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Nothing But the Facts About Jupiter's Moon, Europa - I

written by: Rebecca Scudder•edited by: RC Davison•updated: 8/21/2009

Just what you wanted to know about one of the most intriguing and shy places of our solar system: Europa, one of Jupiter's largest moons, but the smallest of the Galileans (Europa, Io, Callisto, and Ganymede).

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    The Facts

    1) Year discovered: 1610

    2) Discovered by: Galileo Galilei

    3) Position among Jupiter's moons: 6th satellite from the planet

    4) Size among Galilean moons: Smallest

    5) Average distance to Jupiter: 670,900 km, 416,877 miles

    6) Rotation: synchronous with Jupiter (9hr 50m 30s)

    7) Orbital period: 3days 13hr 13m 26.4s (3.551181 Earth days)

    8) Orbital Inclination to Jupiter's equator: 0.470 degrees

    9) Eccentricity: 0.009

    10) Diameter (equatorial): 3,138 km, 1,950 miles

    11) Mass: 4.80×1022 kg, 10.5821x1022 lbs

    12) Mean Density: 3,010 kg/m3, 187.908 lbs/ft3

    13) Gravity: 0.134g

    14) Escape Velocity: 2.025 km/s, 1.258 miles/s

    15) Surface temperature (average): -171C, -276F, 102K

    16) Surface pressure: 1 μPa, 10-11 bars, 9.8x10-12 atm

    17) Atmospheric composition: Almost entirely molecular oxygen (O2)

    18) Albedo: 0.67 +/- 0.03

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    What is really cool

    Europa's water sheet structure (Credit:SSE/JPL/NASA) 1) An ocean trapped under ice. Europa is covered by a water sheet estimated to be a hundred kilometers (62 miles) thick, the surface layer being frozen ice, the rest probably in liquid form.

    2) Smooth as baby skin. Europa's most prominent surface features, its lineae (lines), are a result of brightness contrast in images, between adjacent surface areas. There are no large mountains or deep ridges, and only small craters since the surface of Europa is relatively new: Between 20 and 200 million years old.

    3) Lots of oxygen, but no air to breathe. Europa's atmosphere practically consists of nothing but oxygen. This means two things: it's not breathable by human standards since Earth's atmosphere is mainly nitrogen and only 22% oxygen, and it's extremely thin. The oxygen is continuously produced from the ice surface, by way of radiolysis (radiation splits the water molecules into hydrogen and oxygen), but most of it escapes into space.

    4) A possible harbor of life. If the hypothesis of the largest part of the water sheet being in liquid form is confirmed, then the volume of water will be twice as much as Earth's oceans, and there could exist microbial life, in conditions similar to certain deep ocean areas where energy from hydrothermal vents provides organisms with energy, instead of the sun. As far we know, this is the most realistic probability for life in our solar system. A must read on the subject is Richard Greenberg's, Unmasking Europa - The Search For Life On Jupiter's Ocean Moon.What life might be like in Europa's oceans (Credit: Richard Greenberg) 

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    Unmasking Europa - The Search For Life On Jupiter's Ocean Moon, by Richard Greenberg (ISBN 978-0387479361)

Jupiter's Moon, Europa, One of the Galilean Moons

Read the facts about the fourth largest Galilean moon of Jupiter, Europa. Mythological, physical, orbital and theoretical facts about Europa are available in this series.
  1. Nothing But the Facts About Jupiter's Moon, Europa - I
  2. Nothing But the Facts About Jupiter’s Moon, Europa - II