The Cassini spacecraft orbiting Saturn has seen light reflecting off Kraken Mare, a giant hydrocarbon lake on the distant satellite of Titan. This new image, taken on August 21, 2014, is the first dramatic photo of the precipitation cycle on an alien satellite.
Sunlight coming from the north polar sea bounced off the surface of the liquid body, and to the waiting observatory. An infrared camera on board the vehicle captured the sea, and sunlight reflecting from the body, for the first time ever.
Lakes on Titan are composed largely of methane and ethane, two fairly common chemicals here on Earth.
Methane clouds, shaped like an arrow, are also seen in the photograph. These formations may be acting like rain clouds, replacing hydrocarbons in the alien lake. Surrounding the basin which holds the liquid is a "bright margin," which is similar to an over-sized bathtub ring. This feature provides evidence the lake may have once been higher in the past than it is today.
"The deposits are material left behind after the methane & ethane liquid evaporates, somewhat akin to the saline crust on a salt flat," Cassini mission planners reported in a press release announcing the new image.
Titan is the largest moon of Saturn, and the only satellite in the solar system known to possess a significant atmosphere. Before the arrival of Cassini in the Saturnian system, astronomers believed the giant moon, 1,600 miles across, might hold oceans of hydrocarbons. What they discovered was a surprise to researchers.
"Cassini found only great fields of sand dunes near the equator and lower latitudes, but located lakes and seas near the poles, particularly in the north," Jet Propulsion Laboratory engineers wrote on their Web site.
Specular reflection, the glint of sunlight off the lake, located in the southern region of Titan's north polar sea, was so bright it overwhelmed the sensitive camera on-board the spacecraft.
Human eyes looking at Titan from the standpoint of Cassini would see nothing but a featureless haze. A trio of wavelengths which could penetrate the atmosphere were assigned to the primary colors, and used to create the composite image.
Water cannot exist in liquid form on the frozen surface of Titan. However, methane acts on that world much as water does on Earth, forming lakes and rivers and deltas. Temperatures on the alien satellite can reach -289 degrees Fahrenheit.
Cassini was launched in October 1997, and reached Saturn in July 2004. The spacecraft, designed to last just four years, has been delivering new discoveries for over a decade.