
Mercury’s density can be used to infer details of its inner structure. While the Earth’s high density results appreciably from gravitational compression, particularly at the [[planetary core|core]], Mercury is much smaller and its inner regions are not nearly as strongly compressed. Therefore, for it to have such a high density, its core must be large and rich in iron.<ref>{{cite journal
| title = On the Internal Structures of Mercury and Venus
| author = Lyttleton, R. A.
| journal = Astrophysics and Space Science
| volume = 5
| issue = 1
| pages = 18
| year = 1969
| accessdate = 2008-04-16
| url =
| doi = 10.1007/BF00653933 }}</ref> Geologists estimate that Mercury’s core occupies about 42% of its volume; for Earth this proportion is 17%. Recent research strongly suggests Mercury has a molten core.<ref name='cornell'>{{cite news
| first=Lauren | last=Gold
| title=Mercury has molten core, Cornell researcher shows
| date=[[May 3]], [[2007]] | publisher=Cornell University
| url =http://www.news.cornell.edu/stories/May07/margot.mercury.html
| work =Chronicle Online | accessdate =2008-05-12 }}</ref><ref name=nrao/>


Metallica have not responded to the claims posed by Deathstars, though it is likely the latter band does not take the "inspiration" they had seriously, as Whiplasher Bernadotte clarified, "It's just fun. What can I say, it's just as big of a coincidence and chance as if you get a [[hermaphrodite]]-child. What can you do..? You just need to smile at the little monster."
Surrounding the core is a 600&nbsp;km [[mantle (geology)|mantle]] consisted of silicates<ref>Gallant, R. 1986. ''The National Geographic Picture Atlas of Our Universe''. National Geographic Society, 2nd edition.</ref>. It is generally thought that early in Mercury’s history, a giant impact with a body several hundred kilometers across stripped the planet of much of its original mantle material, resulting in the relatively thin mantle compared to the sizable core.<ref name="Benz">
{{cite journal
| title = Collisional stripping of Mercury’s mantle
| author = Benz, W.; Slattery, W. L.; Cameron, A. G. W.
| journal = Icarus
| volume = 74
| issue = 3
| pages = 516–528
| year = 1988
| accessdate = 2008-04-16
| url =
| doi = 10.1016/0019-1035(88)90118-2 }}</ref>


==Track listing==
Based on data from the ''Mariner&nbsp;10'' mission and Earth-based observation, Mercury’s [[crust (geology)|crust]] is believed to be 100–300&nbsp;km thick.<ref name="anderson1">{{cite journal
===Confirmed working titles===
| author=J.D. Anderson, et al | title=Shape and Orientation of Mercury from Radar Ranging Data
* "Blood Stains Blondes"
| publisher=Jet Propulsion Laboratory, California Institute of Technology | date=[[July 10]], [[1996]]
* "Chertograd"
| doi=10.1006/icar.1996.0242 | journal=Icarus | volume=124 | pages=690 }}</ref> One distinctive feature of Mercury’s surface is the presence of numerous narrow ridges, some extending over several hundred kilometers. It is believed that these were formed as Mercury’s core and mantle cooled and contracted at a time when the crust had already solidified.<ref>{{cite journal
* "Night Electric Night"
| title = Lobate Thrust Scarps and the Thickness of Mercury’s Lithosphere
* "Opium"
| author = Schenk, P.; Melosh, H. J.;
* "Venus in Arms"
| journal = Abstracts of the 25th Lunar and Planetary Science Conference
| volume = 1994
| issue =
| pages = 1994LPI....25.1203S
| year =
| accessdate =2008-06-03
| url = http://adsabs.harvard.edu/abs/1994LPI....25.1203S
| doi = }}
</ref><!-- CHRONOLOGY OF LOBATE SCARP THRUST FAULTS AND THE MECHANICAL STRUCTURE OF
MERCURY’S LITHOSPHERE T. R. Watters , F. Nimmo and M. S. Robinson http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1886.pdf OR Geology; November 1998; v. 26; no. 11; p. 991-994, Topography of lobate scarps on Mercury; new constraints on the planet's contraction Thomas R. Watters, Mark S. Robinson, and Anthony C. Cook OR might be the better refs-->


==Personnel==
Mercury's core has a higher iron content than that of any other major planet in the Solar System, and several theories have been proposed to explain this. The most widely accepted theory is that Mercury originally had a metal-silicate ratio similar to common [[chondrite]] meteors, thought to be typical of the Solar System's rocky matter, and a mass approximately 2.25 times its current mass.<ref name="Benz" /> However, early in the solar system’s history, Mercury may have been struck by a [[planetesimal]] of approximately 1/6 that mass.<ref name="Benz" /> The impact would have stripped away much of the original crust and mantle, leaving the core behind as a relatively major component.<ref name="Benz" /> A similar process has been proposed to explain the formation of Earth’s [[Moon]] (''see [[giant impact theory]]'').<ref name="Benz" />
* [[Andreas Bergh|Whiplasher Bernadotte]] – [[Singing|vocals]]

* [[Emil Nödtveidt|Nightmare Industries]] – [[guitar]]s, [[Keyboard instrument|keyboards]]
Alternatively, Mercury may have formed from the [[solar nebula]] before the Sun’s [[energy]] output had stabilized. The planet would initially have had twice its present mass, but as the [[protostar|protosun]] contracted, temperatures near Mercury could have been between 2&nbsp;500 and 3&nbsp;500&nbsp;K, (2&nbsp;227 °C to 3&nbsp;227 °C) and possibly even as high as 10&nbsp;000&nbsp;K (9&nbsp;727 °C).<ref name="CameronAGW1">
* [[Eric "Cat Casino" Bäckman|Cat Casino]] – guitars
{{cite journal | title = The partial volatilization of Mercury | author = Cameron, A. G. W. | journal = Icarus | volume = 64 | issue = 2| pages = 285–294 | year = 1985| accessdate = | url = | doi = 10.1016/0019-1035(85)90091-0 }}</ref> Much of Mercury’s surface rock could have been vaporized at such temperatures, forming an atmosphere of "rock vapor" which could have been carried away by the [[solar wind]].<ref name="CameronAGW1" />
* [[Jonas Kangur|Skinny Disco]] – [[Bass guitar|bass]], [[Backing vocalist|backing vocals]]

* [[Ole Öhman|Bone W. Machine]] – [[Drum kit|drums]]
A third hypothesis proposes that the [[solar nebula]] caused [[drag (physics)|drag]] on the particles from which Mercury was [[accretion (science)|accreting]], which meant that lighter particles were lost from the accreting material.<ref>{{cite journal
| title = Iron/silicate fractionation and the origin of Mercury
| author = Weidenschilling, S. J.
| journal = Icarus
| volume = 35
| issue = 1
| pages = 99–111
| year = 1987
| accessdate = 2008-04-16
| url =
| doi = 10.1016/0019-1035(78)90064-7}}</ref> Each of these hypotheses predicts a different surface composition, and two upcoming space missions, [[MESSENGER]] and [[BepiColombo]], both aim to make observations to test them.<ref name="MSGRgrayzeck">{{cite web| first=Ed | last=Grayzeck | url=http://messenger.jhuapl.edu/| title=MESSENGER Web Site | publisher=Johns Hopkins University |accessdate=2008-04-07 }}</ref><ref name="ESA pages">{{cite web| url=http://sci.esa.int/science-e/www/area/index.cfm?fareaid=30| title=BepiColombo | work=ESA Science & Technology| publisher=European Space Agency| accessdate=2008-04-07 }}</ref>

==Surface geology==
[[Image:Mercury in color c1000 700 430.png|thumb|right|First high-resolution image of Mercury transmitted by MESSENGER (false color)]]
[[Image:CW0131775256F Kuiper Crater.png|thumb|right|Image from MESSENGER's second Mercury flyby. [[Kuiper (crater on Mercury)|Kuiper crater]] is just below center. An extensive [[ray system]] emanates from the [[Impact crater|crater]] near the top.]]
{{main|Geology of Mercury}}
Mercury’s surface is overall very similar in appearance to that of the Moon, showing extensive [[Lunar mare|mare]]-like plains and heavy cratering, indicating that it has been geologically inactive for billions of years. Since our knowledge of [[geology of Mercury|Mercury's geology]] has been based on the 1975 [[#Mariner 10|Mariner]] flyby and [[#Ground-based telescopic research|terrestrial]] observations, it is the least understood of the terrestrial planets.<ref name=nrao>{{cite news
| last=Finley | first=Dave | date=[[May 3]], [[2007]]
| title=Mercury's Core Molten, Radar Study Shows
| publisher=National Radio Astronomy Observatory
| url=http://www.nrao.edu/pr/2007/mercury/
| accessdate=2008-05-12 }}</ref> As data from the recent [[#MESSENGER|MESSENGER]] flyby is processed this knowledge will increase. For example, an unusual crater with radiating troughs has been discovered which scientists are calling "the spider."<ref>{{cite news
| author=Staff | title=Scientists see Mercury in a new light
| url=http://www.sciencedaily.com/releases/2008/02/080201093149.htm
| publisher=Science Daily | date=[[February 28]], [[2008]]
| accessdate=2008-04-07 }}</ref>

[[Albedo]] features refer to areas of markedly different reflectivity, as seen by telescopic observation. Mercury also possesses [[Dorsum|Dorsa]] (also called "[[wrinkle-ridge]]s"), Moon-like [[Highland (geography)|highlands]], Montes (mountains), [[Planitia]]e, or plains, [[Rupes]] ([[escarpments]]), and [[Vallis|Valles]] ([[valleys]]).<ref>{{cite web | last=Blue | first=Jennifer | date=[[April 11]], [[2008]] | url=http://planetarynames.wr.usgs.gov/ | title=Gazetteer of Planetary Nomenclature | publisher=US Geological Survey | accessdate=2008-04-11 }}</ref><ref name="DunneCh7">{{cite book|title=The Voyage of Mariner&nbsp;10 — Mission to Venus and Mercury|author=Dunne, J. A. and Burgess, E.|chapterurl=http://history.nasa.gov/SP-424/ch7.htm|publisher=NASA History Office|year=1978|chapter=Chapter Seven|url=http://history.nasa.gov/SP-424/|accessdate=2008-05-28}}</ref>

