Europa
Europa is the
second in size Jupiter’s satellite. It is a bit smaller than the
Earth’s Moon.
Physical parameters
of Europa:
|
|
|
diameter
[km]
|
3138
|
|
mass
[kg]
|
4.8×1022
|
|
mass
[Earth=1]
|
0.0083021
|
|
surface
gravity [Earth=1]
|
0.135
|
|
mean
distance from Jupiter
[km]
|
670900
|
|
mean
distance from Jupiter
[in Jupiter’s radiuses]
|
9.5
|
|
mean
distance from Sun
[ AU ]
|
5.203
|
|
orbital period
[days]
|
3.551181
|
|
rorational
period [days]
|
3.551181
|
|
density [g/cm3]
|
3.01
|
|
orbit eccentricity
|
0.009
|
|
orbit inclination [°]
|
0.470
|
|
orbit speed
[km/s]
|
13.74
|
|
escape
velocity [km/s]
|
2.02
|
|
visual
albedo
|
0.64
|
|
surface
chemical composition
|
water ice
|
Europa, when it
comes to the composition is similar to earth-type planets. It
consists mainly of the silicon rocks. It has a thin external ice
coat almost without the craters (there are only three craters
having 5 km in diameter!), which proves that the surface of this
moon is comparatively young and very active. There is a probability
that Europa is not completely frozen – it is possible that there is
an ocean of the liquid water under the surface of ice. The
extensive cracks, resembling the structures existing on Earth,
visible at the photos sent by the Voyager and Galileo
probes may suggest that. It is conceivable that Europa has the
metallic core.
Europa – in natural and artificial colours.
Photographed by the Galileo probe.
The latest
observations made by the Hubble Space Telescope (HST) have shown
that Europa has a very thin oxygenic atmosphere. Among many
satellites in solar system only five (Io,
Callisto, Ganymede, Titan and Triton) except Europa
have their own atmospheres. Oxygen in Europa’s atmosphere has not a
biological origin. More probable is that it came into existence as
a result of sublimation of the ice surface of the moon. A water
steam consists of hydrogen and oxygen - light hydrogen escapes from
the atmosphere and oxygen stays.
The magnetic field
of Europa is very weak and changes periodically, when it goes
through the strong field of Jupiter.
