First look at icy, mysterious Titan

A space probe landed successfully on Saturn's giant moon Titan yesterday after a seven-year journey, and immediately began transmitting images of its mysterious surface. A landscape emerged of canyons carved by liquid, a possible shoreline, and ice blocks, parts of a world that scientists believe resembles the early Earth.

Titan has long been inscrutable to scientists because of its soupy, orange atmosphere. Researchers hope the images and data the Huygens probe transmits might help answer basic questions about how life formed on Earth.

''All of us continue to be amazed, as we watch the solar system unveil," said Alphonso Diaz, NASA's associate administrator of science.

The journey of the Huygens probe was particularly perilous because it had to withstand extreme temperatures, follow a precise path to succeed, and land on an unknown surface. Scientists were unsure whether the Huygens probe would strike solid ground, ice, a lake of liquid methane, or some unknown goo, though it apparently touched down on a hard surface.

Engineers and scientists choked up at mission control in Darmstadt, Germany, after a West Virginia radio telescope picked up a feeble signal from the wok-shaped Huygens as it fell slowly through Titan's atmosphere early yesterday morning. Several hours later, when they realized the machine had reached the surface and was transmitting data, the cheers and tears came.

''This is a historic event," said David Southwood, scientific program director of the European Space Agency, which built the probe. ''This data is for prosperity, it's for mankind."

Huygens, named for the Dutch astronomer who discovered Titan, detached from Cassini on Dec. 24 and plunged in a 20-day free fall toward the moon. After it hit Titan's atmosphere yesterday, the probe deployed three parachutes and recorded temperature, atmospheric conditions, wind speed, and other data during its 2-hour descent.

It was unclear how long the 9-foot probe would be able to relay data from the surface before its communication link was lost and its batteries slowly began to freeze. Jubilant scientists said the probe appeared to survive longer than 90 minutes on the surface.

''I am blown away; the darn thing worked," said David Grinspoon, a planetary scientist at the Southwest Research Institute in Colorado. ''We are not looking at a dead moon."

The landing was by far the most dramatic event of the $3.26 billion Cassini-Huygens mission, launched in 1997. After a 2-billion-mile journey, Cassini, with its Huygens hitchhiker, successfully entered Saturn's orbit last year and has already discovered new moons and beamed back breathtaking photos of Saturn's rings. The landing, the most distant ever, paves the way for a new generation of machines to visit some of the solar system's most curious planets, moons, and asteroids.

The mission is also hailed as a new era of cooperation among the world's space agencies, as missions cost more and travel farther. Thousands of scientists and engineers from 19 countries contributed to the mission, which will explore Saturn and its moons for three more years.

One of the three murky black-and-white photos released yesterday showed bright and dark regions, possibly areas crisscrossed by drainage channels and ''very suggestive of areas that have flooded or are flooded at the moment," said Martin Tomasko, a Huygens scientist. Researchers believe that liquid is probably methane or ethane.

Tomasko said he was struck by how Earthlike the landscape seemed. ''You can almost imagine yourself on the surface," he said.

Scientists have long known that Titan is too cold, at minus 290 Fahrenheit, to sustain life or have liquid water.

But it is the only moon in the solar system with a substantial atmosphere, and scientists believe its soil is filled with frozen molecules of the kind that were on Earth when life mysteriously began. The Earth has erased evidence of those years, so scientists' best hope for new insights into the origins of life may be through conditions on Titan.

Mission officials said yesterday that one of the transmitting devices on Huygens may not have been working properly, but it was too early to tell. They were not overly concerned, because Huygens was built with redundant transmitting devices.

They expect to release more images and data in the coming weeks to piece together a detailed picture of the planet.

The data ''has to be unraveled, put together," Southwood said. ''Then scientists are going to argue about what it means, as we piece together our place in the universe and how we came to be."

Beth Daley can be reached by email at bdaley@globe.com.