Mercury was heavily bombarded by [[comet]]s and [[asteroid]]s during and shortly following its formation 4.6 billion years ago, as well as during a possibly separate subsequent episode called the [[late heavy bombardment]] that came to an end 3.8 billion years ago.<ref>{{cite journal|author=Strom, Robert|month=September | year=1979|volume=Volume 24|title=Mercury: a post-Mariner assessment|journal=Space Science Review|pages=pp. 3–70}}</ref> During this period of intense crater formation, the planet received impacts over its entire surface,<ref name="DunneCh7" /> facilitated by the lack of any [[Celestial body atmosphere|atmosphere]] to slow impactors down.<ref>{{cite journal|last=Broadfoot|first=A. L.|coauthors=S. Kumar, M. J. S. Belton, and M. B. McElroy|title=Mercury's Atmosphere from Mariner&nbsp;10: Preliminary Results|journal=Science|volume=Vol. 185|issue=No. 4146|date=[[July 12]], [[1974]] |pages=pp.166–169|doi=10.1126/science.185.4146.166|pmid=17810510}}</ref> During this time the planet was [[volcano|volcanically]] active; basins such as the [[Caloris Basin]] were filled by [[magma]] from within the planet, which produced smooth plains similar to the [[Lunar mare|maria]] found on the Moon.<ref>{{cite web
| author=Staff
| date=[[August 5]], [[2003]]
| url=http://astrogeology.usgs.gov/Projects/BrowseTheGeologicSolarSystem/MercuryBack.html
| title=Mercury
| publisher=U.S. Geological Survey
| accessdate=2008-04-07 }}
</ref><ref>{{cite journal
| last=Head | first=James W.
| coauthors=Solomon, Sean C.
| title=Tectonic Evolution of the Terrestrial Planets
| journal=Science
| year=1981 | volume=213
| issue=4503 | pages=62–76
| url=http://www.sciencemag.org/cgi/content/abstract/213/4503/62
| doi=10.1126/science.213.4503.62
| accessdate=2008-04-07
| pmid=17741171 }}</ref>

===Impact basins and craters===
[[Image:Caloris basin labeled.png|thumb|left|200px|Mercury’s [[Caloris Basin]] is one of the largest impact features in the Solar System.]]
[[Impact crater|Crater]]s on Mercury range in diameter from small bowl-shaped cavities to multi-ringed [[impact basin]]s hundreds of kilometers across. They appear in all states of degradation, from relatively fresh rayed craters to highly degraded crater remnants. Mercurian craters differ subtly from lunar craters in that the area blanketed by their ejecta is much smaller, a consequence of Mercury's stronger surface gravity.<ref name=Spudis01>{{cite journal
| first=P. D. | last=Spudis | title=The Geological History of Mercury
| journal=Workshop on Mercury: Space Environment, Surface, and Interior, Chicago
| year=2001 |pages=100 | url=http://adsabs.harvard.edu/abs/2001mses.conf..100S | accessdate=2008-06-03 }}</ref>

The largest known craters are Caloris Basin, with a diameter of 1550&nbsp;km,<ref name="newscientist30012008">{{cite news
| url=http://space.newscientist.com/article/dn13257-bizarre-spider-scar-found-on-mercurys-surface.html
| title=Bizarre spider scar found on Mercury's surface
| date= [[January 30]], [[2008]] | publisher= NewScientist.com news service
| first= David
| last= Shiga}}</ref> and the [[Skinakas Basin]] with an outer-ring diameter of 2300&nbsp;km.<ref name=Ksa06>{{cite journal|author = L. V. Ksanfomality|title=Earth-based optical imaging of Mercury| journal= Advances in Space Research |volume= 38|pages= 594|year= 2006|url= http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006AdSpR..38..594K&amp;db_key=AST&amp;data_type=HTML&amp;format=&amp;high=461152a03222956|doi=10.1016/j.asr.2005.05.071}}</ref> The impact that created the Caloris Basin was so powerful that it caused [[lava]] eruptions and left a concentric ring over 2&nbsp;km tall surrounding the [[impact crater]]. At the [[antipodes|antipode]] of the Caloris Basin is a large region of unusual, hilly terrain known as the "Weird Terrain". One hypothesis for its origin is that shock waves generated during the Caloris impact traveled around the planet, converging at the basin’s antipode (180 degrees away). The resulting high stresses fractured the surface.<ref>{{cite journal
|last=Schultz
|first=Peter H.
|authorlink=
|coauthors=Gault, Donald E.
|year=1975
|month=
|title=Seismic effects from major basin formations on the moon and Mercury
|journal=Earth, Moon, and Planets
|volume=12
|issue= 2
|pages=159–175
|id=
|doi = 10.1007/BF00577875
|url=http://adsabs.harvard.edu/abs/1975Moon...12..159S
|accessdate=2008-04-16
}}</ref> Alternatively, it has been suggested that this terrain formed as a result of the convergence of ejecta at this basin’s antipode.<ref>{{cite journal
| last=Wieczorek | first=Mark A. | coauthors=Zuber, Maria T.
| title=A Serenitatis origin for the Imbrian grooves and South Pole-Aitken thorium anomaly
| journal=Journal of Geophysical Research
| year=2001 | volume=106 | issue=E11 | pages=27853–27864
| url=http://www.agu.org/pubs/crossref/2001/2000JE001384.shtml
| accessdate=2008-05-12
| doi=10.1029/2000JE001384 }}</ref>

Overall, about 15 impact basins have been identified on the imaged part of Mercury. Other notable basins include the 400 km wide, multi-ring, [[Tolstoj Basin]] which has an ejecta blanket extending up to 500 km from its rim, and its floor has been filled by smooth plains materials. [[Beethoven Basin]] also has a similar-sized ejecta blanket and a 625 km diameter rim.<ref name=Spudis01/> Like the [[Moon]], the surface of Mercury has likely incurred the effects of [[space weathering]] processes, including [[Solar wind]] and [[micrometeorite]] impacts.<ref>{{cite journal
| title=Albedo of Immature Mercurian Crustal Materials: Evidence for the Presence of Ferrous Iron
| journal=Lunar and Planetary Science | volume=39 | year=2008 | pages=1750
| last=Denevi | first=B. W. | coauthors=Robinson, M. S.
| url=http://adsabs.harvard.edu/abs/2008LPI....39.1750D | accessdate=2008-06-03 }}</ref>

===Plains===
There are two geologically distinct plains regions on Mercury.<ref name=WagWolIva01>{{cite journal|author=R.J. Wagner ''et al.''|title=Application of an Updated Impact Cratering Chronology Model to Mercury's Time-Stratigraphic System|journal=Workshop on Mercury: Space Environment, Surface, and Interior, Chicago|year=2001|pages=106|url=http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001mses.conf..106W&amp;db_key=AST&amp;data_type=HTML&amp;format=&amp;high=4613707b1d22308}}</ref><ref name=Spudis01/> Gently rolling, hilly plains in the regions between craters are Mercury's oldest visible surfaces,<ref name=Spudis01/> predating the heavily cratered terrain. The inter-crater plains appear to have obliterated many earlier craters, and show a general paucity of smaller craters below about 30 km in diameter.<ref name=WagWolIva01/> It is not clear whether they are of volcanic or impact origin.<ref name=WagWolIva01/> The inter-crater plains are distributed roughly uniformly over the entire surface of the planet.
[[Image:Mercury's 'Weird Terrain'.jpg|thumb|right|200px|The so-called “Weird Terrain” was formed by the [[Caloris Basin]] impact at its antipodal point.]]

Smooth plains are widespread flat areas which fill depressions of various sizes and bear a strong resemblance to the lunar maria. Notably, they fill a wide ring surrounding the Caloris Basin. An appreciable difference between these plains and lunar maria is that the smooth plains of Mercury have the same albedo as the older inter-crater plains. Despite a lack of unequivocally volcanic characteristics, the localisation and rounded, lobate shape of these plains strongly support volcanic origins.<ref name=Spudis01/> All the Mercurian smooth plains formed significantly later than the Caloris basin, as evidenced by appreciably smaller crater densities than on the Caloris ejecta blanket.<ref name=Spudis01/> The floor of the [[Caloris Basin]] is also filled by a geologically distinct flat plain, broken up by ridges and fractures in a roughly polygonal pattern. It is not clear whether they are volcanic lavas induced by the impact, or a large sheet of impact melt.<ref name=Spudis01/>

One unusual feature of the planet’s surface is the numerous compression folds, or [[rupes]], which crisscross the plains. It is thought that as the planet’s interior cooled, it contracted and its surface began to deform. The folds can be seen on top of other features, such as craters and smoother plains, indicating that they are more recent.<ref>{{cite journal
|last=Dzurisin |first=D. |date=[[October 10]], [[1978]]
|title=The tectonic and volcanic history of Mercury as inferred from studies of scarps, ridges, troughs, and other lineaments
|journal=Journal of Geophysical Research
|volume=83 |pages=4883–4906
|url=http://adsabs.harvard.edu/abs/1978JGR....83.4883D |accessdate=2008-06-03
|doi=10.1029/JB083iB10p04883 }}</ref> Mercury’s surface is also flexed by significant [[tidal bulge]]s raised by the [[Sun]]—the Sun’s tides on Mercury are about 17 times stronger than the Moon’s on Earth.<ref>{{cite journal
|last=Van Hoolst |first=Tim |coauthors=Jacobs, Carla |year=2003
|title=Mercury’s tides and interior structure
|journal=Journal of Geophysical Research
|volume=108 |issue=E11 |pages=7
|doi=10.1029/2003JE002126 |accessdate=2008-04-16 }}</ref>

