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{{Infobox Planet|image=MirandaVoyagerColor.jpg
|caption=True-color composite image of Miranda by [[Voyager 2]]
|order=14
|date=February 16, 1948<ref name=usgs>"[http://planetarynames.wr.usgs.gov/append7.html Gazetteer of Planetary Nomenclature: Planetary Body Names and Discoverers]." US Geological Survey, Jennifer Blue, ed. March 31, 2008. Accessed April 17, 2008.</ref>
|discname=Gerard P. Kuiper<ref name=usgs/><ref name=Hamilton>Hamilton, Calvin J. "[http://www.solarviews.com/eng/miranda.htm Entry for 'Miranda, A Moon of Uranus']." ''Views of the Solar System'', 2007. Accessed April 28, 2008.</ref><ref name=Kuiper>Kuiper, Gerard P. "[http://adsabs.harvard.edu//full/seri/PASP./0061//0000129.000.html The Fifth Satellite of Uranus]." Publications of the Astronomical Society of the Pacific, 61(360):129, June 1946. Accessed April 28, 2008.</ref>
|origname=Female lead in William Shakespeare's play ''The Tempest''<ref name=usgs/><ref name=Kuiper/>
|primary=Uranus
|periapsis=129,450 km<ref name=calc>Calculated</ref>
|apoapsis=130,150 km<ref name=calc/>
|semimajor=129,800 km<ref name=ssdhoriz>"[http://ssd.jpl.nasa.gov/horizons.cgi HORIZONS on Miranda]." ''Solar System Dynamics'', Jet Propulsion Laboratory, NASA, August 2, 2007. Accessed April 28, 2008.</ref>
|eccentricity=0.0027<ref name=ssdhoriz/>
|sidereal=1.413 da<ref name=ssdhoriz/>
|inclination=4.22°<ref name=ssdhoriz/>
|siderealday=1.413 da<ref name=ssdhoriz/>
|rotatespeed=1.021 m/s<ref name=calc/>
|axialtilt=0°
|mass=6.59 * 10<sup>19</sup> kg (0.09% [[Moon]])<ref name=ssdhoriz/>
|density=1,200 kg/m³<ref name=ssdhoriz/>
|surfacegrav=0.0802 m/s²
|escapespeed=0.194 km/s
|meanradius=234.2 km<ref name=ssdhoriz/>
|equatorradius=240 km<ref name=ssdhoriz/>
|polarradius=232.9 km<ref name=ssdhoriz/>
|surfacearea=689,261 km²<ref name=calc/>
|maxtemp=86 K<ref name=Hamilton/>
|composition=Ice and rock
|color=Light purple-gray
|albedo=0.27<ref name=ssdhoriz/>
}}'''Miranda''' or '''Uranus V''' is the fourteenth [[moon]] of [[Uranus]] in orbital order, and easily the most remarkable. It is also the fifth satellite to be discovered.
== Discovery ==
Gerard P. Kuiper discovered miranda in 1948. He rejected at once naming the satellite after a son of Uranus, because earlier astronomers had already used Uranus' sons as names for [[Saturn]]'s moons. He therefore followed the lead of Lassel and Herschel<ref name=usgs/> and named Miranda after a character in one of the plays of William Shakespeare.<ref name=Kuiper/>
When [[Voyager 2]] flew by Uranus in 1986, Miranda was the closest moon to Voyager's flight path, and was therefore the one that Voyager 2 studied most closely. The Voyager team originally had not planned a mission to so small a moon, but could do nothing else; Voyager needed to make a precise hyperbolic pass at Uranus in order to steer toward [[Neptune]], and Miranda happened to lie along the way. Yet in the end the Voyager scientists were grateful for the opportunity to study this remarkable object.<ref name=nasa1>Harvey, Samantha. "[http://solarsystem.nasa.gov/planets/profile.cfm?Object=Ura_Miranda Uranus: Moons: Miranda]." ''Our Solar System'', [[NASA]], February 23, 2007. Accessed April 28, 2008.</ref><ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/miranda.html Miranda]." ''The <s>Nine</s> 8 Planets'', December 15, 2004. Accessed April 28, 2008.</ref>
== Orbital characteristics ==
Miranda's orbit is one of the least eccentric of those of the five "major moons" of Uranus. While some of Uranus' moons have orbits that are less eccentric by an order of magnitude, [[Umbriel]]'s orbit is significantly more eccentric than that of Miranda, and many of the other satellites have orbits more eccentric still.
