Wednesday, October 26, 2005

The Prometheus Effect

The Cassini Spacecraft has taken high resolution images of the F-ring and have figured out how the small moon Prometheus causes the structure seen in the F-ring using a simple dynamical model. A paper is being published in the next issue of Nature if you want more details than you can find on the web.

I went to a talk yesterday about Enceladus and the rings of Saturn that was very interesting as well. The Ultraviolet Imaging Spectrograph on board Cassini has imaged a torus of molecular oxygen at the distance of Enceladus and after recent flyby's of Enceladus, have found that the south pole of the moon is warmer by 20 degrees than the equatorial region. Their hypothesis explaining their observations suggests that liquid water under a cracked surface on the younger south pole (compared to the cratered and obviously older surface elsewhere on the moon) is venting through the cracks with water perhaps mixed with ammonia that would be around 170 degrees Kelvin and liquid below the surface, would raise the temperature of the surface around the cracks to about 85K from about 65K as it cools to about 140K as it sputters Old Faithfull style into space, creating an atmosphere that escapes the moon and forms the oxygen torus as well as the water dissociates. The talk culminated in a discussion of the rings and it sounds like if the rings are regenerative, they could be much older than recent estimates, perhaps billions of years rather than only millions. They actually try to measure the ratio of icy ring material to contaminants from impacting meteoritic material as one estimate of age of the rings, but different ring models result in rather wide ranges of ages for the rings. Maybe they'll figure things out by the time Cassini's mission is complete. But in any case, it's really neat to see science and our knowledge of the Saturnian system growing by leaps and bounds as Cassini orbits the 2nd largest planet in our solar system. And another Titan flyby is on schedule shortly too!


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