==Surface conditions and "atmosphere" (exosphere)==
The [[mean]] surface [[temperature]] of Mercury is 442.5 K,<ref name="nssdcMercury" /> but it ranges from 100 K to 700 K,<ref>{{cite book|author=Prockter, Louise|title=Ice in the Solar System|publisher=Johns Hopkins APL Technical Digest|volume=Volume 26|issue=number 2|year=2005}}</ref> due to the absence of an atmosphere. On the dark side of the planet, temperatures average 110 K.<ref>{{cite journal
| last=Murdock
| first=T. L.
| coauthors=Ney, E. P.
| title=Mercury: The Dark-Side Temperature
| journal=[[Science (journal)|Science]]
| year=1970
| volume=170
| issue=3957
| pages=535–537
| url=http://www.sciencemag.org/cgi/content/abstract/170/3957/535
| doi=10.1126/science.170.3957.535
| accessdate=2008-04-09
| pmid=17799708 }}</ref> The intensity of [[sunlight]] on Mercury’s surface ranges between 4.59 and 10.61 times the [[solar constant]] (1370Wm<sup><small>&minus;2</small></sup>).<ref>{{cite book|title=Physics and Chemistry of the Solar System|author=John S. Lewis|pages=461|publisher=Academic Press|year=2004|url=http://books.google.co.uk/books?id=ERpMjmR1ErYC&pg=RA1-PA461&lpg=RA1-PA461&dq=solar-constant+mercury+-wikipedia+-wiki+-encyclopedia&source=web&ots=5jprP6dXYk&sig=iJEN0OU01yxgxnZhPcG17z-exYw&hl=en#PRA1-PA461,M1
|accessdate=2008-06-03}}</ref>

[[Image:Merc fig2sm.jpg|thumb|left|Radar image of Mercury's north pole]]
Despite the generally extremely high temperature of its surface, observations strongly suggest that [[ice]] exists on Mercury. The floors of some deep craters near the poles are never exposed to direct sunlight, and temperatures there remain far lower than the global average. Water ice strongly reflects [[radar]], and observations by the 70m [[Goldstone Deep Space Communications Complex|Goldstone]] telescope and the [[Very Large Array|VLA]] in the early 1990s revealed that there are patches of very high radar [[reflection]] near the poles.<ref>{{cite journal |last=Slade
|first=MA
|authorlink=
|coauthors=Butler, BJ; Muhleman, DO
|year=1992
|month=
|title=Mercury radar imaging — Evidence for polar ice
|journal=[[Science (journal)|Science]]
|volume=258
|issue=5082
|pages=635–640
|doi=10.1126/science.258.5082.635
|url=
|accessdate=2008-04-16
|quote=
|pmid=17748898 }}</ref> While ice is not the only possible cause of these reflective regions, astronomers believe it is the most likely.<ref>{{cite web
| last=Williams | first=David R. | date=[[June 2]], [[2005]]
| url=http://nssdc.gsfc.nasa.gov/planetary/ice/ice_mercury.html
| title=Ice on Mercury
| publisher=NASA Goddard Space Flight Center
| accessdate=2008-05-23 }}</ref>

The icy regions are believed to be covered to a depth of only a few meters, and contain about 10<sup>14</sup>–10<sup>15</sup>&nbsp;kg of ice.<ref name="Zahnle1">{{cite journal
|last=Rawlins |first=K
|authorlink=
|coauthors=Moses, JI; Zahnle, KJ
|year=1995
|month=
|title=Exogenic Sources of Water for Mercury's Polar Ice
|journal=Bulletin of the American Astronomical Society
|volume=27
|bibcode=1995DPS....27.2112R
|pages=1117
|id=
|url=
|accessdate=
|quote= }}</ref> By comparison, the [[Antarctica|Antarctic]] ice sheet on Earth has a mass of about 4{{e|18}}&nbsp;kg, and [[Mars]]’ south polar cap contains about 10<sup>16</sup>&nbsp;kg of water.<ref name="Zahnle1" /> The origin of the ice on Mercury is not yet known, but the two most likely sources are from [[outgassing]] of water from the planet’s interior or deposition by impacts of [[comet]]s.<ref name="Zahnle1" />

[[Image:Terrestrial planet size comparisons.jpg|thumb|right|300px|Size comparison of terrestrial planets (left to right): Mercury, [[Venus]], [[Earth]], and [[Mars]]]]

Mercury is too small for its [[gravity]] to retain any significant [[atmosphere]] over long periods of time; however, it does have a "tenuous surface-bounded [[exosphere]]"<ref> [http://adsabs.harvard.edu/abs/2007SSRv..131..161D Mercury's Atmosphere: A Surface-Bounded Exosphere] Publication: Space Science Reviews, Volume 131, Issue 1-4, pp. 161-186 Publication Date: 08/2007 DOI: 10.1007/s11214-007-9260-9</ref> containing [[hydrogen]], [[helium]], [[oxygen]], [[sodium]], [[calcium]] and [[potassium]]. This exosphere is not stable—atoms are continuously lost and replenished from a variety of sources. Hydrogen and helium atoms probably come from the [[solar wind]], [[diffusion|diffusing]] into Mercury’s magnetosphere before later escaping back into space. [[Radioactive decay]] of elements within Mercury’s crust is another source of helium, as well as sodium and potassium. Water vapor is present, being brought to Mercury by some combination of processes such as: comets striking its surface, [[sputtering]] creating water "where none existed before from the ingredients of [[solar wind]] and Mercury rock" (both contain hydrogen and oxygen), and "reservoirs of water ice in small areas of Mercury's poles where local topography creates permanently shadowed spots in crater walls that might trap water over the age of the solar system". [[MESSENGER]] found high proportions of calcium, helium, hydroxide, magnesium, oxygen, potassium, silicon, sodium, and water. The detection of high amounts of water-related ions like O+, OH-, and H2O+ was a surprise.<ref>Hunten, D. M.; Shemansky, D. E.; Morgan, T. H.; ''The Mercury atmosphere'', In: Mercury (A89-43751 19-91). University of Arizona Press (1988), pp. 562–612</ref><ref> [http://www.planetary.org/news/2008/0703_MESSENGER_Scientists_Astonished_to.html Planetary News: Mercury] July 3, 2008</ref> Because of the quantities of these ions that were detected in Mercury's space environment, scientists surmise that these molecules were blasted from the surface or exosphere by the solar wind.<ref>[http://newswise.com/articles/view/542209/ Instrument Shows What Planet Mercury Is Made Of] Newswise, Retrieved on July 6, 2008.</ref>

Sodium and potassium were discovered in the atmosphere during the 1980s, and are believed to result primarily from the vaporization of surface rock struck by micrometeorite impacts. Due to the ability of these materials to diffuse sunlight, Earth-based observers can readily detect their composition in the atmosphere. Studies indicate that, at times, sodium emissions are localized at points that correspond to the planet's magnetic dipoles. This would indicate some interaction between the magnetosphere and the planet's surface.<ref name="chaikin1" />

==Magnetic field and magnetosphere==
[[Image:Mercury Magnetic Field NASA.jpg|thumb|left|200px|Graph showing relative strength of Mercury's magnetic field]]
Despite its small size and slow 59-day-long rotation, Mercury has a significant, and apparently global, [[magnetic field]]. According to measurements taken by Mariner&nbsp;10, it is about 1.1% as strong as the Earth’s. The magnetic field strength at the Mercurian equator is about 300&nbsp;[[Tesla (unit)|nT]].<ref>{{cite book
| title=Astronomy: The Solar System and Beyond
| first=Michael A. | last=Seeds | year=2004
| isbn=0534421113 | publisher=Brooks Cole
| edition=4th
}}</ref><ref>{{cite web
| last=Williams | first=David R. | date=[[January 6]], [[2005]]
| url=http://nssdc.gsfc.nasa.gov/planetary/planetfact.html
| title=Planetary Fact Sheets
| publisher=NASA National Space Science Data Center
| accessdate=2006-08-10 }}</ref> Like that of Earth, Mercury's magnetic field is [[dipole|dipolar]] in nature.<ref name="chaikin1">{{cite book
| first=J. Kelly | last=Beatty | coauthors=Petersen, Carolyn Collins; Chaikin, Andrew
| title=The New Solar System | year=1999
| publisher=Cambridge University Press | isbn=0521645875 }}</ref> Unlike Earth, however, Mercury's poles are nearly aligned with the planet's spin axis.<ref name="qq">{{cite web
| author=Staff | date=[[January 30]], [[2008]]
| url=http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?page=2&gallery_id=2&image_id=152
| title=Mercury’s Internal Magnetic Field
| publisher=NASA | accessdate=2008-04-07}}</ref> Measurements from both the Mariner&nbsp;10 and MESSENGER space probes have indicated that the strength and shape of the magnetic field are stable.<ref name="qq" />

It is likely that this magnetic field is generated by way of a [[Dynamo theory|dynamo]] effect, in a manner similar to the magnetic field of Earth.<ref>{{cite web
| last=Gold
| first=Lauren
| date=[[May 3]], [[2007]]
| url=http://www.news.cornell.edu/stories/May07/margot.mercury.html
| title=Mercury has molten core, Cornell researcher shows
| publisher=Cornell University
| accessdate=2008-04-07}}</ref><ref>{{cite journal
| last=Christensen| first=Ulrich R.
| title=A deep dynamo generating Mercury's magnetic field
| journal=Nature
| year=2006
| volume=444
| issue=
| pages=1056–1058
| doi=10.1038/nature05342}}</ref> This dynamo effect would result from the circulation of the planet's iron-rich liquid core. Particularly strong tidal effects caused by the planet's high orbital eccentricity would serve to keep the core in the liquid state necessary for this dynamo effect.<ref>{{cite journal
| last=Spohn | first=T.
| coauthors=Sohl, F.; Wieczerkowski, K.; Conzelmann, V.
| title=The interior structure of Mercury: what we know, what we expect from BepiColombo
| journal=Planetary and Space Science | year=2001
| volume=49 | issue=14–15 | pages=1561–1570
| doi=10.1016/S0032-0633(01)00093-9 }}</ref>