More significantly, Miranda's orbit is inclined with respect to Uranus' equator by more than four degrees. This is the highest inclination among the orbits of the "major moons," although some of Uranus' moons have orbits that are inclined by more than forty-five degrees.
== Rotational characteristics ==
Miranda orbits Uranus once every 33 hours, and is tidally locked to Uranus. This [[tidal locking]] does not allow Miranda to have a significant axial tilt.
== Physical characteristics ==
Miranda's mass is less than 0.09% of the mass of [[Earth]]'s [[Moon]]. At only 1200 kilograms per cubic meter, it is also one of the least dense, less dense even than the [[sun]]. Its density is closest to that of water, and so Miranda is believed to be composed mainly of ice with some rock.
Miranda has the most striking landscape of any spheroidal celestial body other than the earth. Its largest surface features are extremely striking in their bizarre variety and stark relief, almost as if Miranda were an object that someone pieced together out of scrap metal.<ref name=planetsoc>"[http://www.planetary.org/explore/topics/uranus/miranda.html Uranus' Moon Miranda]." The Planetary Society. Accessed April 28, 2008.</ref> Twenty-kilometer canyons<ref name=nasa1/><ref name=Arnett/> give way to cratered regions<ref name=planetsoc/> and other regions nearly devoid of craters. The mixture of geologically "old" and "young" regions is quite puzzling.<ref name=nasa1/>
==Gallery==
<gallery>
Image:Miranda.jpg|South pole region showing some of Miranda's most striking features
Image:MirandaFault.jpg|High-resolution image of a fault line
</gallery>
==Difficulties for uniformitarian theories==
The geological activity required to produce Miranda's striking mix of surface features defies explanation.<ref name=Chaikin>Chaikin, Andrew. "[http://www.space.com/scienceastronomy/solarsystem/miranda_creation_011016-1.html Birth of Uranus' Provocative Moon Still Puzzles Scientists]." <http://www.space.com/> October 16, 2001. Accessed April 28, 2008.</ref>
Shortly after the Voyager 2 flyby, [[Astronomy|astronomers]] proposed that Miranda was shattered five times by collisions and then reassembled by mutual gravitational attraction.<ref name=Chaikin/><ref name=Arnett/><ref name=planetsoc/><ref name=nasa1/> But such a small moon would not be likely to survive even one collision, much less five. This theory is now out of favor.
The current favored theory is that Miranda was once in a 1:3 orbital resonance with [[Umbriel]], and then escaped that resonance. While Miranda was resonating with Umbriel, its orbit gained in eccentricity and thus subjected it to [[tidal heating]]. To support that theory, astronomers point out that Miranda's orbit, inclined 4.22° from Uranus' equator, is more severely inclined than that of any other satellite in the Uranian system.<ref>Tittemore, William C., and Wisdom, Jack. "Tidal evolution of the Uranian satellites II. An explanation of the anomalously high orbital inclination of Miranda." ''Icarus'' 78(1):63-89, March 1989. Accessed April 28, 2008. <doi:10.1016/0019-1035(89)90070-5></ref><ref>Tittemore, William C., and Wisdom, Jack. "Tidal evolution of the Uranian satellites III. Evolution through the Miranda-Umbriel 3:1, Miranda-Ariel 5:3, and Ariel-Umbriel 2:1 mean-motion commensurabilities." ''Icarus'' 85(2):394-443, June 1990. Accessed April 28, 2003. <doi:10.1016/0019-1035(90)90125-S></ref><ref>Malhotra, Renu, and Dermott, Stanley F. "The role of secondary resonances in the orbital history of Miranda." ''Icarus'' 85(2):444-480, June 1990. <doi:10.1016/0019-1035(90)90126-T></ref>
But this begs the question of how orbital resonances form, or how a satellite, once in such a resonance, would escape it. More to the point, however, is that the orbit of Miranda is not the most strikingly eccentric orbit in the Uranian system. Even among the major moons, that distinction belongs to Umbriel, not Miranda.
