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Europa (moon)

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True color image taken by the Galileo probe
Europa, as seen by the Galileo spacecraft
Discovered by G. Galilei
Marius, Simon
Discovery time January 7, 1610
Other names Jupiter II
Adjective Europan
Reference date January 8, 2004
Shortest distance from what it orbits around 664 862 km[1]
Longest distance from what it orbits around 676 938 km[1]
Avgdistance from the center of its orbital path 670 900 km[2]
How egg-shaped its orbit is
How long it takes to complete an orbit 3.551 181 d[2]
Average speed 13.740 km/s[2]
Angle above the reference plane
0.470° (to Jupiter's equator)[2]
What it orbits Jupiter
Size and Other Qualities
Average distance from its center to its surface 1569 km (0.245 Earths)[2]
Area of its surface 3.09×107 km2 (0.061 Earths)[4]
Volume inside it 1.593×1010 km3 (0.015 Earths)[4]
Mass 4.80×1022 kg (0.008 Earths)[2]
Average density 3.01 g/cm3[2]
Gravity at its surface 1.314 m/s2 (0.134 g)[1]
Slowest speed able to escape into space
("escape velocity")
2.025 km/s[1]
How long it takes to turn around one time Synchronous[5]
Angle at which it turns
(in relation to its orbit)
How much light it reflects 0.67 ± 0.03[7]
Surface temp. Min. Avg. Max.
Surface ~50 K[8] 102 K 125 K
Seeming brightness
("apparent magnitude")
5.29 (opposition)[7]
Pressure 0.1 µPa (10-12 bar)[9]

Europa is a large moon of the planet Jupiter. It is a little smaller than Earth's Moon and it is the sixth-largest moon in the solar system.

Europa's diameter is about 3000 kilometers. It probably has an iron core, and an atmosphere that's mostly oxygen. The surface is icy and very smooth. There are not a lot of craters, but there are some cracks and lines. Because the surface is so young and smooth, scientists believe that there is a liquid ocean under the surface, a so called ocean, and that it is kept warm by tidal heating.[10] In other words, Jupiter's strong gravitational pull on Europa makes it warm.[11]

The moon Europa was found by Simon Marius in December 1609. Galileo Galilei first saw the moon in January 1610 (he did not know Marius had found it). Simon Marius was the one who had the idea of the name 'Europa.'

The moon Europa is named after a princess from Greek mythology who became the first queen of Crete. However, people usually called Europa 'Jupiter II' till the middle of the 20th century.

Life on Europa

There may be alien life in Europa's subsurface ocean, life similar to that of the Antarctic Lake Vostok or in Earth's deep oceans. There is no proof, but it is possible.

At least three things are necessary for life to develop - water, organic compounds, and heat.[11] Europa has water and heat, and organic compounds can easily be found throughout the Solar System.


  1. 1.0 1.1 1.2 1.3 Calculated on the basis of other parameters
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 "Overview of Europa Facts". NASA. Retrieved 2007-12-27.
  3. "JPL HORIZONS solar system data and ephemeris computation service". Solar System Dynamics. NASA, Jet Propulsion Laboratory. Retrieved 2007-08-10.
  4. 4.0 4.1 Using the mean radius
  5. See Geissler et al. (1998) in orbit section for evidence of non-synchronous orbit.
  6. Bills, Bruce G. (2005). "Free and forced obliquities of the Galilean satellites of Jupiter". Icarus 175: 233–247. doi:10.1016/j.icarus.2004.10.028 .
  7. 7.0 7.1 Yeomans, Donald K. (2006-07-13). "Planetary Satellite Physical Parameters". JPL Solar System Dynamics. Retrieved 2007-11-05.
  8. McFadden, Lucy-Ann; Weissman, Paul; and Johnson, Torrence (2007). The Encyclopedia of the Solar System. Elsevier. pp. 432.
  9. McGrath (2009). "Atmosphere of Europa". In Pappalardo, Robert T.; McKinnon, William B.; and Khurana, Krishan K.. Europa. University of Arizona Press. ISBN 0-816-52844-6 .
  10. Greenberg, Richard; Europa: The Ocean Moon: Search for an Alien Biosphere, Springer Praxis Books, 2005
  11. 11.0 11.1 Earth Science. United States of America: Holt, Rinehart and Winston. 2001. pp. 211. ISBN 0-03-055667-8 .

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