Mercury’s magnetic field is strong enough to deflect the [[solar wind]] around the planet, creating a [[magnetosphere]]. The planet's magnetosphere, though small enough to fit within the Earth,<ref name="chaikin1" /> is strong enough to trap solar wind plasma. This contributes to the [[space weathering]] of the planet's surface.<ref name="qq" /> Observations taken by the Mariner&nbsp;10 spacecraft detected this low energy plasma in the magnetosphere of the planet's nightside. Bursts of energetic particles were detected in the planet's magnetotail, which indicates a dynamic quality to the planet's magnetosphere.<ref name="chaikin1" />

==Orbit and rotation==
[[Image:ThePlanets Orbits Mercury PolarView.svg|left|thumb|230px|Orbit of Mercury (yellow)]]
Mercury has the most [[Orbital eccentricity|eccentric]] orbit of all the planets; its eccentricity is 0.21 with its distance from the Sun ranging from 46 to 70 million kilometers. It takes 88 days to complete an orbit.
The diagram on the left illustrates the effects of the eccentricity, showing Mercury’s orbit overlaid with a circular orbit having the same [[semi-major axis]]. The higher velocity of the planet when it is near perihelion is clear from the greater distance it covers in each 5-day interval. The size of the spheres, inversely proportional to their distance from the Sun, is used to illustrate the varying heliocentric distance. This varying distance to the Sun, combined with a 3:2 [[Mercury (planet) #Spin–orbit resonance|spin-orbit resonance]] of the planet’s rotation around its axis, result in complex variations of the surface temperature.<ref name=strom>{{cite book
| first=Robert G. | last=Strom
| coauthors=Sprague, Ann L. | year=2003
| title=Exploring Mercury: the iron planet
| publisher=Springer | isbn=1852337311 }}</ref>

Mercury’s orbit is inclined by 7° to the plane of Earth’s orbit (the [[ecliptic]]), as shown in the diagram on the right. As a result, [[Transit of Mercury|transit]]s of Mercury across the face of the Sun can only occur when the planet is crossing the plane of the ecliptic at the time it lies between the Earth and the Sun. This occurs about every seven years on average.<ref>{{cite web
| last=Espenak | first=Fred | date=[[April 21]], [[2005]]
| url=http://eclipse.gsfc.nasa.gov/transit/catalog/MercuryCatalog.html
| title=Transits of Mercury
| publisher=NASA/Goddard Space Flight Center
| accessdate=2008-05-20 }}</ref>

[[Image:ThePlanets Orbits Mercury EclipticView.svg|right|thumb|230px|Orbit of Mercury as seen from the ascending node (bottom) and from 10° above (top)]]
Functionally, Mercury’s [[axial tilt]] is nonexistent,<ref name="JPLweather">{{cite web|url=http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=725|title=Weather, Weather, Everywhere?|author=Samantha Harvey|publisher=[[NASA]] Jet Propulsion Laboratory|date=[[April 24]], [[2008]] |accessdate=2008-05-23}}</ref><ref name="Cosmic1">{{cite book|title=Cosmic Perspectives in Space Physics|author=S. Biswas|publisher=Springer|year=2000|pages=176}}</ref> with measurements as low as 0.027°.<ref name=Margot2007/> This is significantly smaller than that of Jupiter, which boasts the second smallest axial tilt of all planets at 3.1 degrees. This means an observer at Mercury’s equator during local noon would never see the Sun more than approximately 1/30{{Ref_label|A|a|none}} of one degree north or south of the [[zenith]]. Conversely, at the poles the Sun never rises more than 2.1′ above the horizon.<ref name=Margot2007/>

At certain points on Mercury’s surface, an observer would be able to see the Sun rise about halfway, then reverse and set before rising again, all within the same Mercurian day. This is because approximately four days prior to [[perihelion]], Mercury’s angular [[orbital velocity]] exactly equals its angular [[rotational velocity]] so that the Sun’s [[apparent motion]] ceases; at perihelion, Mercury’s angular orbital velocity then exceeds the angular rotational velocity. Thus, the Sun appears to move in a [[retrograde motion|retrograde]] direction. Four days after perihelion, the Sun’s normal apparent motion resumes at these points.<ref name="strom" />

===Advance of perihelion===
{{main|Tests of general relativity#Perihelion_precession_of_Mercury|Perihelion precession of Mercury}}
During the 19th century, French [[mathematician]] [[Le Verrier]] noticed that the slow [[precession]] of Mercury’s orbit around the Sun could not be completely explained by [[Newtonian mechanics]] and perturbations by the known planets. He proposed that another planet might exist in an orbit even closer to the Sun to account for this perturbation. (Other explanations considered included a slight oblateness of the Sun.) The success of the search for [[Neptune]] based on its perturbations of the orbit of [[Uranus]] led astronomers to place great faith in this explanation, and the hypothetical planet was even named [[Vulcan (hypothetical planet)|Vulcan]]. However, no such planet was ever found.<ref>{{cite book
| first=Richard | last=Baum |coauthors=Sheehan, William
| title = In Search of Planet Vulcan, The Ghost in Newton's Clockwork Machine
| year = 1997 | isbn=0-306-45567-6 }}</ref>

In the early 20th century, [[Albert Einstein]]’s [[General relativity|General Theory of Relativity]] provided the explanation for the observed precession. The effect is very small: the Mercurian relativistic perihelion advance excess is just 42.98 [[arcsecond]]s per century, therefore it requires a little over twelve million orbits for a full excess turn. Similar, but much smaller effects, operate for other planets, being 8.62 arcseconds per century for Venus, 3.84 for Earth, 1.35 for Mars, and 10.05 for [[1566 Icarus]].<ref>{{cite journal
| last=Gilvarry | first=J. J.
| title=Relativity Precession of the Asteroid Icarus
| journal=Physical Review
| year=1953 | volume=89 | issue=5 | pages=1046
| doi=10.1103/PhysRev.89.1046
| url=http://prola.aps.org/abstract/PR/v89/i5/p1046_1
| accessdate=2008-05-22
| format=subscription required }}
</ref><ref>{{cite web
| author=Anonymous
| url=http://www.mathpages.com/rr/s6-02/6-02.htm
| title=6.2 Anomalous Precession
| work=Reflections on Relativity
| publisher=MathPages | accessdate=2008-05-22 }}</ref>

[[Image:Mercury's orbital resonance.svg|thumb|right|200px|After one orbit, Mercury has rotated 1.5 times, so after two complete orbits the same hemisphere is again illuminated.]]

===Spin–orbit resonance===
For many years it was thought that Mercury was synchronously [[tidal locking|tidally locked]] with the Sun, [[rotation|rotating]] once for each orbit and keeping the same face directed towards the Sun at all times, in the same way that the same side of the Moon always faces the Earth. However, [[radar]] observations in 1965 proved that the planet has a 3:2 spin–orbit resonance, rotating three times for every two revolutions around the Sun; the eccentricity of Mercury’s orbit makes this resonance stable—at perihelion, when the solar tide is strongest, the Sun is nearly still in Mercury’s sky.<ref>{{cite journal
| last=Liu | first=Han-Shou | coauthors=O'Keefe, John A.
| title=Theory of Rotation for the Planet Mercury
| journal=Science | year=1965 | volume=150
| issue=3704 | pages=1717
| doi=10.1126/science.150.3704.1717
| pmid=17768871 }}</ref>

The original reason astronomers thought it was synchronously locked was that whenever Mercury was best placed for observation, it was always nearly at the same point in its 3:2 resonance, hence showing the same face. This is because, coincidentally, Mercury's rotation period is almost exactly half of its synodic period with respect to Earth. Due to Mercury’s 3:2 spin–orbit resonance, a [[solar day]] (the length between two [[meridian (astronomy)|meridian]] [[Astronomical transit|transit]]s of the Sun) lasts about 176 Earth days.<ref name="strom" /> A [[sidereal day]] (the period of rotation) lasts about 58.7 Earth days.<ref name="strom" />

Orbital simulations indicate that the eccentricity of Mercury’s orbit varies [[chaos theory|chaotically]] from 0 (circular) to a very high 0.47 over millions of years.<ref name="strom" /> This is thought to explain Mercury’s 3:2 spin-orbit resonance (rather than the more usual 1:1), since this state is more likely to arise during a period of high eccentricity.<ref name="Correia">{{cite journal
| last=Correia | first=Alexandre C. M.
| coauthors=Laskar, Jacques | year=2004
| title=Mercury’s capture into the 3/2 spin–orbit resonance as a result of its chaotic dynamics
| journal=[[Nature (journal)|Nature]] | volume=429
| pages=848–850 | doi=10.1038/nature02609 }}</ref>

==Observation==
Mercury’s [[apparent magnitude]] varies between about −2.0—brighter than [[Sirius]]—and 5.5.<ref name=ephemeris>{{cite web
| last=Espenak | first=Fred | date=[[July 25]], [[1996]]
| url=http://eclipse.gsfc.nasa.gov/TYPE/mercury2.html
| title=Twelve Year Planetary Ephemeris: 1995&ndash;2006
| work=NASA Reference Publication 1349
| publisher=NASA | accessdate=2008-05-23 }}</ref> Observation of Mercury is complicated by its proximity to the Sun, as it is lost in the Sun’s glare for much of the time. Mercury can be observed for only a brief period during either morning or evening twilight. The [[Hubble Space Telescope]] cannot observe Mercury at all, due to safety procedures which prevent its pointing too close to the Sun.<ref>{{cite journal
| last=Baumgardner | first=Jeffrey
| coauthors=Mendillo, Michael; Wilson, Jody K.
| title=A Digital High-Definition Imaging System for Spectral Studies of Extended Planetary Atmospheres. I. Initial Results in White Light Showing Features on the Hemisphere of Mercury Unimaged by ''Mariner'' 10
| journal=The Astronomical Journal | year=2000 | volume=119
| pages=2458&ndash;2464 | doi=10.1086/301323 }}</ref>

