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Tantalizing Clues in Pictures of Saturn's Moons
Aziabel writes "Titan and Dione, two of the moons orbiting Saturn, apparently aren't exactly what researchers had previously believed. Photographs taken during a flyby of the Cassini space probe this week may clarify and even overturn long-held assumptions about the surfaces of these satellites. Bright streaks on the surface of Dione, a heavily cratered moon with little atmosphere, have long been believed to be ice, noted Carolyn Porco, imaging team leader for the Cassini project from the Space Science Institute in Boulder. Images captured this week, however, appear to indicate that the bright streaks are cliffs. They may have been created by ice, but not a lot of ice remains in the area. Meanwhile, the 'ocean' on Titan may not be. Instead of a liquid body of water, the dark mass seen on the surface of the Titan may be a viscous fluid flowing onto the white 'coastline,' Parco said. Then again, the viscous fluid could be flowing down from a higher altitude, like a glacier, onto the white mass. Right now, researchers only have two-dimensional images. Stronger conclusions may be possible with the availability later of images that are more precise, or stereoscopic images that include shadows or information on altitude."
We need more missions to the gas giants..
Every time we look at these systems with a new generation of science instruments, there is a re-writing of the text books, and it will take years to untangle what Cassini is telling us now.
Great though Cassini is, I think there is an argument for doing a larger number of smaller missions, using tried-and-tested technology - for example, New Horizons to Pluto is a mere $600 million, vs the $3 billion Cassini costs, and we could have a follow up New Horizons-II mission to Uranus & several KBO's for even less..
"You lied to me! There is a Swansea!"
Looking at the Dione picture, I'm intrigued by the linear feature near Dione's terminator to the left, crossing a number of craters and irregular fractures on the surface (diagonal orientation, from upper left to lower right). It has an internal shadow on the upper right side suggesting it's some kind of ditch or canyon. Given that Dione's radius is 560 km, this canyon seems to be more than 1 km wide and 100 km long. Could that be a tectonic feature too, or is it the track of a meteorite barely touching Dione's surface instead of impacting? I'm inclined to believe the latter, since it's so straight, but I wonder what such an event might have looked like.
Maybe Cassini will obtain a closer look at this area later. It would be nice to have a 3D model of the terrain, showing elevations.