NASA’s Cassini spacecraft has caught a glimpse of bright sunlight reflecting off vast hydrocarbon seas and lakes near the north pole of the Saturn’s moon Titan. In the past, the spacecraft had captured, separately, views of the polar seas and lakes, and the Sun glinting off them, but this is the first time both have been seen together in the same view.
Cassini caught the sunlight glinting off Titan’s seas and lakes filled with liquid methane or ethane. Image credit: NASA / JPL-Caltech / University of Arizona / University of Idaho.
Titan’s seas and lakes are mostly liquid methane and ethane. Before Cassini’s arrival at Saturn, astronomers suspected that the moon might have bodies of open liquid on its surface.
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.
On August 21, 2014, the spacecraft transmitted back to Earth an image that shows the Sun glinting off of these bodies of liquid.
The sunglint, also called a specular reflection, is the bright area near the 11 o’clock position at upper left in the image.
This mirror-like reflection, known as the specular point, is in the south of Titan’s largest sea, Kraken Mare, just north of an island archipelago separating two separate parts of the sea.
This particular sunglint was so bright as to saturate the detector of Cassini’s Visual and Infrared Mapping Spectrometer instrument, which captures the view.
The southern portion of Kraken Mare (the area surrounding the specular feature toward upper left) displays a ‘bathtub ring’ – a bright margin of evaporate deposits – which indicates that the sea was larger at some point in the past and has become smaller due to evaporation.
The deposits are material left behind after the methane and ethane liquid evaporates, somewhat akin to the saline crust on a salt flat.
The highest resolution data – the area seen immediately to the right of the sunglint – cover the labyrinth of channels that connect Kraken Mare to another large sea, Ligeia Mare.
Ligeia Mare itself is partially covered in its northern reaches by a bright, arrow-shaped complex of clouds.
The clouds are made of liquid methane droplets, and could be actively refilling the lakes with rainfall.