Like the Moon, Mercury exhibits [[Lunar phase|phases]] as seen from Earth, being "new" at [[Conjunction (astronomy and astrology)#Superior and inferior|inferior conjunction]] and “full” at [[Conjunction (astronomy and astrology)#Superior and inferior|superior conjunction]]. The planet is rendered invisible on both of these occasions by virtue of its rising and setting in concert with the Sun in each case. The first and last quarter phases occur at greatest [[Elongation (astronomy)|elongation]] east and west, respectively, when Mercury's separation from the Sun ranges anywhere from 17.9° at [[perihelion]] to 27.8° at [[aphelion]].<ref name=elongation>{{cite web
|title=Mercury Chaser's Calculator
|publisher=Fourmilab Switzerland
|author=John Walker
|url=http://www.fourmilab.ch/images/3planets/elongation.html
|accessdate=2008-05-29}} (look at 1964 and 2013)</ref><ref name=MercHorizons>{{cite web
|title=Mercury Elognation and Distance
|url=http://home.comcast.net/~kpheider/Mercury.txt
|accessdate=2008-05-30}} &mdash;Numbers generated using the Solar System Dynamics Group, [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=mb&sstr=1 Horizons On-Line Ephemeris System].</ref> At greatest elongation west, Mercury rises earliest before the Sun, and at greatest elongation east, it sets latest after the Sun.<ref name="RASC2007">{{cite book|title=Observer's Handbook 2007|author=Patrick Kelly, ed.|publisher=[[Royal Astronomical Society of Canada]]|year=2007|isbn=0-9738109-3-9}}</ref>

Mercury attains inferior conjunction every 116 days on average,<ref name="nssdcMercury" /> but this interval can range from 111 days to 121 days due to the planet’s eccentric orbit. Mercury can come as close as 77.3&nbsp;million km to the Earth,<ref name="nssdcMercury" /> but currently it does not come closer than 82&nbsp;million km from the Earth.<ref name=MercHorizons/> Its period of [[retrograde motion]] as seen from Earth can vary from 8 to 15 days on either side of inferior conjunction. This large range also arises from the planet’s high [[orbital eccentricity]].<ref name=strom />

Mercury is more often easily visible from Earth’s [[Southern Hemisphere]] than from its [[Northern Hemisphere]]; this is because its maximum possible elongations west of the Sun always occur when it is early autumn in the Southern Hemisphere, while its maximum possible eastern elongations happen when the Southern Hemisphere is having its late winter season.<ref name="RASC2007" /> In both of these cases, the angle Mercury strikes with the [[ecliptic]] is maximized, allowing it to rise several hours before the Sun in the former instance and not set until several hours after sundown in the latter in countries located at southern temperate zone latitudes, such as [[Argentina]] and [[New Zealand]].<ref name="RASC2007" /> By contrast, at northern temperate latitudes, Mercury is never above the horizon of a more-or-less fully dark night sky. Mercury can also, like several other planets and the brightest stars, be seen during a total [[solar eclipse]].<ref name=eclipse>{{cite web
|date=[[January 22]], [[2003]]
|title=Total Solar Eclipse of 2006 March 29
|publisher=Department of Physics at Fizik Bolumu in Turkey
|author=Tunç Tezel
|url=http://www.physics.metu.edu.tr/~aat/TSE2006/TSE2006.html
|accessdate=2008-05-24}}</ref>

Mercury is brightest as seen from Earth when it is at a [[gibbous phase]], between either quarter phase and full. Although the planet is further away from Earth when it is gibbous than when it is a crescent, the greater illuminated area visible more than compensates for the greater distance.<ref name=ephemeris/> The opposite is true for Venus, which appears brightest when it is a thin crescent, because it is much closer to Earth than when gibbous.<ref>{{cite web
| last=Espenak | first=Fred| year=1996
| url=http://sunearth.gsfc.nasa.gov/eclipse/TYPE/venus2.html
| title=NASA Reference Publication 1349; Venus: Twelve year planetary ephemeris, 1995&ndash;2006
| work=Twelve Year Planetary Ephemeris Directory
| publisher=NASA | accessdate=2008-05-24}}</ref>

==Studies of Mercury==
===Ancient astronomers===
The earliest known recorded observations of Mercury are from the [[MUL.APIN]] tablets. These observations were most likely made by an [[Assyria]]n astronomer around the 14th century BC.<ref>{{cite journal | title=The Latitude and Epoch for the Origin of the Astronomical Lore in MUL.APIN | first=Bradley E. | last=Schaefer | journal=American Astronomical Society Meeting 210, #42.05 | year=2007 | month=May | url=http://cdsads.u-strasbg.fr/abs/2007AAS...210.4205S | publisher=American Astronomical Society}}</ref> The [[Cuneiform script|cuneiform]] name used to designate Mercury on the MUL.APIN tablets is transcribed as UDU.IDIM.GU<sub>4</sub>.UD ("the jumping planet").{{Ref_label|B|b|none}}<ref>{{cite journal
| first=Hermann | last=Hunger |coauthors=Pingree, David
| title=MUL.APIN: An Astronomical Compendium in Cuneiform
| journal=Archiv für Orientforschung | volume=24
| publisher=Verlag Ferdinand Berger & Sohne Gesellschaft MBH
| location=Austria | year=1989 | pages=146 }}</ref> Babylonian records of Mercury date back to the 1st millennium BC. The Babylonians called the planet [[Nabu]] after the messenger to the Gods in their [[mythology]].<ref name="JHU history">{{cite web
| year=2008 | author=Staff
| url=http://btc.montana.edu/messenger/elusive_planet/ancient_cultures_2.php
| title=MESSENGER: Mercury and Ancient Cultures
| publisher=NASA JPL | accessdate=2008-04-07 }}</ref>

The [[Ancient Greece|ancient Greeks]] of [[Hesiod]]'s time knew the planet as Στίλβων (''Stilbon''), meaning "the gleaming", and Ἑρμάων (''Hermaon'').<ref>{{cite book |author= H.G. Liddell and R. Scott |coauthors=''rev.'' H.S. Jones and R. McKenzie |title=Greek–English Lexicon, with a Revised Supplement |edition=9th edition |year=1996 |publisher=Clarendon Press |location=Oxford |isbn=0-19-864226-1 |pages=pp 690 and 1646 }}</ref> Later Greeks called the planet [[Apollo (god)|Apollo]] when it was visible in the morning sky and [[Hermes]] when visible in the evening. Around the 4th century BC, however, Greek astronomers came to understand that the two names referred to the same body. The Romans named the planet after the Roman messenger god, [[Mercury (mythology)|Mercury]] (Latin ''Mercurius''), which they equated with the Greek [[Hermes]].<ref name="Dunne" /><ref>{{cite book
| first=Eugène Michel | last=Antoniadi
| coauthors=Translated from French by Moore, Patrick
| year=1974 | title=The Planet Mercury
| publisher=Keith Reid Ltd | location=Shaldon, Devon
| pages=pp 9&ndash;11 }}</ref>

In [[ancient China]], Mercury was known as Ch'en-Hsing, the Hour Star. It was associated with the direction north and the phase of water in the [[Wu Xing]].<ref>{{cite book
| first=David H. | last=Kelley
| coauthors=Milone, E. F.; Aveni, Anthony F. | year=2004
| title=Exploring Ancient Skies: An Encyclopedic Survey of Archaeoastronomy
| publisher=Birkhäuser | isbn=0387953108 }}</ref> [[Hindu mythology]] used the name [[Budha]] for Mercury, and this god was thought to preside over Wednesday.<ref>{{cite book
| first=R.M. | last=Pujari
| coauthors=Kolhe, Pradeep; Kumar, N. R. | year=2006
| title=Pride of India: A Glimpse Into India's Scientific Heritage
| publisher=Samskrita Bharati | isbn=8187276274 }}</ref> The god [[Odin]] (or Woden) of [[Germanic paganism]] was also associated with the planet Mercury and the name Wednesday was derived from Woden's day.<ref>{{cite book
| first=Michael E. | last=Bakich | year=2000
| title=The Cambridge Planetary Handbook
| publisher=Cambridge University Press
| isbn=0521632803 }}</ref> The [[Maya]] may have represented Mercury as an owl (or possibly four owls; two for the morning aspect and two for the evening) that served as a messenger to the [[underworld]].<ref>{{cite book
| first=Susan | last=Milbrath | year=1999
| title=Star Gods of the Maya: Astronomy in Art, Folklore and Calendars
| publisher=University of Texas Press
| isbn=0292752261 }}</ref>

===Ground-based telescopic research===
[[Image:Mercury transit 1.jpg|left|thumb|200px|[[Transit of Mercury]]. Mercury is the small dot in the lower center, in front of the sun. The dark area on the left of the solar disk is a sunspot.]]
The first [[telescope|telescopic]] observations of Mercury were made by [[Galileo]] in the early 17th century. Although he observed [[planetary phase|phases]] when he looked at Venus, his telescope was not powerful enough to see the phases of Mercury. In 1631 [[Pierre Gassendi]] made the first observations of the [[transit]] of a planet across the Sun when he saw a transit of Mercury predicted by [[Johannes Kepler]]. In 1639 [[Giovanni Battista Zupi|Giovanni Zupi]] used a telescope to discover that the planet had [[orbit]]al phases similar to Venus and the Moon. The observation demonstrated conclusively that Mercury orbited around the Sun.<ref name=strom/>

