Europa (moon)

Europa
Europa, as imaged by the Juno spacecraft, September 2022.[1] Numerous dark lineae criss-cross its geologically young surface.
Discovery
Discovered byGalileo Galilei
Simon Marius
Discovery date8 January 1610[2]
Designations
Pronunciation/jʊˈroʊpə/[3]
Named after
Ευρώπη Eurōpē
Alternative names
Jupiter II
AdjectivesEuropan /jʊˈroʊpən/[4][5]
Orbital characteristics[6]
Epoch 8 January 2004
Periapsis664862 km[a]
Apoapsis676938 km[b]
Mean orbit radius
670900 km[7]
Eccentricity0.009[7]
3.551181 d[7]
Average orbital speed
13743.36 m/s[8]
Inclination0.470° (to Jupiter's equator)
1.791° (to the ecliptic)[7]
Satellite ofJupiter
GroupGalilean moon
Physical characteristics
Mean radius
1560.8±0.5 km
(0.245 Earths)[9]
3.061×107 km2
(0.061 Earths)[c]
Volume1.593×1010 km3
(0.015 Earths)[d]
Mass4.79984×1022 kg
(0.008 Earths)[9]
Mean density
3.013±0.005 g/cm3
(0.546 Earths)[9]
Surface gravity
1.314 m/s2
(0.134 g)[e]
Moment of inertia factor
0.346±0.005[10] (estimate)
2.025 km/s[f]
Synodic rotation period
Synchronous[11]
0.1°[12] (to Jupiter)
North pole right ascension
268.08° [13]
North pole declination
64.51° [13]
Albedo0.67 ± 0.03[9]
Surface temp. min mean max
Surface ≈ 50 K[14] 102 K (−171 °C) 125 K
5.29 (opposition)[9]
Atmosphere
Surface pressure
0.1 μPa (10−12 bar)[15]

Europa (/jʊˈroʊpə/ ⓘ) is the smallest and least massive of the four Galilean moons of Jupiter. It is observable from Earth with common binoculars and is a planetary-mass moon, slightly smaller and less massive than Earth's Moon. Europa is an icy moon, and, of the three icy Galilean moons, the closest orbiting Jupiter. As a result, it exhibits a relatively young surface, driven by tidal heating.

Probably having an iron–nickel core, it consists mainly of silicate rock, with a water-ice shell.[16] It has a very thin atmosphere, composed primarily of oxygen. Its geologically young white-beige surface is striated by light tan cracks and streaks, with very few impact craters. In addition to Earth-bound telescope observations, Europa has been examined by a succession of space-probe flybys, the first occurring in the early 1970s. In September 2022, the Juno spacecraft flew within about 320 km (200 miles) of Europa for a more recent close-up view.[17]

Europa has the smoothest surface of any known solid object in the Solar System. The apparent youth and smoothness of the surface is due to a water ocean beneath the surface, which could conceivably harbor extraterrestrial life.[18] The predominant model suggests that heat from tidal flexing causes the ocean to remain liquid and drives ice movement similar to plate tectonics, absorbing chemicals from the surface into the ocean below.[19][20] Sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the sea floor. This may be important in determining whether Europa could be habitable.[21] In addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturn's moon Enceladus, which are thought to be caused by erupting cryogeysers.[22] In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated analysis of data obtained from the Galileo space probe, which orbited Jupiter from 1995 to 2003. Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon.[23][24][25][26] In March 2024, astronomers reported that the surface of Europa may have much less oxygen than previously inferred.[27][28]

Europa was discovered independently by Simon Marius and Galileo Galilei.[2] Marius later named it after Europa, the Phoenician mother of King Minos of Crete and lover of Zeus, the Greek equivalent of the Roman god Jupiter. The Galileo mission, launched in 1989, provides the bulk of current data on Europa. No spacecraft has yet landed on Europa, although there have been several proposed exploration missions. The European Space Agency's Jupiter Icy Moons Explorer (Juice) is a mission to Ganymede launched on 14 April 2023, that will include two flybys of Europa.[29][30] NASA's Europa Clipper was launched on 14 October 2024.[31][32]

