Titan image small (41K): antwrp.gsfc.nasa.gov
Titan image big (525k): antwrp.gsfc.nasa.gov
Titan landing zone (34k): antwrp.gsfc.nasa.gov
Huygens Probe to Attempt Landing on Saturn Moon
Chicago Tribune
CHICAGO - The scientists have been anxiously awaiting this moment for seven years, their $700 million gamble whittled now to 153 tense minutes Friday morning.
In that time, if all goes right, a European probe just bigger than a riding lawn mower will parachute through 186 miles of hazy atmosphere to the frigid surface of Saturn's largest moon, Titan.
Finding life there is unlikely, but possible, scientists say. It is already known that Titan contains the same building blocks and likely the atmospheric processes that made organic chemistry possible on Earth. By studying Titan, the probe could help explain the early Earth.
Most of the rest is uncertainty. NASA's Cassini orbiter, which brought the Huygens probe to Saturn, employs sophisticated imaging equipment, but failed to see much through Titan's thick orange atmosphere even after several close looks.
"You have the feeling there's something really interesting on the surface," said Martin Tomasko, an Arizona investigator who puzzled over light and dark patches Cassini saw on Titan, and who will now look for better views of the "new world" he believes lies hidden by the moon's smog.
If all works, the first glimpse of it will come in Germany, where jet-lagged and tense scientists at the European Space Agency headquarters outside Frankfurt are staring at blank computer screens waiting for streams of numbers expected from Titan. Others are watching in the Jet Propulsion Laboratory in Pasadena, Calif., where, if all goes right, the first information will appear at 7 a.m.
Radio telescopes in Australia have their dishes pointed at Titan, listening for echoes from the European-built probe as it falls. Web sites have updated astronomy buffs on Huygens' progress toward Titan for weeks.
So far, planetary scientists have based their understanding of the moon, which is nearly the size of Mars, on unsatisfying pictures taken by passing spacecraft.
Pioneer 11 passed in 1979, followed in 1980 by Voyager 1, which found a nitrogen atmosphere churning methane clouds into more complex carbon-based molecules. Cassini took the most recent pictures and will now relay Huygens' finds to Earth.
Until now, conditions on the Saturnian moon could be explored only in laboratories and imaginations.
It is a world where the air is minus 290 degrees Fahrenheit, where water is frozen solid and where conditions seem promising for finding liquid ethane _ a colorless gas on Earth consisting of two carbon atoms surrounded by six hydrogen atoms.
Carbon atoms form the skeleton of all organic molecules, which in combination are the essential components of known forms of life.
Observations and lab experiments show that Titan's atmosphere forms ethane, as well as carbon-based methane and acetylene, which likely condense into droplets and fall either as rain or as a sticky ash. Layers of it are thought to cover much of the moon.
Discoveries earlier in the Cassini-Huygens mission have raised suspicions among scientists that organic compounds are more common in the outer solar system than earlier thought - perhaps more common there than among inner planets, said Lunine.
Huygens will try to confirm some of those suspicions, mostly during its descent. Unsure it would survive a landing, scientists piled atmospheric experiments onto Huygens that will relay data to Cassini as it is collected.
Among the things scientists would like to learn is how the moon replenishes its atmospheric methane, an organic molecule thought to be split by solar radiation into other organic compounds that scientists expect to find.
Nitrogen-rich compounds in Titan's atmosphere - including ammonia - make another inviting target for investigation. Huygens' cameras will seek active volcanoes that could spew nitrogenous gases into the sky, as well as suspected lakes of ethane and methane long postulated but never discovered.
Deciphering what Huygens finds will take months, though scientists hope to develop at least a few images of Titan's surface within hours of receiving information from the probe.
After that, said Tomasko, "I hope to get out of the speculation business and into the measurement business."
His hopes depend on Huygens hitting its mark above Titan's southern hemisphere, three alarm clocks waking the slumbering probe in time and its heat shield separating in time. Three parachutes, one after another, will need to deploy without a hitch.
Cassini will relay Huygens' finds - if the probe can send any - back to Earth, a 67-minute journey at the speed of light across some 750 million miles. Scientists won't know if the mission has survived until hours after its fate will have been decided on Titan.
The Cassini-Huygens mission, developed by NASA, the European Space Agency and the Italian space agency, was launched in 1997 and needed four close passes by other planets - each flinging the craft toward the next - to gather the speed to reach Saturn last July.
On Dec. 25, explosive bolts released the 700-pound Huygens probe. The orbiter snapped a final picture of the probe moments later, spinning slowly on its final three-week coast to Titan. |
