Wednesday, July 05, 2006
The color images from the Cassini page are close approximations of what the human eye would see in the Saturnian neighborhood. The spacecraft can detect radiation at certain wavelengths in order to see details an ordinary camera would miss. Certain gases appear either transparent, bright or opaque in certain colors or in the infrared (heat) or ultraviolet. Scientists can then peer beneath certain layers of gases, finding out what's under the hazes of the father planet and it's main moon Titan. When the Cassini team combines visible light scans--in this example on the right, it's red, green and blue filtered--they get a color image a space traveler would recognize. That black bar in the middle is the line of Saturn's rings blotted out by the planet. Their shadows are seen above that as those angled "chunks" up north. The important color finding thus far for Saturn is that its northern (winter) hemisphere appears more blue than gold. Nobody's quite sure why. Ring shadows aren't thought to make that much of a difference, as Saturn generates heat for its weather from the interior, and doesn't rely as much (so it is thought) on solar heating. By the way, the rings would block that view of blue clouds from Earth's telescopes--the reason why we've never seen it before Cassini. Keen eyes have discerned subtle pinks and greens as well in the planet's clouds. Saturn isn't nearly as volatile as Jupiter so the tints are faint and elusive. One reason is that it's a bit cooler at a distance of 880 million miles from the sun--compared with 480 million at Jupiter. Atmospheres churn when there's heat, and you'd have to go below the golden clouds to find upheaval on the 6th planet. It's there; we just don't see it. We think. Anyway, this link gives you a bit more of the story. Feel free to click the Cassini link on my sidebar to check out the latest news and images from the Saturn probe.