Still other geologists insist that upwelling of subsurface ice can explain all of Miranda's features without the need to invoke cataclysmic shattering and re-formation.<ref>Pappalardo, R. T., S. J. Reynolds, and R. Greeley (1997), [http://www.agu.org/pubs/crossref/1997/97JE00802.shtml Extensional tilt blocks on Miranda: Evidence for an upwelling origin of Arden Corona], ''J. Geophys. Res''., 102(E6), 13,369–13,379.</ref>
== References ==
{{reflist|2}}
{{solarsystem}}
|caption=True-color composite image of Miranda by [[Voyager 2]]
|order=14
|date=February 16, 1948<ref name=usgs>"[http://planetarynames.wr.usgs.gov/append7.html Gazetteer of Planetary Nomenclature: Planetary Body Names and Discoverers]." US Geological Survey, Jennifer Blue, ed. March 31, 2008. Accessed April 17, 2008.</ref>
|discname=Gerard P. Kuiper<ref name=usgs/><ref name=Hamilton>Hamilton, Calvin J. "[http://www.solarviews.com/eng/miranda.htm Entry for 'Miranda, A Moon of Uranus']." ''Views of the Solar System'', 2007. Accessed April 28, 2008.</ref><ref name=Kuiper>Kuiper, Gerard P. "[http://adsabs.harvard.edu//full/seri/PASP./0061//0000129.000.html The Fifth Satellite of Uranus]." Publications of the Astronomical Society of the Pacific, 61(360):129, June 1946. Accessed April 28, 2008.</ref>
|origname=Female lead in William Shakespeare's play ''The Tempest''<ref name=usgs/><ref name=Kuiper/>
|primary=Uranus
|periapsis=129,450 km<ref name=calc>Calculated</ref>
|apoapsis=130,150 km<ref name=calc/>
|semimajor=129,800 km<ref name=ssdhoriz>"[http://ssd.jpl.nasa.gov/horizons.cgi HORIZONS on Miranda]." ''Solar System Dynamics'', Jet Propulsion Laboratory, NASA, August 2, 2007. Accessed April 28, 2008.</ref>
|eccentricity=0.0027<ref name=ssdhoriz/>
|sidereal=1.413 da<ref name=ssdhoriz/>
|inclination=4.22°<ref name=ssdhoriz/>
|siderealday=1.413 da<ref name=ssdhoriz/>
|rotatespeed=1.021 m/s<ref name=calc/>
|axialtilt=0°
|mass=6.59 * 10<sup>19</sup> kg (0.09% [[Moon]])<ref name=ssdhoriz/>
|density=1,200 kg/m³<ref name=ssdhoriz/>
|surfacegrav=0.0802 m/s²
|escapespeed=0.194 km/s
|meanradius=234.2 km<ref name=ssdhoriz/>
|equatorradius=240 km<ref name=ssdhoriz/>
|polarradius=232.9 km<ref name=ssdhoriz/>
|surfacearea=689,261 km²<ref name=calc/>
|maxtemp=86 K<ref name=Hamilton/>
|composition=Ice and rock
|color=Light purple-gray
|albedo=0.27<ref name=ssdhoriz/>
}}'''Miranda''' or '''Uranus V''' is the fourteenth [[moon]] of [[Uranus]] in orbital order, and easily the most remarkable. It is also the fifth satellite to be discovered.
== Discovery ==
Gerard P. Kuiper discovered miranda in 1948. He rejected at once naming the satellite after a son of Uranus, because earlier astronomers had already used Uranus' sons as names for [[Saturn]]'s moons. He therefore followed the lead of Lassel and Herschel<ref name=usgs/> and named Miranda after a character in one of the plays of William Shakespeare.<ref name=Kuiper/>
When [[Voyager 2]] flew by Uranus in 1986, Miranda was the closest moon to Voyager's flight path, and was therefore the one that Voyager 2 studied most closely. The Voyager team originally had not planned a mission to so small a moon, but could do nothing else; Voyager needed to make a precise hyperbolic pass at Uranus in order to steer toward [[Neptune]], and Miranda happened to lie along the way. Yet in the end the Voyager scientists were grateful for the opportunity to study this remarkable object.<ref name=nasa1>Harvey, Samantha. "[http://solarsystem.nasa.gov/planets/profile.cfm?Object=Ura_Miranda Uranus: Moons: Miranda]." ''Our Solar System'', [[NASA]], February 23, 2007. Accessed April 28, 2008.</ref><ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/miranda.html Miranda]." ''The <s>Nine</s> 8 Planets'', December 15, 2004. Accessed April 28, 2008.</ref>
== Orbital characteristics ==
Miranda's orbit is one of the least eccentric of those of the five "major moons" of Uranus. While some of Uranus' moons have orbits that are less eccentric by an order of magnitude, [[Umbriel]]'s orbit is significantly more eccentric than that of Miranda, and many of the other satellites have orbits more eccentric still.
