THE SATELLITES OF SATURN

 
 

Saturn has 18 satellites: 
Atlas, Calypso, Dione, Enceladus, Epimetheus, Helene, Hyperion, Iapetus, Janus, Mimas, Pan, Pandora, Phoebe, Prometheus, Rhea, Telesto, Tethys and Titan.
 

Among these, the couples Mimas-Tethys, Enceladus-Dione and Titan-Hyperion have a gravitational interaction, producing resonance between their orbital periods: that is to say the periods have a ration of integer numbers. 
The orbital period of Mimas is half that of Tethys, the period of Enceladus is half that of Dione, the period of Titan is 3/4 that of Hyperion. 
 

The satellite Enceladus. Mosaic of pictures of Voyager 2 taken at a distance of 120,000 Km. Its surface resembles that of the jovian satellite Ganymede, with various impact craters and ridges. (NASA/JPL)

  

Image of Hyperion taken by Voyager 2 in 1981. (Calvin J. Hamilton) 
 
 

Prometheus photographed by Voyager 2 in 1981.   (Calvin J. Hamilton) 

  

Prometheus and Pandora near the F ring of Saturn.  (NASA/JPL) 
 
 

Titan

Titan is, for its dimensions, the second satellite of the Solar System, after Ganymede (satellite of Jupiter). It is even larger than planets like Mercury and Pluto.  
Titan has always interested the astronomers, because of its chemical and physical conditions. In fact, the satellite has a planetary type atmosphere, dense and rich in Nitrogen and hydrocarbons such as Methane and Ethane; the elements rich in Carbon are the constituents of the amino acids, necessary to the development of life.
The superficial temperature on Titan is approximately -178 degrees. It is thought that there is some liquid Ethane, with some Methane  dissolved in it. The superficial pressure is 1.60 atmospheres, similar to the terrestrial pressure.
The Voyager 1 probe explored the satellite in 1980, but did not succeed in studying its surface, hidden by a thick layer of clouds. In 2004 the Cassini spacecraft, which will be launched in October 1997, will reach Saturn and will release the Huygens probe,  which will descend on Titan to collect data on this satellite.
 
 

Titan photographed by Voyager in 1980. Opaque layers of clouds prevented from the observation of its surface. (Calvin J. Hamilton) 

  

Four images of Titan.  (Peter Smith, University of Arizona/NASA) 
 
Backlight image of Titan. Its atmosphere rich in Nitrogen and hydrocarbons diffuses the solar light even towards the side of the satellite that is not illuminated.  (NASA/JPL) 
  
 

Satellite Distance    Radius  Mass   Discoverer  Date of discovery   
          (x1000 km)    (km)   (kg)                 
---------  --------  ------  -------  ----------  ----------

Atlas           138      14     ?     Terrile      1980
Calypso         295      13     ?     Pascu        1980
Dione           377     560  1.05e21  Cassini      1684
Enceladus       238     260  8.40e19  Herschel     1789
Epimetheus      151      57  5.60e17  Walker       1980
Helene          377      16     ?     Laques       1980
Hyperion       1481     143  1.77e19  Bond         1848
Iapetus        3561     730  1.88e21  Cassini      1671
Janus           151      89  2.01e18  Dollfus      1966
Mimas           186     196  3.80e19  Herschel     1789
Pan             134      10     ?     Showalter    1990
Pandora         142      46  2.20e17  Collins      1980
Phoebe        12952     110  4.00e18  Pickering    1898
Prometheus      139      46  2.70e17  Collins      1980
Rhea            527     765  2.49e21  Cassini      1672
Telesto         295      15     ?     Reitsema     1980
Tethys          295     530  7.55e20  Cassini      1684
Titan          1222    2575  1.35e23   Huygens      1655
 
 
 
 


 

ANIMATIONS

Flight on Enceladus.  AVI, 3.3 Mb (NASA)
Rotation of Titan.  MPEG, 116 Kb (Calvin J. Hamilton)

 


 

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