Titan’s Unexplored Country
Titan’s Unexplored Country
|Cassini’s close view of Titan from flyby. Click image for larger view. |
Image Credit: NASA/JPL
NASA’s Cassini spacecraft successfully flew by Saturn’s moon Titan at a distance of 2,402 kilometers (1,493 miles) on Thursday, March 31. Cassini’s multiple instruments are providing new views of the haze-enshrouded world.
On this recent flyby, Titan’s haze was the focus of ultraviolet observations. By mapping the haze, scientists hope to learn about particle size and properties. Titan’s transient clouds were also studied during the flyby.
Titan’s northern hemisphere was previously imaged with Cassini’s radar instrument in October 2004 and February 2005. This time, Cassini’s optical cameras got their best view of the same area, as did the visual and infrared mapping spectrometer.
This view of Titan uncovers new territory not previously seen at this resolution by Cassini’s cameras. The view is a composite of four nearly identical wide-angle camera images, all taken using a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The individual images have been combined and contrast-enhanced in such a way as to sharpen surface features and enhance overall brightness variations.
Some of the territory in this view was covered by observations made by the Cassini synthetic aperture radar in October 2004 and February 2005. At large scales, there are similarities between the views taken by the imaging science subsystem cameras and the radar results, but there also are differences.
For example, the center of the floor of the approximately 80-kilometer-wide (50-mile) crater identified by the radar team in February is relatively bright at 2.2 centimeters, the wavelength of the radar experiment, but dark in the near-infrared wavelengths used here by Cassini’s optical cameras. This brightness difference is also apparent for some of the surrounding material and could indicate differences in surface composition or roughness.
|Icy pebbles on Titan. Click image for larger view. Credit: ESA|
Such comparisons, as well as information from observations acquired by the visual and infrared mapping spectrometer at the same time as the optical camera observations, are important in trying to understand the nature of Titan’s surface materials.
Titan is a prime target of the Cassini-Huygens mission because it is the only moon in our solar system with a thick, smoggy atmosphere. Cassini was launched over seven years ago and has traveled 3.55 billion kilometers (2.2 billion miles).
All 12 of Cassini’s instruments have been returning data, including tantalizing images. Recently, scientists noticed episodic interferences on the composite infrared spectrometer that were traced back to the time of orbit insertion. A mirror on the spectrometer is showing some signs of jitter. The movement may be associated with the use of the spacecraft reaction wheels, used for spacecraft pointing control. A motor on one of three sensors on the magnetospheric imaging instrument and another motor on the plasma spectrometer are also not working properly. However, a workaround has been identified for the latter. All three instruments continue to function, although with some reduced level of science data collection.
"We are working to understand why the instruments are not performing properly but it is likely to be a few weeks before we have definitive answers," said Robert T. Mitchell, Cassini program manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. "When running a mission for this long, you expect to have a few glitches. Cassini has been working remarkably well considering the duration and complexity of the mission."
Cassini’s next encounter is with Titan on April 16 at an altitude of 1,025 kilometers (637 miles). This will be Cassini’s closest flyby of Titan yet.
Listen to sounds from the microphone onboard the Huygens during its descent (wav file format, approx. 600 kB each):