Titan's Huge Crater from Radar
|Titan seen in different filters tuned for atmospheric depths. Click image for larger view.
Image Credit: Keck
A giant impact crater the size of Iowa was spotted on Saturn's moon Titan by NASA's Cassini radar instrument during Tuesday's Titan flyby.
Cassini flew within 1,577 kilometers (980 miles) of Titan's surface and its radar instrument took detailed images of the surface. This is the third close Titan flyby of the mission, which began in July 2004, and only the second time the radar instrument has examined Titan. Scientists see some things that look familiar, along with scenes that are completely new.
"It's reassuring to look at two parts of Titan and see similar things," said Dr. Jonathan Lunine, Cassini interdisciplinary scientist from the University of Arizona, Tucson. "At the same time, there are new and strange things."
|"Cat scratch" marks seen in Titan radar image. Click for larger view
Image Credit: NASA/JPL
This flyby is the first time that Cassini's radar and the imaging camera overlapped. This overlap in coverage should be able to provide more information about the surface features than either technique alone. The 440-kilometer-wide (273-mile) crater identified by the radar instrument was seen before with Cassini's imaging cameras, but not in this detail.
A huge annular feature with an outer diameter of approximately 440 kilometers (273 miles) appears in this image taken with Cassini's Titan radar mapper. It resembles a large crater or part of a ringed basin, either of which could be formed when a comet or asteroid tens of kilometers in size slammed into Titan. This is the first impact feature identified in radar images of Titan.
The surface of Titan appears to be very young compared to other Saturnian satellites. In Titan's case, debris raining down from the atmosphere or other geologic processes may mask or remove the craters. The pattern of brightness suggests that there is topography associated with this feature; for example, in the center of the image there appear to be mounds each about 25 kilometers (15 miles) across. Since they are dark on their lower edges that face away from the radar and bright on the opposite face, they must be elevated above the surrounding terrain.
|First close view of Enceladus' bright surface. Click for larger view
Image Credit: NASA/JPL
A second radar image released today shows features nicknamed "cat scratches". These parallel linear features are intriguing, and may be formed by winds, like sand dunes, or by other geological processes.
The frame, measuring about 300 kilometers (186 miles) from top to bottom, shows an area near the northeast corner of the large optically bright region named Xanadu.
Running across the image are a series of roughly parallel, mostly east-west dark linear features that join and separate, which are not seen in the previous radar images. They may be formed by the action of eastward-flowing winds, or geologic processes acting on the crust itself. In places they cut through adjacent terrain, while elsewhere the lineaments seem to be interrupted by brighter material, appearing again on the other side. Seams between radar segments are visible as horizontal, sawtooth-shaped lines.
Bright material in radar images may be rough or sloped toward the radar (which is observing from the top in this frame). Also, some of what is seen may in fact be below the surface, revealed as the radio waves penetrate overlying, radar-transparent material.
On Thursday, Cassini conducted its first close flyby of Saturn's icy moon Enceladus (en-SELL-uh-duss) at a distance of approximately 1,180 kilometers (730 miles). Enceladus is one of the most reflective objects in the solar system, so bright that its surface resembles freshly fallen snow. Cassini's flyby of Enceladus is the closest ever by any spacecraft.
Listen to sounds from the microphone onboard the Huygens during its descent (wav file format, approx. 600 kB each):
Related Web Pages
Rendezvous with Titan
Huygens, Phone Home
Saturn-- JPL Cassini Main Page
Space Science Institute
Where is Cassini Now?
Did Fluid Once Flow on Titan?