A very rare event in astronomy is the passage of one planet in front of another ([[occultation]]), as seen from Earth. Mercury and Venus occult each other every few centuries, and the event of [[May 28]] [[1737]] is the only one historically observed, having been seen by [[John Bevis]] at the [[Royal Greenwich Observatory]].<ref>{{cite journal |last=Sinnott |first=RW |authorlink= |coauthors=Meeus, J |year=1986 |month= |title=John Bevis and a Rare Occultation |journal=Sky and Telescope |volume=72 |issue= |pages=220 |id= |url=http://adsabs.harvard.edu/abs/1986S&T....72..220S |accessdate= |quote= }}</ref> The next occultation of Mercury by Venus will be on [[December 3]], [[2133]].<ref>{{cite book
| first=Timothy | last=Ferris | year=2003
| title=Seeing in the Dark: How Amateur Astronomers
| publisher=Simon and Schuster
| isbn=0684865807 }}</ref>

The difficulties inherent in observing Mercury mean that it has been far less studied than the other planets. In 1800 [[Johann Schröter]] made observations of surface features, claiming to have observed 20&nbsp;km high mountains. [[Friedrich Bessel]] used Schröter's drawings to erroneously estimate the rotation period as 24 hours and an axial tilt of 70°.<ref>{{cite journal
| last=Colombo | first=G. | coauthors=Shapiro, I. I.
| title=The Rotation of the Planet Mercury
| journal=SAO Special Report #188R
| url=http://adsabs.harvard.edu/abs/1965SAOSR.188.....C
| accessdate=2008-05-23 }}</ref> In the 1880s [[Giovanni Schiaparelli]] mapped the planet more accurately, and suggested that Mercury’s rotational period was 88 days, the same as its orbital period due to [[tidal locking]].<ref>{{cite journal
|last=Holden |first=E. S. |year=1890
|title=Announcement of the Discovery of the Rotation Period of Mercury [by Professor Schiaparelli]
|journal=Publications of the Astronomical Society of the Pacific |volume=2 |issue=7 |pages=79
|url=http://adsabs.harvard.edu/abs/1890PASP....2...79H |accessdate=2008-06-03
|doi=10.1086/120099 }}</ref> This phenomenon is known as [[synchronous rotation]] and is also shown by Earth’s Moon. The effort to map the surface of Mercury was continued by [[Eugenios Antoniadi]], who published a book in 1934 that included both maps and his own observations.<ref name="chaikin1" /> Many of the planet's surface features, particularly the [[List of albedo features on Mercury|albedo features]], take their names from Antoniadi's map.<ref>{{cite book|url=http://history.nasa.gov/SP-423/sp423.htm|title=Atlas of Mercury|publisher=[[NASA]] Office of Space Sciences|author=Merton E. Davies, et al|year=1978|chapter=Surface Mapping|chapterurl=http://history.nasa.gov/SP-423/surface.htm|accessdate=2008-05-28}}</ref>

In June 1962 [[Soviet Union|Soviet]] scientists at the [[Institute of Radio-engineering and Electronics]] of the [[USSR Academy of Sciences]] lead by [[Vladimir Kotelnikov]] became first to bounce [[radar]] signal off Mercury and receive it, starting radar observations of the planet.<ref>{{cite journal
|first= J. V. |last=Evans
| coauthors=Brockelman, R. A.; Henry, J. C.; Hyde, G. M.; Kraft, L. G.; Reid, W. A.; Smith, W. W.
| title=Radio Echo Observations of Venus and Mercury at 23 cm Wavelength
| year=1965 | journal=Astronomical Journal | volume=70
| url=http://articles.adsabs.harvard.edu/abs/1965AJ.....70..486E/0000487.000.html
| pages=487&ndash;500 | accessdate=2008-05-23
| doi=10.1086/109772 }}</ref><ref>{{cite book
| last=Moore | first=Patrick
| title=The Data Book of Astronomy | page=483 | year=2000
| publisher=CRC Press | location=New York
| url=http://books.google.com/books?lr=&as_brr=3&q=kotelnikov+1962+mercury&btnG=Search+Books
| isbn=0750306203}}</ref><ref>{{cite book
| title=To See the Unseen: A History of Planetary Radar Astronomy
| url=http://history.nasa.gov/SP-4218/sp4218.htm
| first=Andrew J. | last=Butrica
| publisher=[[NASA]] History Office, Washington D.C.
| year=1996 | chapter=Chapter 5
| chapterurl=http://history.nasa.gov/SP-4218/ch5.htm }}</ref> Three years later radar observations by Americans [[Gordon Pettengill]] and R. Dyce using 300-meter [[Arecibo Observatory]] [[radio telescope]] in [[Puerto Rico]] showed conclusively that the planet’s rotational period was about 59 days.<ref>{{cite journal
| last=Pettengill | first=G. H. |coauthors=Dyce, R. B.
| title=A Radar Determination of the Rotation of the Planet Mercury
| journal=[[Nature (journal)|Nature]] | volume=206
| issue= 1240 | pages= 451–2 | year= 1965
|doi=10.1038/2061240a0 }}</ref><ref>[http://scienceworld.wolfram.com/astronomy/Mercury.html Mercury] at Eric Weisstein's 'World of Astronomy'</ref> The theory that Mercury’s rotation was synchronous became widely held, and it was a surprise to astronomers when these radio observations were announced. If Mercury were tidally locked, its dark face would be extremely cold, but measurements of radio emission revealed that it was much hotter than expected. Astronomers were reluctant to drop the synchronous rotation theory and proposed alternative mechanisms such as powerful heat-distributing winds to explain the observations.<ref>{{cite book
| first=Bruce C. | last=Murray
| coauthors=Burgess, Eric | year=1977
| title=Flight to Mercury
| publisher=Columbia University Press
| isbn=0231039964 }}</ref>

Italian astronomer [[Giuseppe Colombo]] noted that the rotation value was about two-thirds of Mercury’s orbital period, and proposed that a different form of tidal locking had occurred in which the planet’s orbital and rotational periods were locked into a 3:2 rather than a 1:1 resonance.<ref>{{cite journal
| last=Colombo | first=G. | title=Rotational Period of the Planet Mercury
| journal=Nature | volume=208 | pages=575 | year=1965
| doi = 10.1016/j.asr.2005.05.071 }}</ref> Data from Mariner&nbsp;10 subsequently confirmed this view.<ref>{{cite web
| month=October | year=1976 | author=Davies, Merton E. et al
| url=http://history.nasa.gov/SP-423/mariner.htm
| title=Mariner&nbsp;10 Mission and Spacecraft
| work=SP-423 Atlas of Mercury
| publisher=NASA JPL | accessdate=2008-04-07 }}</ref> The 3:2 resonance results from Mercury's eccentric orbit, as the Sun raises higher tides on the planet at perihelion which, combined with the planet's high velocity then, make the planet spin faster. This also means that Schiaparelli's and Antoniadi's maps were not "wrong". Instead, the astronomers saw the same features during every ''second'' orbit and recorded them, but regarded those seen in the meantime, when Mercury's other face was toward the Sun, as spurious.

Ground-based observations did not shed much further light on the innermost planet, and it was not until space probes visited Mercury that many of its most fundamental properties became known. However, recent technological advances have led to improved ground-based observations. In 2000, high-resolution [[lucky imaging]] observations were conducted by the [[Mount Wilson Observatory]] 1.5 meter Hale telescope. They provided the first views that resolved some surface features on the parts of Mercury which were not imaged in the Mariner missions.<ref>{{cite journal
| last=Dantowitz | first=R. F. | coauthors=Teare, S. W.; Kozubal, M. J.
| title=Ground-based High-Resolution Imaging of Mercury
| journal=Astronomical Journal | volume=119 | pages=2455&ndash;2457 | year= 2000
| url=http://ukads.nottingham.ac.uk/cgi-bin/nph-bib_query?bibcode=2000AJ....119.2455D&amp;db_key=AST
| doi = 10.1016/j.asr.2005.05.071 }}</ref> Later imaging has shown evidence of a huge double-ringed impact basin even larger than the [[Caloris Basin]] in the non-Mariner-imaged hemisphere. It has informally been dubbed the ''[[Skinakas Basin]]''.<ref name=Ksa06>{{cite journal|author =Ksanfomality, L. V.|title= Earth-based optical imaging of Mercury | journal= Advances in Space Research |volume= 38|pages= 594|year= 2006|url= http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006AdSpR..38..594K&amp;db_key=AST&amp;data_type=HTML&amp;format=&amp;high=461152a03222956 | doi = 10.1016/j.asr.2005.05.071 <!--Retrieved from CrossRef by DOI bot-->}}</ref>
Most of the planet has been mapped by the Arecibo radar telescope, with 5&nbsp;km resolution, including polar deposits in shadowed craters of what may be water ice.<ref name=Harm06>{{cite journal|author =Harmon, J. K. et al|title= Mercury: Radar images of the equatorial and midlatitude zones| journal= Icarus |volume= 187|pages= 374|year= 2007|url= http://adsabs.harvard.edu/abs/2007Icar..187..374H | doi = 10.1016/j.icarus.2006.09.026 <!--Retrieved from CrossRef by DOI bot-->}}</ref>

[[Image:Mariner10.gif|thumb|The Mariner&nbsp;10 probe, the first probe to visit the innermost planet]]

===Research with space probes===
{{main|Exploration of Mercury}}

Reaching Mercury from Earth poses significant technical challenges, since the planet orbits so much closer to the Sun than does the Earth. A Mercury-bound [[spacecraft]] launched from Earth must travel over 91 million kilometers into the Sun’s [[gravity|gravitational]] [[potential well]]. Starting from the Earth’s [[orbital speed]] of 30&nbsp;km/s, the change in [[velocity]] ([[delta-v]]) the spacecraft must make to enter into a [[Hohmann transfer orbit]] that passes near Mercury is large compared to other planetary missions.<ref name="DunneCh4">{{cite book|title=The Voyage of Mariner&nbsp;10 — Mission to Venus and Mercury|author=Dunne, J. A. and Burgess, E.|chapterurl=http://history.nasa.gov/SP-424/ch4.htm|publisher=NASA History Office|year=1978|chapter=Chapter Four|url=http://history.nasa.gov/SP-424/|accessdate=2008-05-28}}</ref>

