Miranda (moon)

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Miranda (disambiguation).
Miranda
Miranda
Discovery
Discovered by Gerard P. Kuiper
Discovery date February 16, 1948
Designations
Pronunciation /mɨˈrændə/ mi-RAN-də
Uranus V
Adjectives Mirandan, Mirandian
Orbital characteristics
129390 km
Eccentricity 0.0013
1.413479 d
6.66 km/s (calculated)
Inclination 4.232° (to Uranus's equator)
Satellite of Uranus
Physical characteristics
Dimensions 480 × 468.4 × 465.8 km
Mean radius
235.8±0.7 km (0.03697 Earths)[1]
700000 km2
Volume 54835000 km3
Mass

(6.59±0.75)×1019 kg[2]

(1.103×10−5 Earths)
Mean density
1.20±0.15 g/cm3[2]
0.079 m/s2
0.193 km/s
synchronous
Albedo 0.32
Surface temp. min mean max
solstice[4] ? ≈ 60 K 84±1 K
15.8[3]

Miranda is the smallest and innermost of Uranus's five major moons.

It was discovered by Gerard Kuiper on February 16, 1948 at McDonald Observatory. It was named after Miranda from William Shakespeare's play The Tempest by Kuiper in his report of the discovery.[5] The adjectival form of the name is Mirandan. It is also designated Uranus V.

So far the only close-up images of Miranda are from the Voyager 2 probe, which made observations of the moon during its Uranus flyby in January 1986. During the flyby the southern hemisphere of the moon was pointed towards the Sun so only that part was studied. Miranda shows more evidence of past geologic activity than any of the other Uranian satellites.

Physical characteristics[edit]

Close-up view of Verona Rupes, a large fault scarp on Miranda, possibly 5 km (3.1 mi) high[6][7]

Miranda's surface may be mostly water ice, with the low-density body also probably containing silicate rock and organic compounds in its interior.

Miranda's surface has patchwork regions of broken terrain indicating intense geological activity in the moon's past, and is criss-crossed by huge canyons. Large 'racetrack'-like grooved structures, called coronae, may have formed via extensional processes at the tops of diapirs, or upwellings of warm ice.[7][8] The ridges probably represent extensional tilt blocks. The canyons probably represent graben formed by extensional faulting. Other features may be due to cryovolcanic eruptions of icy magma. The diapirs may have changed the density distribution within the moon, which could have caused Miranda to reorient itself,[9] similar to a process believed to have occurred at Saturn's geologically active moon Enceladus.

Miranda's past geological activity is believed to have been driven by tidal heating at a time when its orbit was more eccentric than currently. Early in its history, Miranda was apparently captured into a 3:1 orbital resonance with Umbriel, from which it subsequently escaped.[10] The resonance would have increased orbital eccentricity; resulting tidal friction due to time-varying tidal forces from Uranus would have caused warming of the moon's interior. In the Uranian system, due to the planet's lesser degree of oblateness, and the larger relative size of its satellites, escape from a mean motion resonance is much easier than for satellites of Jupiter or Saturn. Miranda's orbital inclination (4.34°) is unusually high for a body so close to the planet. Miranda probably escaped from its resonance with Umbriel via a secondary resonance, and the mechanism of this escape is believed to explain why its orbital inclination is more than 10 times those of the other large Uranian moons (see moons of Uranus).[11][12]

Miranda may have also once been in a 5:3 resonance with Ariel, which would have also contributed to its internal heating. However, the maximum heating attributable to the resonance with Umbriel was likely about three times greater.[10]

An earlier theory, proposed shortly after the Voyager 2 flyby, was that a previous incarnation of Miranda was shattered by a massive impact, with the fragments reassembling and denser ones subsequently sinking to produce the current strange pattern.[7]

Approaching the 7 December 2007 equinox Miranda produced brief solar eclipses over the center of Uranus.

Scientists recognize the following geological features on Miranda:

See also[edit]

References[edit]

  1. ^ Thomas, P. C. (1988). "Radii, shapes, and topography of the satellites of Uranus from limb coordinates". Icarus 73 (3): 427–441. Bibcode:1988Icar...73..427T. doi:10.1016/0019-1035(88)90054-1.  edit
  2. ^ a b Jacobson, R. A.; Campbell, J. K.; Taylor, A. H.; Synnott, S. P. (June 1992). "The masses of Uranus and its major satellites from Voyager tracking data and earth-based Uranian satellite data". The Astronomical Journal 103 (6): 2068–2078. Bibcode:1992AJ....103.2068J. doi:10.1086/116211.  edit
  3. ^ "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2009-04-03. Retrieved 2009-08-10. 
  4. ^ Hanel, R.; Conrath, B.; Flasar, F. M.; Kunde, V.; Maguire, W.; Pearl, J.; Pirraglia, J.; Samuelson, R.; Cruikshank, D. (4 July 1986). "Infrared Observations of the Uranian System". Science 233 (4759): 70–74. Bibcode:1986Sci...233...70H. doi:10.1126/science.233.4759.70. PMID 17812891.  edit
  5. ^ Kuiper, G. P., The Fifth Satellite of Uranus, Publications of the Astronomical Society of the Pacific, Vol. 61, No. 360, p. 129, June 1949
  6. ^ "PIA00044: Miranda high resolution of large fault". JPL, NASA. Retrieved 2007-07-23. 
  7. ^ a b c Chaikin, Andrew (2001-10-16). "Birth of Uranus' Provocative Moon Still Puzzles Scientists". Space.com. Imaginova Corp. Retrieved 2007-12-07. [dead link]
  8. ^ Pappalardo, Robert T.; Reynolds, Stephen J.; Greeley, Ronald (1997-06-25). "Extensional tilt blocks on Miranda: Evidence for an upwelling origin of Arden Corona". Journal of Geophysical Research 102 (E6): 13,369–13,380. Bibcode:1997JGR...10213369P. doi:10.1029/97JE00802.  edit
  9. ^ Pappalardo, Robert T.; Greeley, Ronald (1993). "Structural evidence for reorientation of Miranda about a paleo-pole". In Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z. pp. 1111–1112. Retrieved 2006-08-05. 
  10. ^ a b Tittemore, William C.; Wisdom, Jack (June 1990). "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. Bibcode:1990Icar...85..394T. doi:10.1016/0019-1035(90)90125-S.  edit
  11. ^ Tittemore, William C.; Wisdom, Jack (March 1989). "Tidal evolution of the Uranian satellites: II. An explanation of the anomalously high orbital inclination of Miranda". Icarus 78 (1): 63–89. Bibcode:1989Icar...78...63T. doi:10.1016/0019-1035(89)90070-5.  edit
  12. ^ Malhotra, Renu; Dermott, Stanley F. (June 1990). "The role of secondary resonances in the orbital history of Miranda". Icarus 85 (2): 444–480. Bibcode:1990Icar...85..444M. doi:10.1016/0019-1035(90)90126-T. ISSN 0019-1035.  edit

External links[edit]