A European space probe landed on the surface of Saturn's moon Titan Friday on a mission to explore its mysterious surface and hazy atmosphere — which could hold clues to how life arose on Earth.
Mission controllers know the Huygens probe made a soft landing by parachute because it is still transmitting steadily long after it had to 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 soft."
Earlier, in space, the European Space Agency's Huygens probe successfully turned itself back on, a key step in the mission, officials at mission control in Darmstadt said.
The probe was spun off from the international Cassini mother ship on Christmas Eve and began its free-fall toward the moon's surface, its systems powered down. It was to spring to life just before hitting the upper atmosphere of Titan — the only moon other than Earth's ever to be explored by spacecraft.
The probe will begin examining the gases in the atmosphere. It is also equipped with instruments to study Titan's surface upon landing, which would be the first of a spacecraft on the moon of a planet other than Earth.
"I expect it to be a very interesting and scientifically challenging moon to visit," Alan Smith, deputy head of operations at ESA, said. "The Huygens mission will be the first one to get there, that's why it's so exciting."
The spacecraft's transmissions take 67 minutes to reach Earth.
Named after Titan's discoverer, the 17th-century Dutch astronomer Christiaan Huygens, the probe is shaped like a wok and covered with a heat shield so that it that can survive the intense heat it will face upon entry.
Titan has a dense nitrogen atmosphere and chemical processes that scientists believe mirror conditions on Earth shortly after the planet's formation, says CBS News Space Consultant Bill Harwood. Given the chemical constituents, the low temperatures and high pressures at the surface, theorist predict hydrocarbon rain and, possibly, lakes or streams of ethane and related compounds on the surface. Or, perhaps, some sort of hydrocarbon sludge.
"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 20 mph.
"It could land on something solid ... it could land in liquid methane, which is what they think a lot of the black seas on Titan are," Smith said. "Because the temperature is so cold and the pressure is so high, gases like ethane and methane exist in liquid form, so it could well land in a sea of methane."
The Cassini-Huygens mission, a project of NASA, ESA and the Italian space agency, was launched on Oct. 15, 1997, from Cape Canaveral, Fla., to study Saturn, its spectacular rings and many moons.
During the nearly seven years Cassini took to reach the ringed planet, the attached probe was powered through an umbilical cable and awakened from sleep mode every six months for tests.
CBS News Space Consultant William Harwood has covered America's space program full time for nearly 20 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.