More significantly, Miranda's orbit is inclined with respect to Uranus' equator by more than four degrees. This is the highest inclination among the orbits of the "major moons," although some of Uranus' moons have orbits that are inclined by more than forty-five degrees.
== Rotational characteristics ==
Miranda orbits Uranus once every 33 hours, and is tidally locked to Uranus. This [[tidal locking]] does not allow Miranda to have a significant axial tilt.
== Physical characteristics ==
Miranda's mass is less than 0.09% of the mass of [[Earth]]'s [[Moon]]. At only 1200 kilograms per cubic meter, it is also one of the least dense, less dense even than the [[sun]]. Its density is closest to that of water, and so Miranda is believed to be composed mainly of ice with some rock.
Miranda has the most striking landscape of any spheroidal celestial body other than the earth. Its largest surface features are extremely striking in their bizarre variety and stark relief, almost as if Miranda were an object that someone pieced together out of scrap metal.<ref name=planetsoc>"[http://www.planetary.org/explore/topics/uranus/miranda.html Uranus' Moon Miranda]." The Planetary Society. Accessed April 28, 2008.</ref> Twenty-kilometer canyons<ref name=nasa1/><ref name=Arnett/> give way to cratered regions<ref name=planetsoc/> and other regions nearly devoid of craters. The mixture of geologically "old" and "young" regions is quite puzzling.<ref name=nasa1/>
==Gallery==
<gallery>
Image:Miranda.jpg|South pole region showing some of Miranda's most striking features
Image:MirandaFault.jpg|High-resolution image of a fault line
</gallery>
==Difficulties for uniformitarian theories==
The geological activity required to produce Miranda's striking mix of surface features defies explanation.<ref name=Chaikin>Chaikin, Andrew. "[http://www.space.com/scienceastronomy/solarsystem/miranda_creation_011016-1.html Birth of Uranus' Provocative Moon Still Puzzles Scientists]." <http://www.space.com/> October 16, 2001. Accessed April 28, 2008.</ref>
Shortly after the Voyager 2 flyby, [[Astronomy|astronomers]] proposed that Miranda was shattered five times by collisions and then reassembled by mutual gravitational attraction.<ref name=Chaikin/><ref name=Arnett/><ref name=planetsoc/><ref name=nasa1/> But such a small moon would not be likely to survive even one collision, much less five. This theory is now out of favor.
The current favored theory is that Miranda was once in a 1:3 orbital resonance with [[Umbriel]], and then escaped that resonance. While Miranda was resonating with Umbriel, its orbit gained in eccentricity and thus subjected it to [[tidal heating]]. To support that theory, astronomers point out that Miranda's orbit, inclined 4.22° from Uranus' equator, is more severely inclined than that of any other satellite in the Uranian system.<ref>Tittemore, William C., and Wisdom, Jack. "Tidal evolution of the Uranian satellites II. An explanation of the anomalously high orbital inclination of Miranda." ''Icarus'' 78(1):63-89, March 1989. Accessed April 28, 2008. <doi:10.1016/0019-1035(89)90070-5></ref><ref>Tittemore, William C., and Wisdom, Jack. "Tidal evolution of the Uranian satellites III. Evolution through the Miranda-Umbriel 3:1, Miranda-Ariel 5:3, and Ariel-Umbriel 2:1 mean-motion commensurabilities." ''Icarus'' 85(2):394-443, June 1990. Accessed April 28, 2003. <doi:10.1016/0019-1035(90)90125-S></ref><ref>Malhotra, Renu, and Dermott, Stanley F. "The role of secondary resonances in the orbital history of Miranda." ''Icarus'' 85(2):444-480, June 1990. <doi:10.1016/0019-1035(90)90126-T></ref>
But this begs the question of how orbital resonances form, or how a satellite, once in such a resonance, would escape it. More to the point, however, is that the orbit of Miranda is not the most strikingly eccentric orbit in the Uranian system. Even among the major moons, that distinction belongs to Umbriel, not Miranda.
Still other geologists insist that upwelling of subsurface ice can explain all of Miranda's features without the need to invoke cataclysmic shattering and re-formation.<ref>Pappalardo, R. T., S. J. Reynolds, and R. Greeley (1997), [http://www.agu.org/pubs/crossref/1997/97JE00802.shtml Extensional tilt blocks on Miranda: Evidence for an upwelling origin of Arden Corona], ''J. Geophys. Res''., 102(E6), 13,369–13,379.</ref>
== References ==
{{reflist|2}}
{{solarsystem}}