Saturn

Key points: Comparison of Saturn with Jupiter; comparison of Uranus and Neptune with the former two

saturn_cassini.jpg (17043 bytes)

saturn-shani.jpg (20162 bytes)

(to left, from NASA, Cassini Project; above, Shani, the planet Saturn, from from The Black Peacock, http://www.goloka.com/index.html))
A different view. A solar eclipse by Saturn, viewed by the Cassini spacecraft. The earth is the tiny dot just outside the bright rings at about the 10 o'clock position. The night-time cloud tops on Saturn are lit up by light scattered by the rings. The outermost fuzzy ring that fills the picture is fed by ice fountains where material is escaping from the moon Enceladus. (CICLOPS, JPL, ESA, NASA, vis APOD: http://apod.nasa.gov/apod/ap061016.html)

 

 saturneclipse.jpg (43373 bytes)
gianplan.jpg (148474 bytes) Saturn, another giant planet, is very similar to Jupiter in many respects:
  • Its composition is mainly H and He
  • It rotates very rapidly, in 10 and half hours
  • It is large, with very low density
  • Its atmosphere has colored bands, high winds, violent storms
  • It has an internal energy source (but why is it so strong; Saturn being smaller than Jupiter should have cooled off more) 

Saturn differs from Jupiter in ways that reflect either its lower temperature or smaller size:

  • Atmospheric bands have weaker coloring due to lower temperatures
  • Weaker magnetic field due to a smaller proportion of metallic hydrogen in its interior

(from Nick Strobel's Astronomy Notes. from www.astronomynotes.com )

Artist's concept of flying through Saturn's clouds
Storms on Saturn; the cloud patterns are similar to those on Jupiter but more subdued in color in the visible. The infrared picture to the left has been processed to bring out the detail in a huge storm at the planet's north pole (Cassini-Huygens, http://apod.nasa.gov/apod/ap130502.html). To the right is an artist's impression of the view over Saturn's cloud tops (right; Don Dixon)

Uranus and Neptune

Uranus

Neptune

(http://www.mira.org/fts0/planets/100/text/txt003x.htm)

 Uranus Neptune
gianplan.jpg (148474 bytes)
  • have modest magnetic fields
  • internal structure differs from Saturn and Jupiter because these planets are too small to compress H to the metallic state.
  • may contain a substantial icy water layer that generates their magnetic fields

 

(from Nick Strobel's Astronomy Notes. from www.astronomynotes.com )

But the two planets are not completely identical:

Bands show Uranus' axial tilt  
  • As shown by the bands in its atmosphere, Uranus has a curious tilt of its rotational axis (nearly in the plane of its orbit; a pole will be sun lit for 42 years at a time!).

Nonetheless, the surface temperature is uniform implying that winds stir the atmosphere.

(http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-uranus.html)