Lakefront Landing in Crème Brûlée

Darmstadt, Germany
January 14, 2005

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Surface image from Titan shows ice blocks strewn around. Click image for larger view.
Image Credit: ESA

The European Space Agency’s Huygens probe has lifted the veil on the bizarre world of Titan. For the first time, humans have gotten a close-up look at this planet-sized moon. Previous attempts to get a glimpse of the ground on Titan have been frustrated by the thick layer of smog that shrouds the giant moon.

Huygens, scientists say, has landed in soil with the consistency of wet sand or clay – or, as John Zarnecki, the principal investigator for Huygens’ Surface Science Package, said one team member had suggested, "crème brulé." The scenery surrounding the landing site resembles a postcard panorama of undeveloped lakefront property, hand-tinted in pastel shades of orange.

It’s hardly a typical lakefront, though – and not just because everything, including the sky, is orange. For starters, the temperature on Titan averages about minus 180 Celsius (minus 292 Fahrenheit). It makes the shore of Lake Michigan on a windy night in January seem balmy by comparison.

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Slicing segmented maps from remote sensing on board Cassini. Image Credit: JPL/Space Science Institute

Then there’s the composition of the liquid in the "lake." It’s not water. On the surface of Titan, water is frozen as solid as granite. It’s more likely liquid methane or ethane, perhaps a mixture of the two. In other words, it’s a lake of liquid natural gas.

Researchers expected that, because of the high concentration of methane in Titan’s atmosphere, they would find bodies of liquid methane on the surface. Some even proposed the possibility that Titan could be covered by a global methane ocean. The latter possibility can now be crossed off the list, although it’s important to note that Huygens examined only one tiny spot on Titan. And Cassini, the orbiting spacecraft that delivered Huygens to Titan, has only made three passes by the giant moon and has looked in detail at only a few small strips of the surface. More than 40 additional flybys are planned during the 4 years of Cassini’s primary mission. It’s still possible that some other location on Titan will reveal the presence of an ocean-sized body of liquid.

The landform adjoining the lake where Huygens landed is criss-crossed with drainage channels that appear to have been cut by erosion, through the action of flowing liquid. Again, the liquid in question could not be water or even ice; more likely it is methane or ethane.

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Channel-like landscape from 16 kilometers, at 40 meters per pixel resolution during descent. Click image for larger view.
Image Credit: ESA

The surface at the point of impact appears to be coated with organic sludge. A measurement taken of the surface material by one of Huygens’ instruments just after it landed showed a high concentration of methane.

A puffy band of white can be seen along the shoreline in images taken by Huygens as it neared the ground, although it doesn’t appear in images taken from higher elevations. In describing this white material, Marty Tomasko, principal investigator for Huygens’ imaging camera, suggested that it was "pehaps a thin ground fog, possibly of methane or ethane." Other scientists look at the same scene and see the white material as surf crashing along the shore.

All of these impressions, though, are preliminary. Huygens’ science teams have had less than 24 hours to process the vast quantity of data returned by Huygens. As ESA Director of Science David Southwood put it, "You have to understand, the science is going to be done in the future, over many years. What we see is the potential."