  1. ^ "JunoCam Image of Europa from Flyby". Jet Propulsion Laboratory.
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    "Europa". Merriam-Webster.com Dictionary. Merriam-Webster.
  4. ^ Lucchita, B. K.; Soderblom, L. A. (1982). Morrison, David; Matthews, Mildred Shapley (eds.). Satellites of Jupiter (PDF). Space science series. Tucson, Ariz: University of Arizona Press. ISBN 978-0-8165-0762-7.
  5. ^ Greenberg (2005) Europa: the ocean moon
  6. ^ "JPL HORIZONS solar system data and ephemeris computation service". Solar System Dynamics. NASA, Jet Propulsion Laboratory. Archived from the original on 7 October 2012. Retrieved 10 August 2007.
  7. ^ a b c d "Overview of Europa Facts". NASA. Archived from the original on 26 March 2014. Retrieved 27 December 2007.
  8. ^ "By the Numbers | Europa". NASA Solar System Exploration. Archived from the original on 6 May 2021. Retrieved 6 May 2021.
  9. ^ a b c d e Yeomans, Donald K. (13 July 2006). "Planetary Satellite Physical Parameters". JPL Solar System Dynamics. Archived from the original on 14 August 2009. Retrieved 5 November 2007.
  10. ^ Showman, A. P.; Malhotra, R. (1 October 1999). "The Galilean Satellites". Science. 286 (5437): 77–84. doi:10.1126/science.286.5437.77. PMID 10506564. S2CID 9492520.
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  12. ^ Bills, Bruce G. (2005). "Free and forced obliquities of the Galilean satellites of Jupiter". Icarus. 175 (1): 233–247. Bibcode:2005Icar..175..233B. doi:10.1016/j.icarus.2004.10.028. Archived from the original on 27 July 2020. Retrieved 29 June 2019.
  13. ^ a b Archinal, B. A.; Acton, C. H.; A'Hearn, M. F.; Conrad, A.; Consolmagno, G. J.; Duxbury, T.; Hestroffer, D.; Hilton, J. L.; Kirk, R. L.; Klioner, S. A.; McCarthy, D.; Meech, K.; Oberst, J.; Ping, J.; Seidelmann, P. K. (2018). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015". Celestial Mechanics and Dynamical Astronomy. 130 (3): 22. Bibcode:2018CeMDA.130...22A. doi:10.1007/s10569-017-9805-5. ISSN 0923-2958.
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  15. ^ McGrath (2009). "Atmosphere of Europa". In Pappalardo, Robert T.; McKinnon, William B.; Khurana, Krishan K. (eds.). Europa. University of Arizona Press. ISBN 978-0-8165-2844-8.
  16. ^ Chang, Kenneth (12 March 2015). "Suddenly, It Seems, Water Is Everywhere in Solar System". The New York Times. Archived from the original on 9 May 2020. Retrieved 13 March 2015.
  17. ^ Chang, Kenneth (30 September 2022). "New Europa Pictures Beamed Home by NASA's Juno Spacecraft - The space probe has been studying Jupiter since 2016 and just flew within about 200 miles of the surface of the ice-covered ocean moon". The New York Times. Archived from the original on 30 September 2022. Retrieved 30 September 2022.
  18. ^ Tritt, Charles S. (2002). "Possibility of Life on Europa". Milwaukee School of Engineering. Archived from the original on 9 June 2007. Retrieved 10 August 2007.
  19. ^ "Tidal Heating". geology.asu.edu. Archived from the original on 29 March 2006.
  20. ^ Dyches, Preston; Brown, Dwayne; Buckley, Michael (8 September 2014). "Scientists Find Evidence of 'Diving' Tectonic Plates on Europa". NASA. Archived from the original on 4 April 2019. Retrieved 8 September 2014.
  21. ^ Dyches, Preston; Brown, Dwayne (12 May 2015). "NASA Research Reveals Europa's Mystery Dark Material Could Be Sea Salt". NASA. Archived from the original on 15 May 2015. Retrieved 12 May 2015.
  22. ^ Cook, Jia-Rui C.; Gutro, Rob; Brown, Dwayne; Harrington, J. D.; Fohn, Joe (12 December 2013). "Hubble Sees Evidence of Water Vapor at Jupiter Moon". NASA. Archived from the original on 15 December 2013. Retrieved 12 December 2013.
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  29. ^ "ESA Science & Technology - JUICE". ESA. 8 November 2021. Archived from the original on 21 September 2019. Retrieved 10 November 2021.
  30. ^ Amos, Jonathan (2 May 2012). "Esa selects 1bn-euro Juice probe to Jupiter". BBC News Online. Archived from the original on 11 May 2020. Retrieved 2 May 2012.
  31. ^ "NASA's Europa Clipper". NASA. 9 April 2023. Archived from the original on 4 April 2023. Retrieved 9 April 2023.
  32. ^ Borenstein, Seth (4 March 2014). "NASA plots daring flight to Jupiter's watery moon". Associated Press. Archived from the original on 5 March 2014. Retrieved 5 March 2014.


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