Scientists say they've found a precursor of life in an unlikely place: one of Saturn's moons.
Images from the Cassini spacecraft show plumes of water vapor, dust and ice shooting hundreds of miles out of fissures near a heated region of the moon Enceladus. The vapor spewing out near the moon's south pole is believed by scientists to contain several of the major building blocks of life, including carbon, oxygen, hydrogen and nitrogen.
"As far as I'm concerned, we just hit the ball out of the park," said Carolyn Porco, head of the Cassini imaging team and a planetary scientist at the Space Science Institute in Boulder, Colo. "This is the holy grail of modern day planetary exploration, evidence of liquid water somewhere else in the solar system."
The fissures, heat and vapor suggest that there are bodies of water, possibly just a few yards below the moon's surface, Porco said.
"These are limited small bodies of water. It's not an ocean," she said.
The area around the pole also is darkened by stripes that are hotter than the areas around them, the researchers say. The composition of the stripes suggests those areas are being churned up and reconstituted by geysers and other geological activity, the researchers say.
The researchers analyzing Cassini's data say they are mystified by it all.
"Everything seems to be happening there at the south pole and nowhere else on the surface. It's weird," said John R. Spencer, the scientist at the Southwest Research Institute who used Cassini's infrared spectrometer to measure the moon's temperatures.
Porco, Spencer and several other scientists published their findings today in the journal Science.
Enceladus is about 300 miles wide, orbits Saturn at a distance of about 147,000 miles and is covered mostly in snow and ice. The vapor it spews covers much of its bright icy surface and is believed to be a source of some of the particles that make up Saturn's rings.
But scientists didn't realize how hot and how active Enceladus was until last year when Cassini began making the first of three passes it's completed so far.
Spencer said he was intrigued when Cassini took readings from Enceladus in February 2005 that showed the moon to be warmer than expected. Subsequent passes in July and November gave researchers even clearer looks.
Spencer and others were stunned when Cassini's infrared cameras recorded Enceladus' south pole temperatures to be minus 320 degrees Fahrenheit. That was much warmer than expected.
"This is a big surprise, that there's that much heat," said Richard Greenberg, a planetary scientist at the University of Arizona who was not involved in the research.
Enceladus is one of at least two moons in the solar system believed to contain liquid water.
Europa, a moon of Jupiter, also is believed to hold a vast ocean of water, but one that lies much deeper below its surface than the reservoirs thought to be within Enceladus.
"I think this is going to generate a lot of interest in Enceladus," Greenburg said.
Launched in 1997, Cassini represents two decades of work by scientists. The project cost $3 billion and is being supervised by scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif. It is funded by NASA, the European Space Agency and the Italian Space Agency.
The bus-sized spacecraft will orbit Saturn 76 times, using five telescopes to take 300,000 images of the planet, its moons and its rings. Its instruments include one radio telescope, two infrared telescopes and a telescope that reads ultraviolet light.
But Cassini isn't scheduled to get another close look at Enceladus until its next pass in 2008. Between now and then, Cassini will continue to image plumes from the moon from a distance, and take measurements of the material emitted by its geysers, Spencer said.
Spencer said that after the Cassini mission is completed in 2008, he and other scientists hope to use it to make additional passes by Enceladus.
"Hopefully, we'll be able to get right down and look into those fissures," he said.