The [[potential energy]] liberated by moving down the Sun’s [[potential well]] becomes [[kinetic energy]]; requiring another large delta-v change to do anything other than rapidly pass by Mercury. In order to land safely or enter a stable orbit the spacecraft must rely entirely on rocket motors since [[aerobraking]] is ruled out because the planet has very little atmosphere. A trip to Mercury actually requires more rocket fuel than that required to [[escape velocity|escape]] the solar system completely. As a result, only two space probes have visited the planet so far.<ref name="JPLprofile1">{{cite web|url=http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mercury&Display=OverviewLong|title=Mercury|publisher=[[NASA]] Jet Propulsion Laboratory|date=[[May 5]], [[2008]] |accessdate=2008-05-29}}</ref> A proposed alternative approach would use a [[solar sail]] to attain a Mercury-synchronous orbit around the Sun.<ref>{{ cite journal
| last=Leipold | first=M.
| coauthors=Seboldt, W.; Lingner, S.; Borg, E.; Herrmann, A.; Pabsch, A.; Wagner, O.; Bruckner, J.
| title=Mercury sun-synchronous polar orbiter with a solar sail
| year=1996 | month=July | journal=Acta Astronautica
| volume=39 |issue=1 | pages = 143&ndash;151 | doi=10.1016/S0094-5765(96)00131-2 }}</ref>

====Mariner 10====
{{main|Mariner 10}}

[[Image:Mercury Mariner10.jpg|left|thumb|View of Mercury from Mariner&nbsp;10]]
The first spacecraft to visit Mercury was [[NASA]]’s [[Mariner 10|Mariner&nbsp;10]] (1974–75).<ref name="Dunne" /> The spacecraft used the gravity of [[Venus]] to adjust its orbital velocity so that it could approach Mercury, making it both the first spacecraft to use this [[Gravitational slingshot|gravitational “slingshot”]] effect and the first NASA mission to visit multiple planets.<ref name="DunneCh4" /> Mariner&nbsp;10 provided the first close-up images of Mercury’s surface, which immediately showed its heavily cratered nature, and also revealed many other types of geological features, such as the giant scarps which were later ascribed to the effect of the planet shrinking slightly as its iron core cools.<ref>{{cite web
| month=October | year=1976 | first=Tony | last=Phillips
| url=http://www.nasa.gov/vision/universe/solarsystem/20oct_transitofmercury.html
| title=NASA 2006 Transit of Mercury | work=SP-423 Atlas of Mercury
| publisher=NASA | accessdate=2008-04-07 }}</ref> Unfortunately, due to the length of Mariner&nbsp;10's orbital period, the same face of the planet was lit at each of Mariner&nbsp;10’s close approaches. This made observation of both sides of the planet impossible,<ref>{{cite web|url=http://sci.esa.int/science-e/www/category/index.cfm?fcategoryid=4586|title=BepiColumbo - Background Science|publisher=European Space Agency|accessdate=2008-05-30}}</ref> and resulted in the mapping of less than 45% of the planet’s surface.<ref name="USATMessenger">{{cite news|url=http://www.usatoday.com/tech/news/2004-08-16-mercury-may-shrink_x.htm|title=MESSENGER to test theory of shrinking Mercury|publisher=USA Today|author=Tariq Malik|date=[[August 16]], [[2004]] |accessdate=2008-05-23}}</ref>

On [[March 27]], [[1974]], two days before its first flyby of Mercury, Mariner 10's instruments began registering large amounts of unexpected ultraviolet radiation in the vicinity of Mercury. This led to the tentative identification of [[Mercury's moon]]. Shortly afterward, the source of some of the UV was identified as the star [[31 Crateris]], and Mercury's moon passed into astronomy's history books as a footnote.

The spacecraft made three close approaches to Mercury, the closest of which took it to within 327&nbsp;km of the surface.<ref name="AtlasM10">{{cite book|url=http://history.nasa.gov/SP-423/sp423.htm|title=Atlas of Mercury|publisher=[[NASA]] Office of Space Sciences|author=Merton E. Davies, et al|year=1978|chapter=Mariner&nbsp;10 Mission and Spacecraft|chapterurl=http://history.nasa.gov/SP-423/mariner.htm|accessdate=2008-05-30}}</ref> At the first close approach, instruments detected a magnetic field, to the great surprise of planetary geologists—Mercury’s rotation was expected to be much too slow to generate a significant [[dynamo]] effect. The second close approach was primarily used for imaging, but at the third approach, extensive magnetic data were obtained. The data revealed that the planet’s magnetic field is much like the Earth’s, which deflects the [[solar wind]] around the planet. However, the origin of Mercury’s magnetic field is still the subject of several competing theories.<ref name="Ness1">{{ cite journal | last = Ness| first = Norman F. | year = 1978| month = March|title=Mercury - Magnetic field and interior| journal = Space Science Reviews | volume = 21| pages = 527–553| bibcode = 1978SSRv...21..527N | url = http://adsabs.harvard.edu/full/1978SSRv...21..527N| accessdate = 2008-05-23|doi=10.1007/BF00240907}}</ref>

Just a few days after its final close approach, Mariner&nbsp;10 ran out of fuel. Since its orbit could no longer be accurately controlled, mission controllers instructed the probe to shut itself down on [[March 24]], 1975.<ref name="DunneCh8">{{cite book|title=The Voyage of Mariner&nbsp;10 — Mission to Venus and Mercury|author=Dunne, J. A. and Burgess, E.|chapterurl=http://history.nasa.gov/SP-424/ch8.htm|publisher=NASA History Office|year=1978|chapter=Chapter Eight|url=http://history.nasa.gov/SP-424/}}</ref> Mariner&nbsp;10 is thought to be still orbiting the Sun, passing close to Mercury every few months.<ref>{{cite web
| date=[[April 2]], [[2008]] | first=Ed | last=Grayzeck
| url=http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1973-085A
| title=Mariner&nbsp;10 | work=NSSDC Master Catalog
| publisher=NASA | accessdate=2008-04-07 }}</ref>

====MESSENGER====
{{main|MESSENGER}}
[[Image:MESSENGER Assembly.jpg|thumb|180px|MESSENGER being prepared for launch]]
A second NASA mission to Mercury, named MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging), was launched on [[August 3]] [[2004]], from the [[Cape Canaveral Air Force Station]] aboard a [[Boeing Delta 2]] rocket. It made a fly-by of the Earth in August 2005, and of Venus in October 2006 and June 2007 in order to place it onto the correct trajectory to reach an orbit around Mercury.<ref>{{cite web|year=2005|url = http://www.spaceref.com/news/viewsr.html?pid=18956| title = MESSENGER Engine Burn Puts Spacecraft on Track for Venus|publisher = SpaceRef.com | accessdate = 2006-03-02}}</ref> A first fly-by of Mercury occurred on January 14, 2008, and a second on October 6.<ref name="MessCountdown">{{cite web|url= http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=115|title= Countdown to MESSENGER's Closest Approach with Mercury|date= [[January 14]], [[2008]] | publisher= Johns Hopkins University Applied Physics Laboratory |accessdate= 2008-05-30}} </ref> A third is scheduled for September 29, 2009. Most of the hemisphere not imaged by Mariner&nbsp;10 has been or will be mapped during these fly-bys. The probe will then enter an elliptical orbit around the planet in March 2011; the nominal mapping mission is one terrestrial year.<ref name="MessCountdown" />

<!--[[Image:mercclose3.jpg|thumb|Mercury as imaged by the MESSENGER probe]]-->
The mission is designed to shed light on six key issues: Mercury’s high density, its geological history, the nature of its [[magnetic field]], the structure of its core, whether it really has ice at its poles, and where its tenuous atmosphere comes from. To this end, the probe is carrying imaging devices which will gather much higher resolution images of much more of the planet than Mariner&nbsp;10, assorted [[spectrometer]]s to determine abundances of elements in the crust, and [[magnetometer]]s and devices to measure velocities of charged particles. Detailed measurements of tiny changes in the probe’s velocity as it orbits will be used to infer details of the planet’s interior structure.<ref name="MSGRgrayzeck" />

====BepiColombo====
{{main|BepiColombo}}
The [[European Space Agency]] is planning a joint mission with [[Japan]] called [[BepiColombo]], which will orbit Mercury with two probes: one to map the planet and the other to study its [[magnetosphere]]<ref name="ESAColumboGoAhead">{{cite web|url=http://www.esa.int/esaSC/SEMC8XBE8YE_index_0.html|title=ESA gives go-ahead to build BepiColombo|date=[[February 26]], [[2007]]|publisher=[[European Space Agency]]|accessdate=2008-05-29}}</ref>. A [[Russia]]n [[Soyuz launch vehicle|Soyuz]] rocket will launch the bus carrying the two probes in 2013 from ESA's [[Guiana Space Center]] to take advantage of its equatorial location.<ref name="ESAColumboGoAhead" /> As with MESSENGER, the BepiColombo bus will make close approaches to other planets en route to Mercury for orbit-changing gravitational assists, passing the Moon and Venus and making several approaches to Mercury before entering orbit.<ref name="ESAColumboGoAhead" /> A combination of chemical and [[Ion thruster|ion engines]] will be used, the latter thrusting continuously for long intervals.<ref name="Bepitelegraph1">{{cite news|url=http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=&xml=/earth/2008/01/18/scimerc118.xml|title=Star Trek-style ion engine to fuel Mercury craft|author=Nic Fleming|publisher=The Telegraph|date=[[January 18]], [[2008]]|accessdate=2008-05-23}}</ref><ref name="ESAColumboGoAhead" /> The spacecraft bus will reach Mercury in 2019.<ref name="Bepitelegraph1" /> The bus will release the magnetometer probe into an elliptical orbit, then chemical rockets will fire to deposit the mapper probe into a circular orbit. Both probes will operate for a terrestrial year.<ref name="ESAColumboGoAhead" />

