Science a Boon or Bane

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"Jupiter II" redirects here. For the spaceship in the 1960s television series Lost in Space, see Jupiter 2. Europa True color image taken by the Galileo probe
Europa's trailing hemisphere, as seen by the Galileo spacecraft. The prominent crater in the lower right is Pwyll. Darker regions are areas where Europa's primarily water ice surface has a higher mineral content. Discovery

Discovered by Galilei, Galileo
Marius, Simon
Discovery date January 7, 1610[1]
Designations
Alternate name(s) Jupiter II
Adjective Europan
Orbital characteristics[2]
Epoch January 8, 2004
Periapsis 664 862 km[3]
Apoapsis 676 938 km[3]
Mean orbit radius 670 900 km[4]
Eccentricity 0.009[4]
Orbital period 3.551 181 d[4]
Average orbital speed 13.740 km/s[4]
Inclination 0.470° (to Jupiter's equator)[4]
Satellite of Jupiter
Physical characteristics
Mean radius 1569 km (0.245 Earths)[4]
Surface area 3.09 × 107 km2 (0.061 Earths)[5]
Volume 1.593 × 1010 km3 (0.015 Earths)[5]
Mass 4.80 × 1022 kg (0.008 Earths)[4]
Mean density 3.01 g/cm3[4]
Equatorial surface gravity 1.314 m/s2 (0.134 g)[3]
Escape velocity 2.025 km/s[3]
Rotation period Synchronous[6]
Axial tilt 0.1°[7]
Albedo 0.67 ± 0.03[8]
Surface temp.
Surface
min mean max
~50 K[9] 102 K 125 K
Apparent magnitude 5.29 (opposition)[8]
Atmosphere
Surface pressure 0.1 µPa (10-12 bar)[10]

Europa (pronounced /jʊˈroʊpə/ ( listen);[11] or as Greek Ευρώπη) is the sixth moon of the planet Jupiter, and the smallest of its four Galilean satellites. Europa was discovered in 1610 by Galileo Galilei (and possibly independently by Simon Marius), and named after a mythical Phoenician noblewoman, Europa, who was courted by Zeus and became the queen of Crete.

Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and streaks, while craters are relatively infrequent. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, which could conceivably serve as an abode for extraterrestrial life.[12] This hypothesis proposes that heat energy from tidal flexing causes the ocean to remain liquid and drives geological activity similar to plate tectonics.[13]

Although only fly-by missions have visited the moon, the intriguing characteristics of Europa have led to several ambitious exploration proposals. The Galileo mission provided the bulk of current data on Europa. A new mission to Jupiter's icy moons, the Europa Jupiter System Mission (EJSM), is proposed for a launch in 2020.[14] Conjecture on extraterrestrial life has ensured a high profile for the moon and has led to steady lobbying for future missions.[15][16] Contents

[show]

* 1 Discovery and naming
* 2 Orbit and rotation
* 3 Physical characteristics
o 3.1 Internal structure
o 3.2 Surface features
+ 3.2.1 Lineae
+ 3.2.2 Other geological features
o 3.3 Subsurface ocean
o 3.4 Atmosphere
* 4 Potential for extraterrestrial life
* 5 Exploration
o 5.1 Spacecraft proposals and cancellations
* 6 See also
* 7 References
o 7.1 Further reading
* 8 External links
* 9 References

[edit] Discovery and naming

Europa, along with Jupiter's three other largest moons, Io, Ganymede, and Callisto, was discovered by Galileo Galilei in January 1610. The first reported observation of Io was made by Galileo Galilei on January 7, 1610 using a 20x-power, refracting telescope at the University of Padua. However, in that observation, Galileo could not separate Io and Europa due to the...
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