October 24, 2013
Saturn’s Moon Titan Shows Off In New Cassini Image
April Flowers for redOrbit.com - Your Universe Online
The sun is now shining down over the northern pole of Saturn's moon, Titan. Combine that with a bit of lucky weather and trajectories that put the spacecraft into optimal viewing positions, and NASA's Cassini spacecraft has obtained new pictures of the liquid methane and ethane lakes and seas near the moon's north pole. New clues about the formation of the lakes, and the Earth-like "hydrologic" cycle, which involves hydrocarbons rather than water, are revealed in the images.At Titan's south pole there is one large lake and a few smaller ones. However, almost all of the lakes on Titan appear at the north pole. Using radar that can penetrate beneath Titan's clouds and thick haze, scientists have been able to use Cassini to study much of the terrain. Previously, only distant, oblique or partial views of the north pole have been captured by Cassini's visual and infrared mapping spectrometer.
It took several factors combined to give these instruments such great observing opportunities. Better viewing geometry was provided during two recent flybys. The winter darkness that surrounded Titan's north pole since Cassini arrived nine years ago has begun to be pierced by sunlight, while a thick cap of haze has also dissipated as the northern summer approaches. The beautiful, nearly cloudless, rain-free weather of Titan also continued during Cassini's flybys this summer.
Mosaics in infrared light, these images were created from data collected during flybys on July 10, July 26, and Sept. 12, 2013. The visual and infrared mapping spectrometer, which maps infrared colors onto the visible-color spectrum, created a colorized mosaic that reveals differences in the composition of material around the lakes. The data collected from this instrument suggests that parts of Titan's lakes and seas may have evaporated and left behind the Titan equivalent of Earth's salt flats. On Titan, however, the evaporated material is thought to be organic chemicals originally from Titan's haze particles that once dissolved in liquid methane. In the image, they appear as orange against the greenish background of Titan's typical bedrock of water ice.
"The view from Cassini's visual and infrared mapping spectrometer gives us a holistic view of an area that we'd only seen in bits and pieces before and at a lower resolution," said Jason Barnes, a participating scientist for the instrument at the University of Idaho, Moscow. "It turns out that Titan's north pole is even more interesting than we thought, with a complex interplay of liquids in lakes and seas and deposits left from the evaporation of past lakes and seas."
Previously invisible in the data, a bright unit of terrain in the northern land of lakes was revealed by Cassini's near-infrared imaging cameras. The bright area suggests to scientists that the surface of Titan is unique here, which might explain the lakes in this area. A variety of formation mechanisms have been suggested for the lakes on Titan, which have very distinctive shapes - rounded cookie-cutter silhouettes and steep sides. These theories range from the collapse of land after a volcanic eruption to karst terrain, where liquids dissolve soluble bedrock. Karst terrains on Earth can create spectacular topography such as the Carlsbad Caverns in New Mexico.
"Ever since the lakes and seas were discovered, we've been wondering why they're concentrated at high northern latitudes," said Elizabeth (Zibi) Turtle, a Cassini imaging team associate based at the Johns Hopkins Applied Physics Laboratory, Laurel, Md. "So, seeing that there's something special about the surface in this region is a big clue to help narrow down the possible explanations."
Cassini has been exploring the Saturn system since 2004. A full Saturn year is 30 Earth years, and so far, Cassini has been able to observe nearly a third of a Saturn year, during which time, Saturn and its moons have seen the seasons change from northern winter to northern summer.