Ligeia Mare, shown here in a false-colour image from the international Cassini mission, is the second largest known body of liquid on Saturn's moon Titan.
It measures roughly 420 km x 350 km and its shorelines extend for over 3,000 km. It is filled with liquid hydrocarbons, such as ethane and methane, and is one of the many seas and lakes that bejewel Titan's north polar region.
Many rivers can be seen draining into the sea. Cassini has yet to observe waves on Ligeia Mare but they may appear later, as Titan’s north polar region approaches summer solstice in 2017 and the winds gets stronger. While estimates of wind speeds on Titan vary, most scientists agree that winds are currently too calm to make waves at Ligeia’s latitude. Data for precise measurements of Ligeia Mare’s surface roughness were collected during the spacecraft’s recent flyby of Titan on 23 May 2013 and will provide more clues.
The mosaic shown here is composed from synthetic aperture radar images from flybys obtained between February 2006 and April 2007.
This imaging technique works by collecting the echoes from radar pulses sent to the surface of Titan by Cassini. By breaking the echoes up by time and frequency, an image of the surface can be constructed using a technique known as Synthetic Aperture Radar (SAR). The overall intensity of the return echo is dependent on the roughness, structure, and composition of the surface. In the case of SAR imaging, smooth surfaces appear dark since most of the transmitted energy is reflected away from the spacecraft. In this image, smooth areas such as Ligeia Mare reflect little radar and are coloured black. By contrast, rough areas scatter more energy back toward the radar and are depicted here in yellow to white in the false colour representation. Because the radar operates at a single frequency, radar images actually do not contain “colour” (or frequency-dependent) information.
Radar provides a way to ‘see’ through the thick atmosphere that blurs Titan’s surface in visible and infrared images.
Several alternate versions of this image are available here.
The Cassini–Huygens mission is a cooperative project of NASA, ESA and ASI, the Italian space agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and ASI, working with team members from the US and several European countries.