Cassini at Enceladus
 Water vapor streams into space from the south pole of Enceladus, one of the moons of Saturn, in this October 2007 image from the Cassini spacecraft. Cassini will fly just above the moon's south pole on March 12, providing the best view to date of the source of the water plumes: cracks in Enceladus' icy crust. Cassini may briefly pass through the plume of water vapor, which freezes in the cold of space. [NASA/JPL/SSI]
But if all goes well, Cassini's most impressive encounter yet may come tomorrow. The craft is scheduled to fly just a few miles above the south pole of the moon Enceladus. Scientists are particularly excited about the low pass because at that altitude, Cassini may fly through plumes of water that are jetting out from below the moon's icy crust.
Cassini spotted the plumes a couple of years ago. They came as quite a surprise, because Enceladus is bitterly cold -- its surface temperature is around 330 degrees below zero Fahrenheit.
Cassini also found that the moon's surface is cracked. Long parallel grooves form "tiger stripes" around the south pole. And that's where the water's coming from. Something is heating the layers just below the surface, melting some of the ice and cracking the crust. The warm water squirts into space and freezes. Some of these little drops of ice escape Enceladus and form one of Saturn's rings.
There was some concern that bits of ice could hit Cassini and damage the craft. But scientists decided that the odds are against such a collision, and the scientific rewards -- not to mention the view -- are worth the risk.
More about Enceladus tomorrow.
Script by Damond Benningfield, Copyright 2008
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
|
Contact | About | Friends of McDonald | Sign up for Sky Tips