The mapper probe will carry an array of spectrometers similar to those on MESSENGER, and will study the planet at many different wavelengths including [[infrared]], [[ultraviolet]], [[X-ray]] and [[gamma ray]]. Apart from intensively studying the planet itself, mission planners also hope to use the probe's proximity to the Sun to test the predictions of [[General Relativity]] theory with improved accuracy.<ref>{{cite web|url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31350|title=Objectives|publisher=[[European Space Agency]]|date=[[February 21]], [[2006]]|accessdate=2008-05-29}}</ref>

The mission is named after [[Giuseppe Colombo|Giuseppe (Bepi) Colombo]], the scientist who first determined the nature of Mercury’s spin-orbit resonance and who was also involved in the planning of Mariner&nbsp;10’s gravity-assisted trajectory to the planet in 1974.<ref name="ESA pages" />

==Notes==
<div class="references-small">
<ol type="a">
<li>{{Note_label|A|a|none}}1/30 of a degree is the fractional equivalent to 2.1 arcminutes.</li>
<li>{{Note_label|B|b|none}}Some sources precede the cuniform transcription with "MUL". "MUL" is a cuneiform sign that was used in the Sumerian language to designate a star or planet, but it is not considered part of the actual name. The "4" is a reference number in the Sumero-Akkadian transliteration system to designate which of several syllables a certain cuneiform sign is most likely designating.</li>
</ol>
</div>


==References==
==References==
{{reflist|2}}
{{reflist}}

==External links==
{{SpecialChars}}
{{Spoken Wikipedia|En-Mercury(Planet).ogg|2008-01-16}}
{{sisterlinks|Mercury}}
* [http://space.about.com/cs/solarsystem/p/mercuryinfo.htm Mercury] — About Space
* [http://history.nasa.gov/SP-423/sp423.htm Atlas of Mercury — NASA]
* [http://www.nineplanets.org/mercury.html Nine Planets Information]
* [http://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html NASA’s Mercury fact sheet]
* [http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mercury Mercury Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.esa.int/export/esaSC/120391_index_0_m.html ‘BepiColombo’, ESA’s Mercury Mission]
* [http://www.flug-ins-all.de/planeten/der-merkur Merkur(dt.)]
* [http://messenger.jhuapl.edu/ ‘Messenger’, NASA’s Mercury Mission]
* [http://www.solarviews.com/eng/mercury.htm SolarViews.com — Mercury]
* [http://www.projectshum.org/Planets/mercury.html Planets — Mercury] A kid’s guide to Mercury.
* [http://www.nasa.gov/worldbook/mercury_worldbook.html Mercury ''World Book Online Reference Center'']
* [http://www.astronomycast.com/astronomy/episode-49-mercury/ Astronomy Cast: Mercury]
* [http://www.geody.com/?world=mercury Geody Mercury] World’s search engine that supports [[NASA World Wind]], [[Celestia]], and other applications.
* [http://btc.montana.edu/MESSENGER/Interactives/ANIMATIONS/Day_On_Mercury/day_on_mercury_full.htm A Day On Mercury] flash animation
* [http://www.psrd.hawaii.edu/Archive/Archive-Mercury.html Mercury articles in Planetary Science Research Discoveries]

{{portal|Solar System|Solar system.jpg}}
{{Solar System}}
{{Mercury (planet)}}

[[Category:Mercury| ]]
[[Category:Terrestrial planets]]


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[[ar:عطارد]]
[[an:Mercurio (planeta)]]
[[frp:Mèrcure (planèta)]]
[[ast:Mercuriu (planeta)]]
[[az:Merkuri (planet)]]
[[bn:বুধ গ্রহ]]
[[zh-min-nan:Chúi-chheⁿ]]
[[map-bms:Merkurius]]
[[be:Планета Меркурый]]
[[be-x-old:Мэркурый (плянэта)]]
[[bs:Merkur]]
[[br:Merc'her (planedenn)]]
[[bg:Меркурий (планета)]]
[[ca:Mercuri (planeta)]]
[[ceb:Mercury (planeta)]]
[[cs:Merkur (planeta)]]
[[cy:Mercher (planed)]]
[[da:Merkur (planet)]]
[[de:Merkur (Planet)]]
[[et:Merkuur]]
[[el:Ερμής (πλανήτης)]]
[[es:Mercurio (planeta)]]
[[eo:Merkuro]]
[[eu:Merkurio (planeta)]]
[[fa:تیر (سیاره)]]
[[fo:Merkur]]
[[fr:Mercure (planète)]]
[[ga:Mearcair (pláinéad)]]
[[gv:Crean (planaid)]]
[[gd:Mearcair]]
[[gl:Mercurio (planeta)]]
[[gan:水星]]
[[gu:બુધ (ગ્રહ)]]
[[zh-classical:水星]]
[[ko:수성]]
[[haw:Ukaliali‘i]]
[[hy:Մերկուրի]]
[[hi:बुध]]
[[hsb:Merkur (planet)]]
[[hr:Merkur (planet)]]
[[io:Merkuro]]
[[ilo:Mercurio (planeta)]]
[[id:Merkurius]]
[[ia:Mercurio (planeta)]]
[[os:Меркурий (планетæ)]]
[[is:Merkúríus (reikistjarna)]]
[[it:Mercurio (astronomia)]]
[[he:כוכב חמה]]
[[jv:Merkurius]]
[[pam:Mercury]]
[[kn:ಬುಧ]]
[[ka:მერკური (პლანეტა)]]
[[csb:Merkùri]]
[[kk:Болпан]]
[[kw:Mergher (planet)]]
[[sw:Utaridi]]
[[ht:Mèki (planèt)]]
[[ku:Tîr (gerstêrk)]]
[[la:Mercurius (planeta)]]
[[lv:Merkurs (planēta)]]
[[lb:Merkur (Planéit)]]
[[lt:Merkurijus (planeta)]]
[[lij:Mercurio (astronomia)]]
[[li:Mercurius (planeet)]]
[[hu:Merkúr]]
[[mk:Меркур]]
[[ml:ബുധന്‍ (ഗ്രഹം)]]
[[mt:Merkurju (pjaneta)]]
[[mr:बुध ग्रह]]
[[ms:Utarid]]
[[mn:Буд]]
[[my:ဗုဒ္ဓဟူးဂြိုဟ်]]
[[nah:Payīnalcītlalli]]
[[nl:Mercurius (planeet)]]
[[nds-nl:Merkurius (planeet)]]
[[ne:बुधग्रह]]
[[ja:水星]]
[[no:Merkur]]
[[nn:Planeten Merkur]]
[[nrm:Mèrtchure]]
[[nov:Merkurie (planete)]]
[[oc:Mercuri (planeta)]]
[[pl:Merkury]]
[[pt:Mercúrio (planeta)]]
[[ksh:Merrkuur (Planneet)]]
[[ro:Mercur (planetă)]]
[[rm:Mercur (planet)]]
[[qu:Qatuylla]]
[[ru:Меркурий (планета)]]
[[se:Merkurius]]
[[sq:Mërkuri]]
[[scn:Mircuriu (pianeta)]]
[[simple:Mercury (planet)]]
[[sk:Merkúr]]
[[sl:Merkur]]
[[sr:Меркур (планета)]]
[[sh:Merkur]]
[[fi:Merkurius]]
[[sv:Merkurius]]
[[tl:Merkuryo (planeta)]]
[[ta:புதன் (கோள்)]]
[[te:బుధుడు]]
[[th:ดาวพุธ]]
[[vi:Sao Thủy]]
[[tg:Уторид]]
[[tr:Merkür (gezegen)]]
[[uk:Меркурій (планета)]]
[[ur:عطارد]]
[[vec:Mercùrio (pianeta)]]
[[yi:מערקור]]
[[zh-yue:水星]]
[[bat-smg:Merkorėjos (planeta)]]
[[zh:水星]]

Revision as of 22:13, 10 October 2008

Template:Future album

Untitled

Night Electric Night is the third studio album by Swedish industrial metal band Deathstars. It is scheduled for release in January 2009 by Nuclear Blast. The album was initially recorded under the working title Deathglam.

Album title

Production of the third album by Deathstars was revealed in an interview with the band conducted by Anthony Morgan of Lucem Fero in early 2008, where it was referred to by its working title, Deathglam.[1] Vocalist Whiplasher Bernadotte expanded on the title, saying, ". . . it'll just continue with the deathglam that we play. In terms of this new album's style, I think it's more Deathstars than ever . . ."

Recently, the band has announced on their official website that the record has been re-dubbed Night Electric Night.

Metallica controversy

Deathstars have recently made claim that that they were an inspiration on American thrash metal band Metallica's use of Deathstars' logotype font on the packaging of their 2008 album Death Magnetic, and a song titled "Cyanide" appearing on the album (a song of the same name by Deathstars appeared on 2006's Termination Bliss). In regards to this, an update on Deathstars' website ended with a joke that their third studio album would be titled Master of Muppets, and would be available for free download on January 30, 2009. This title is a reference to Metallica's 1986 album Master of Puppets.

Metallica have not responded to the claims posed by Deathstars, though it is likely the latter band does not take the "inspiration" they had seriously, as Whiplasher Bernadotte clarified, "It's just fun. What can I say, it's just as big of a coincidence and chance as if you get a hermaphrodite-child. What can you do..? You just need to smile at the little monster."

Track listing

Confirmed working titles

  • "Blood Stains Blondes"
  • "Chertograd"
  • "Night Electric Night"
  • "Opium"
  • "Venus in Arms"

Personnel

References

  1. ^ [1]
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