A European space probe landed safely on the surface of Saturn's moon Titan on Friday, a space official said, buoying hopes the mission would produce data that could shed light on the origins of life on Earth.
Officials were jubilant as early signals showed the probe powering up for entry, then beginning the 2 1/2-hour parachute descent during which it was to gather information that could shed light on how life arose on Earth.
Mission controllers were confident the Huygens probe made a soft landing because it was still transmitting steadily long after it should have landed, said David Southwood, the European Space Agency's science director.
"We know that it has landed based on the laws of gravity," Southwood said. "It simply cannot still be flying. It's got to be on a solid surface, and it must be soft."
Southwood said the early signal showed little more than that Huygens was still alive and the mission wouldn't be a success until a full set of data could be sent back via the Cassini mother ship orbiting Saturn.
"We still can't fully celebrate — we need to wait for the data to come from Cassini, but we have enormous faith in this mission," Southwood said.
The heart of the mission was the parachute descent, during which the probe was to take pictures and sample the atmosphere, believed to resemble that of the Earth when it was young.
Officials were optimistic because Huygens was designed to transmit for at least three minutes after landing before its batteries died and the signal had continued for more than five hours.
Early data showed that one of Huygens' experiments, designed to measure the Titanic winds, had begun to work, said Jean-Pierre Lebreton, ESA mission manager.
"We clearly have an engineering success," Lebreton said. "We are going to work very hard to convert this into a scientific success."
Mission officials — who have waited seven years for Huygens to reach its destination — had tears in their eyes as the first signal was picked up, indicating that the probe was transmitting to its mother ship, the international Cassini spacecraft.
Huygens was spun off from Cassini on Dec. 24 to begin its free-fall toward Titan, the first moon other than the Earth's to be explored by spacecraft.
Named after Titan's discoverer, the 17th century Dutch astronomer Christiaan Huygens, the probe carries instruments to explore what Titan's atmosphere is made of and find out whether it has the cold seas of liquid methane and ethane that have been theorized by scientists.
Timers inside the 705-pound probe awakened it just before it entered Titan's atmosphere. Huygens is shaped like a wok and covered with a shield to survive the intense heat of entry.
On the way down, it was to shed its heat shield and use a special camera and instruments to collect information on wind speeds and the makeup of Titan's atmosphere. The data will be transmitted back to Cassini, which will relay them to NASA's Deep Space Network in California and on to ESA controllers in Darmstadt, Germany.
Titan is the only moon in the solar system known to have a significant atmosphere. Rich in nitrogen and containing about 6 percent methane, its atmosphere is believed to be 1 1/2 times thicker than Earth's.
Alphonso Diaz, science administrator for NASA, said Titan may offer hints about the conditions under which life first arose on Earth.
"Titan is a time machine," Diaz said. "It will provide us the opportunity to look at conditions that may well have existed on Earth in the beginning. It may have preserved in a deep freeze many chemical compounds that set the stage for life on Earth."
Part of a $3.3 billion international mission to study the Saturn system, Huygens is also equipped with instruments to study Titan's surface upon landing. Scientists don't know exactly what it will hit when it lands at about 22 mph.
The probe floats and can survive a landing in methane or ethane, which exist in liquid form due to the cold — 292 degrees below zero. One hazard would be landing on a solid slope in a position that doesn't permit a strong signal back to Cassini.
Engineers at ESA are counting on the probe having at least three minutes to transmit information and images from Titan's surface, before its battery runs out or Cassini gets out of range.
The Cassini-Huygens mission, a project of NASA, ESA and the Italian space agency, was launched Oct. 15, 1997, from Cape Canaveral, Fla., to study Saturn, its rings and many moons.