CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Captain's Log
May 6, 2004

The Veils of Titan

Today, we have reached a turning point in our travels on approach to the ringed planet.

We have at last glimpsed the surface of the fabled world, Titan, Saturn's largest moon and the greatest single expanse of unexplored territory remaining in the Solar System today. What wondrous sights now await us on this remarkable journey we can only imagine.

Titan has long intrigued those who watch the planets. It is a Mercury-sized icy body whose surface environment may be, in some respects, more like Earth's than any other in the Solar System. Like Earth's, its atmosphere is thick and largely molecular nitrogen. Unlike Earth's, it is lacking free oxygen and is suffused with small but significant amounts of gaseous methane, ethane, propane, and other simple and not-so-simple organic materials containing hydrogen and carbon. Some of these compounds, methane and ethane, may be liquid at the surface, despite the unimaginable cold of -300 degrees Fahrenheit. And though there is no liquid water, what water does on Earth, methane does on Titan. The presence of this simple hydrocarbon as a liquid on the surface and a gas in the atmosphere gives Titan a terrestrial-like greenhouse cycle and a boost in temperature, warming its lower atmosphere. If present-day Titan could be warmed enough to melt its icy exterior, its atmosphere would bear a striking resemblance to that of early Earth, billions of years ago, prior to the emergence of life. Might Titan be a frozen, pre-biotic Earth, telling a tale littered with clues to the origins of terrestrial life long ago?

Despite the Voyager explorations of the early 1980s, the details of Titan's story remain unknown, hidden beneath an atmosphere impenetrable to the Voyager cameras. At the moment, what lies on its surface exists only in the mind's eye.

And in the mind's eye, it is a strange place indeed.

Patchy methane clouds float several miles above the icy ground. In places, large, slow-moving droplets of methane mixed with other liquid organics fall to the surface in cold but gentle rains, cutting gullies, forming rivers and cataracts, carving canyons, and filling basins, craters and other surface depressions. Imagine Lake Michigan brimming with paint thinner.

Above the methane clouds and rain lies two hundred kilometers worth of globe-enveloping red smog, making the Titan nights starless and the days eerie dark, where high noon is as dim as deep Earth twilight. Over eons, smog particles have drifted downwards, growing as they fell, to coat the surface in a blanket of organic matter. On high, steep slopes, methane rains have washed away this sludge, revealing the bright bedrock of ice. Could Xanadu, the brightest feature on Titan, be a high, methane-washed, mountain range of ice?

Occasional bolts of lightning momentarily brighten the gloomy landscape, and wind-blown waves lap the shores of hydrocarbon lakes and seas dotting the scene.

This is a rich and complex environment, where oddly familiar terrain is carved by odd and unfamiliar substances ... a fascinating, virgin world whose only rival may be the Earth itself, with sights still unseen by human eyes.

Anticipation is at its greatest. The pulse quickens, the mind races, the soul is grateful. It is a singular privilege to be standing on the threshold separating ignorance and knowing.

And that's exactly where we are.

This is exploration at its finest and is precisely why we have come to this strange and far-away place.

Step aside, Captain Kirk. This one belongs to us.

Carolyn Porco
Cassini Imaging Team Leader
Space Science Institute
Boulder, CO

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