Titan's Ghostly Arrowhead
|Saturn and rings in perspective view. Image Credit: NASA/JPL
As Cassini scientists work to understand the newly-exposed surface of Saturn's largest moon, Titan, they have found an interesting arrowhead-shaped feature, shown in the center of this synthetic aperture radar image.
The feature is approximately 30 kilometers (19 miles) across, and it is formed from two straight lines that intersect. Looking more closely, one can distinguish other linear features that seem to follow the left side of the "arrow" and perhaps interact in some way with a dark spot.
Straight lines may represent fractures or faults in the icy crust, or they may form from material that has flowed or has been shaped by wind, either recently or in the distant past.
The area shown is about 115 kilometers (71 miles) wide and 170 kilometers (106 miles) high and is located near 52 degrees north latitude and 73 degrees west longitude. This radar image is part of a larger strip of data acquired on Oct. 26, 2004, as Cassini passed Titan at a distance of 1,200 kilometers (746 miles).
|Scientists puzzle over images from Titan, Saturn's largest moon, that resemble complex landforms. Click image for larger view. Image Credit: NASA/JPL
On January 14, 2005, the Huygens probe will try to descend to the surface of Saturn's largest moon, Titan--a biochemically rich moon dominated by hydrocarbons like methane and ethane. These building blocks, along with Titan's dense atmosphere, make the descent one of the milestone events for astrobiology. For the first time, another world presents interesting weather combined with dynamic chemistry that is often compared to a colder version of the primordial Earth.
"Titan looked nothing like we were expecting," Ralph Lorenz from the University of Arizona's Lunar and Planetary Lab told Astrobiology Magazine. "It seems to be relatively free of impact craters. We see impact craters all over the solar system, and one big fear was that Titan might look like Jupiter's moon Callisto, which is this old, dead world covered in impact craters. But Titan seems to be almost free of impact craters in this little bit of the surface we've seen. That suggests that the surface has been covered up, maybe by the deposition of organic materials, maybe by weather erosion, and perhaps by volcanism. "
Titan is thought to be mostly made of ice and rock, roughly in proportions of 50/50, but with the surface more icy and the core more rocky.
The existence of linear features may represent tectonics, faults, or cryovolcanic remnants. But interpreting RADAR images is complicated. "If the surface is rough, it scatters RADAR imaging much more effectively than a smooth surface, so bright areas tend to be rougher," said Lorenz. "And it can depend on what the surface is made of. Rock is more reflective than ice, and organic materials are darker than both of those. All these factors come into play, and so you need an educated eye to understand what you're seeing in a RADAR image. "
In a little over a month, the first up close images may sort out what the surface really offers planetary scientists.
Related Web Pages
Saturn Edition, Astrobiology Magaz.
Saturn's Rings in UV
Cassini Closes In on Saturn
Saturn-- JPL Cassini Main Page
Lord of the Rings
Space Science Institute, Imaging Team Boulder, Colorado
Saturn: The Closest Pass
Where is Cassini Now?