Titan and the Lakefront?


Carolyn Porco, Imaging Team Lead. Image Credit: NASA/JPL

Two days away from a year in orbit and Titan, the body fantastic of Saturn, exotic enough to intrigue yet familiar enough to offer the promise of comprehension, has yielded many a startling revelation.

Last January was most startling of all. In a spell-binding and historic first, an aerodynamically shaped flying saucer of our own making, carried by Cassini for seven years across the depths of interplanetary space, successfully drifted on a piece of fabric through the dim hazy atmosphere of Titan and came to permanent rest on its surface.

We humans had firmly arrived in the outer solar system … ten times farther from the Sun than the Earth, and seven times farther than we had ever landed anything else before. We might as well have traveled to an alien body orbiting a distant star in some other quadrant of our galaxy … the sense of exploration has been no less.

The mythic landing of the Huygens probe on the cold, dark equatorial plains of Titan is already the stuff of legend.

What it has shown us of Titan’s near-surface environment — the stunning, unambiguous dendritic patterns carved by flowing fluid, the presence of liquid methane suffusing an unconsolidated ground having the mechanical properties of wet sand, pebbles of solid water ice scattered across a flattened landscape created possibly by once-flowing rivers, and more — has been used to great advantage in the interpretation of the views of Titan’s surface seen through our cameras flying high overhead.

And fly we did. In the months since Huygens’ arrival, we have orbited Saturn nine times, have five times encountered Titan at close range, and have had scraping encounters with Saturn’s icy moons.

Titan’s dark region that appears lake-like. Click image for larger view.
Image Credit: NASA/JPL

We’ve caught the undulating currents on Saturn, discovered a new moon clearing an opening in its outer rings, and captured giant convective storms rising high through the planet’s deep atmosphere and hissing loudly with the radio static of lightning.

We have lingered on regal Saturn, embraced by tendril shadows. At times, we have shot glances across its seemingly paper-thin rings to see looming Titan, sun-drenched Rhea, and the planet itself looking serene and magically ringless. We have beheld the shifting hazes which crown the north Titan pole, peered beyond the torturous surface of bright white Enceladus, and captured the portraits and balletic motions of sibling moons.

And we have witnessed sights of stark unsurpassed beauty, at once surreal, grand, heart-breakingly lovely and deceptively improbable, that life in orbit around the ringed planet has brought.

A handful of encounters with Titan have thus far shown us a remarkable body, with a colorful atmosphere and a variegated geography formed by tectonics, winds, few impacts, and running liquid. All this while, we have not seen a single clear sign of open bodies of liquid anywhere on the moon.

Cloud formation on Titan near the lake. Click image for larger view. Credit: NASA/JPL/Space Science Institute

Now, a dark surface marking at high southern latitude has come into focus and we are riveted.

Darker than anything immediately around it, its outline is familiar … like the fresh water shorelines of Earth we might have played on as children on a summer’s day. Titan summer, however, is -300 degrees F, and it is not water filling this striking feature. Located in the cloudiest region of Titan and presumably the most likely place to find depressions filled by methane rains, this feature, the size of Lake Ontario, has set imaginations aflame. Could this be one of the fabled bodies of liquid hydrocarbons believed, prior to Cassini, to dot the Titan landscape? Or even perhaps a dried lake-bed, once filled to brimming with the Titan equivalent of paint thinner, and now caked with the solid residue left behind by methane evaporation?

Further examination and, hopefully, future opportunities to observe this fascinating feature should tell the tale.

In the meantime, we savor our good fortune to be coursing among the exotic inhabitants of the enchanting realm of Saturn.

You can listen to sounds from the microphone onboard the Huygens during its descent (wav file format, approx. 600 kB each) at the European Space Agency’s "Sounds of an Alien World site" at: http://www.esa.int/esaMI/Cassini-Huygens/SEM85Q71Y3E_0.html.

An animation tracking the landing of the Huygens probe on Titan is available from NASA at: http://www.nasaimages.org/luna/servlet/detail/NVA2~1~1~2348~102521:Tracking-Huygens-Animation