National Geographic : 2006 Dec
"THERE'S A LAYER OF FROZEN HYDROCARBONS, SIMILAR TO GASOLINE, COVERING MUCH OF THE MOON. IF YOU COULD MINE TITAN, YOU'D NEVER HAVE TO WORRY ABOUT OIL SHORTAGES." -HUNTER WAITE, SOUTHWEST RESEARCH INSTITUTE Italian flew around like stray meteoroids, reflect ing the international origins of Huygens, which was also on display in a full-size mock-up. The real thing, moving ten times faster than a rifle bullet, had slammed into Titan's outer atmosphere just an hour earlier. Pummeled by air friction, the probe's heat shield reached a temperature of thousands of degrees. Within min utes Huygens slowed and cooled. Parachutes opened, the heat shield dropped away, and Huy gens drifted like a leaf on the winds of Titan, cameras and microphones recording the weath er on a distant world. "We'll be looking for lightning, but we might as well listen for thunder," said David South wood, head of space science for the European Space Agency, who explained Huygens's progress to the crowded auditorium in Germany. "It's going to be very romantic," said Southwood, elegant in silver hair and a dark tweed suit. As Huygens descended, people crowded into the big auditorium. Mission controllers were already receiving signals from Huygens, evidence that it had survived the descent. Relayed through Cassini, they took 67 minutes to travel from Sat urn to Earth. Finally, at 5 p.m., Southwood took the podium and formally announced the probe's safe arrival. "We are the first visitors to Titan." Now the wait began for the signals to be computer-processed into images. Hours dragged by. Suddenly a grainy black-and-white image appeared on televisions ringing the auditorium. Taken on the way down, it showed lumpy hills and a dark plain. Crowds surged toward the televisions, and the moon named for the gods commanded a moment of ritualistic, almost worshipful media attention. TV crews filmed the image of Titan. Photogra phers snapped pictures of the TV crews filming. i Deep Space Online Explore the solar system and Cassini's Saturn discoveries in an interactive Web feature at ngm.com/0612. 54 NATIONAL GEOGRAPHIC * DECEMBER 2006 Radio reporters held microphones toward the commentary coming from the sets. More images followed, including a hastily con structed mosaic showing a broad aerial pano rama. Finally the first picture from the ground appeared. This was in color-a garish orange landscape, strewn with rocks. Low hills appeared in the distance. Long into the night, crowds clus tered around the screens as they flashed the images, which had been transmitted hours before from Huygens to Cassini, stored on the mother ship, and then relayed to Earth. By that time Huygens's short mission was already over. Cassini's orbit had carried it out of contact with the lander. Huygens continued to broadcast into the void for another two hours far longer than expected-before its batteries went dead. A glitch had marred the landing. Half the pictures-350 of them-were missing because of a communications failure. Even if everything had gone perfectly, Huygens could see only a small section of Titan, much like viewing an ele phant at close range through a drinking straw. But it saw enough to answer some key questions. Beforehand, no one knew whether Huygens would touch down on solid rock or squishy goo, or in an oily methane ocean. In fact the probe found no pools of liquid, but there were plenty of signs that the surface-crusty on top, soft be low, like creme brile--is sometimes awash. "We see signs of liquid methane scouring out river valleys," says Larry Soderblom of the USGS. "Titan may be like dry African deserts, but where rain only falls every century, or even every mil lennium. But when it comes, there may be a lot, like flash floods." The poles may be rainier. On a July flyby of the northern polar region, Cassini saw a landscape dappled with methane lakes an otherworldly Minnesota. The methane originates beneath Titan's crust, brewed in deep, warm reservoirs of water and organic material or trapped in icy deposits.