Wednesday, March 28, 2007
A HEX ON SATURN
Looking at Saturn from above its north pole, with cameras that can record images from wavelengths larger than visible light and so can see through the night sky, reveals a hexagonal shape that is, according to NASA, "unlike" anything else seen in the solar system. (Note: with a little care, in a pot, you can generate a honeycomb of hexagonal convection cells, so there is some precedence for finding naturally occuring hexagonal shapes.)
This nighttime view of Saturn's north pole by the visual and infrared mapping spectrometer on NASA's Cassini orbiter reveals a dynamic, active planet at least 75 kilometers (47 miles) below the normal cloud tops seen in visible light. Clearly revealed is the bizarre six-sided hexagon feature present at the north pole.
The strong brightness of the hexagon feature indicates that it is primarily a clearing in the clouds, which extends deep into the atmosphere, at least down to the 3-bar (3-Earth atmospheres pressure) level, about 75 kilometers (47 miles) below the clouds and hazes seen in visible wavelengths.
A more detailed image of the hexagonal feature.
The shape seems to be stable over decades, since it was first noticed in pictures taken in 1980 by Voyager 1 and 2.
NASA's description is quite detailed and informative, so rather than copy more excerpts -- or everything -- from the NASA site, here are the references:
http://www.nasa.gov/mission_pages/cassini/media/cassini-20070327.html
http://www.nasa.gov/mission_pages/cassini/multimedia/pia09186.html
http://www.nasa.gov/mission_pages/cassini/multimedia/pia09185.html
NASA also made a time lapse movie, taking pictures through the atmosphere over a period of one hour:
http://www.nasa.gov/mission_pages/cassini/multimedia/pia09187.html
Here is a direct link to the time-lapse video showing the atmosphere circulating beneath the hexagon:
http://www.nasa.gov/mov/172386main_pia09187.mov
