The Saturn orbiter Cassini, which acted as the relay station for Huygens, sent back signals showing that it had finished its retrievals from Huygens and had turned toward Earth to begin transmission of a likely three hours of data.
Huygens began its two-hour descent through Titan's atmosphere to the surface in the early morning after a seven-year journey piggybacked on the Cassini space probe and a final one-way trip of about three weeks on its own.
The probe soon began transmitting a signal to scientists monitoring its progress at the European Space Agency's Space Operations Center in Darmstadt, Germany, and NASA's Jet Propulsion Laboratory in Pasadena.
That carrier signal did not return data, but indicated the probe had switched on its transmitter, deployed its parachute and was descending to the surface in good health.
The transmission of the signal, which scientists compared to a dial tone, continued strong for the next two hours, giving the team hope that Huygens' six instruments and camera were taking in the sights and sounds of Titan.
"Because of this, we can look in the sky and when we see Saturn we can say 'We've been there, we've left our mark,"' said Carolyn Porco, leader of the Cassini imaging science team, in a live ESA broadcast on NASA TV. "I'm looking forward to another decade of exploration and this is only the beginning."
Scientists said it appeared Huygens survived on the surface of Titan for at least 90 minutes. While it may have continued transmitting, at some point it lost communications with Cassini when the Saturn probe turned to Earth.
Cassini will record the data from Huygens on four redundant systems.
"This is a safety measure. We really don't want to lose any beat of this very, very precious data," said Claudio Sollazzo, head of Huygens operations for the ESA. Sollazzo said they expected data on the probe's descent before getting any indications about the little-known surface of Titan.
A moon with atmosphere?
Scientists believe the organic chemical reactions taking place on Titan resemble the processes that gave rise to life on Earth 4 billion years ago. Its atmosphere is mostly nitrogen, like Earth's, but its surface temperatures of about minus 292 F make it inhospitable to life.
The saucer-shaped probe was designed to rotate on its way down, snapping the first-ever high-definition, panoramic images of Titan's thick, smoggy atmosphere and its landscape.
Along with its six scientific instruments that measure the components of Titan's atmosphere, Huygens carries a sound recorder and a lamp to look for signs of surface liquid.
Titan, believed to be the only moon in the solar system with an atmosphere, is larger than the planets Mercury and Pluto.
It is believed to have liquid methane and ethane on its surface, but the moon's heavy fog blanket makes it unclear what Huygens will encounter when it reaches its landing site.
The $3 billion Cassini-Huygens mission, a joint project of NASA and the European and Italian space agencies, was launched in 1997 from Cape Canaveral, Florida, to study Saturn, its rings, its moons and its magnetosphere.
In December, Cassini dropped off Huygens on a three-week journey toward Titan, now culminating in the probe's parachute-assisted plunge to the moon's surface.
The 705-pound probe was supposed to immediately begin transmitting data gathered by its onboard instruments and camera to Cassini.
Scientists will not know whether the instruments worked and the data was sent until Cassini turns toward Earth and begins sending the information back home.
Some science team members monitoring the flight have waited decades to see the first of 750 planned images and other scientific readings from the yellow-skied moon.
Huygens was named for the Dutch scientist who discovered Titan in 1655, NASA officials said.