Worse news emerged when the imaging team began digging into data from the camera’s supporting instruments. Huygens contained a sensor to record each time the spinning probe swept past the sun’s location in the sky. That information was supposed to record the probe’s precise orientation when it took each image. In principle, creating a map of Titan would simply be a matter of snapping each part of the mosaic into place. But the atmosphere turned out to be a lot soupier than expected, so the sun faded once Huygens sank below an altitude of 30 miles. Tomasko grimaced stoically at the news. “Maybe we came down through a methane shower,” he said.

Huygens also was buffeted by those high winds that Gurvits measured. “We had a hell of a ride,” said Laura Ellen Dafoe, lead systems engineer of the Huygens optical package. “We prepared for a 10-degree tip, but we got a 60-degree tip.” Every picture therefore arrived with almost no information about where the camera was pointed.

“It’s like trying to assemble a jigsaw puzzle without half the pieces and with no picture on the box,” Tomasko said. With the reporters and TV crews waiting, the imaging team huddled around their computers to reconstruct meaningful views of Titan. The first night after Titan’s Saturday landing, Tomasko released three individual frames—“raw images, hot off the computer”—that gave intriguing glimpses of riverbeds, a dark coastline, and Titan’s pebble-strewn surface. Sunday he and his teammates hunkered down in their temporary headquarters, a pair of connected trailers plopped in a weedy courtyard next door to the control room, and the second frenzy began.

While the telephone kept ringing—When will we see more pictures? Can you do an interview?—the researchers ricocheted between glee and disappointment, divided up the tasks, and tore into the work. One group cleaned up the images; another tried to deduce the color of the surface; yet another sifted for directional clues buried in the probe’s readings of scattered sunlight. Tomasko puzzled over the nature of Titan’s haze while Laurence Soderblom of the U.S. Geological Survey, a geologist on the team, dissected the geometry of the images. Soderblom groaned good-naturedly at his task: “It’s the arithmetic that kills you.”

By Tuesday giddy grins appeared in the makeshift imaging lab. “Yesterday was the worst day,” said Lisa McFarlane, a postdoc at the University of Arizona. Using improvised computer programs, she had started to figure out Huygens’s orientation at the time of each snapshot, which made it much easier to construct large panoramas of Titan’s surface. Soderblom had pinpointed the probe’s landing site. Tomasko could finally relax and put his worst fears in the past tense: “We came so close to losing everything.”

Few people outside of Tomasko’s group knew about the restless problem solving, number crunching, and seat-of-the-pants programming that followed the Huygens landing. Everyone could see the triumphant result. NASA and the European Space Agency released an imposing mosaic view of Titan’s surface, a version of the Titanian road map that came together, piece by piece, on the trailer’s wall. Three days earlier, Titan was a celestial question mark. Now it was succumbing to geologists, chemists, and cartographers, much as the Antarctic had a century earlier.

With each refinement, the picture looked more and more like a world we already knew. “Titan was supposed to be bizarre,” said Soderblom. “Instead it’s the most Earth-like planet in the solar system.” (Calling Titan a planet is a telling slip. Technically it is a satellite, but everyone on the Huygens team regards Titan as the equal of Mars, which is only slightly larger and has much less atmosphere.)

The bright highlands are most likely outcroppings of water ice. On his laptop computer in the trailer, Soderblom compared stereo images of the hills and estimated that they are a few hundred feet high. Organic soot steadily settles out of Titan’s atmosphere, so something—possibly methane rain—must scour these light areas clean. Dirty runoff evidently flows into the branching channels seen in the first-released Titan image. The channels lead to dark, flat lowlands—lake beds, perhaps.

Much to Tomasko’s frustration, the Huygens images did not clearly show whether any of the lakes contain liquid right now. On the other hand, everyone on the imaging team was overwhelmed by the evidence for rainfall and flooding in the relatively recent past. Soderblom pointed to formations that look like sandbars and barrier islands. The view from the surface shows rounded blocks of water ice, like eroded stones in a creek bed. One set of images shows patchy fog, which could be subsurface methane evaporating into the atmosphere; another reveals what looks like channels flowing outward from a methane spring. “This is an active, young surface,” Soderblom said.

An onboard accelerometer and ground penetrometer kicked in additional hints about the nature of the ground where Huygens landed. John Zarnecki of the Open University in the United Kingdom, who led the experiment, reported that the 705-pound Huygens, falling 10 miles per hour, first broke through a relatively stiff layer, about half an inch thick, then sank about six inches. An icy crust atop a muddy mix of water-ice “sand” and liquid methane would match the readings nicely. As Zarnecki watched workers dismantle the conference table where he had presented these results, he was already formulating plans to drop a test target into various combinations of sand, mud, and gravel to simulate Titan’s surface texture.

Results from one of Huygens’s chemical sniffers bolstered the idea that the probe landed on soil that had recently been soaked with methane dew or rain. About three minutes after the probe landed, it picked up a tendril of methane wafting from the surface, as if the probe’s heat were boiling some of the liquid trapped just below. Traces of argon gas found in the atmosphere, along with radar readings from Cassini, even hint at volcanic activity. At Titan’s frigid temperatures, however, the lava would be a syrupy mix of water ice and ammonia.

“Titan is a strange, through-the-looking-glass kind of world,” Tomasko said. The description fits not just its appearance but also its chemistry. Four billion years ago, Earth’s atmosphere might have broadly resembled the one Titan has today. Cold, sluggish Titan has evolved much more slowly, so the dirty orange organic chemicals that tint its surface—most likely dominated by tarry compounds called tholins—could be a deep-freeze model of early Earth.

Guy Israel of the University of Paris has been decoding the chemical brew Huygens encountered during its descent. He hardly expects to find signs of life. Biochemistry as we know it relies on reactions that can happen only in solution, “and that is not a possibility—unless we bring along the liquid water,” he said.

By the end of the week, officials at the European Space Agency were already looking forward to their next missions, to the moon and Venus, but the researchers in Darmstadt couldn’t escape the spell of Titan, a world that looks and acts so much like our own. Even as they began scattering to their homes in Arizona, Paris, London, and Bonn, the Huygens scientists were dreaming about how to return. Tomasko was tantalized by Titan’s dense atmosphere and luxuriously low gravity: “It would be a wonderful place to explore with a balloon.”