Cassini testing for water on one of Saturn's moons

Cassini testing for water on one of Saturn's moons

Three years after gigantic geysers were spied on an icy Saturn moon, the international Cassini spacecraft is poised to plunge through the fringes of the mysterious plumes to learn how they formed.

An unmanned probe will sweep through geysers on one of Saturn's moons to measure the chemical makeup.

Wednesday's flyby will take Cassini within 30 miles of the surface of Enceladus at closest approach.
The unmanned probe will be about 120 miles above the moon as it sweeps through the edge of the geysers and measures their chemical makeup.
The carefully orchestrated event will take Cassini "deeper than we've been before," mission scientist Carolyn Porco of the Space Science Institute said in an e-mail.
Scientists long believed Enceladus, the shiniest object in the solar system, was cold and still because it resides hundreds of millions of miles from the sun. But recent evidence shows the Arizona-size satellite is geologically active, with a significant atmosphere and a relatively warm south pole.
In 2005, Cassini surprised scientists when it snapped images of geyser-like eruptions of ice particles and water vapor spewing from the south pole. The dramatic images effectively put Enceladus (en-SELL'-uh-duhs) on the short list of places within the solar system most likely to have conditions suitable for extraterrestrial life.
Scientists generally agree the presence of water, organic compounds and a stable heat source are needed to support primitive life.
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Previous measurements by Cassini showed the eruptions were frequent, with gases and particles venting from the surface at about 800 mph and forming plumes hundreds of miles high.
The source of the geysers is a mystery, but some theorize reservoirs of liquid water below the surface are likely supplying the ice and vapor seen in the plumes.
Until now, scientists have not been able to measure the plumes' makeup in detail. Using its particle analyzers, Cassini will calculate the density, size and speed of the various gases and particles. The spacecraft's cameras will also image the moon during the flyby.
Of particular interest is whether the plumes contain ammonia, which can keep water in liquid form and would bolster the theory that liquid water lies beneath.
"There's not much for us ... to do regarding the upcoming flyby except to hold our breaths and cross our fingers," John Spencer of the Southwest Research Institute in Boulder, Colorado, wrote on the Cassini blog.
The close encounter poses little danger to Cassini because the plume particles are small compared with the dust-size debris the spacecraft is used to flying through while orbiting Saturn, scientists said.
The Cassini mission is a collaboration between NASA and the European and Italian space agencies.

Endeavour crew set to lift off, assemble robot

Endeavour crew set to lift off, assemble robot

Astronauts bound for orbit this week will dabble in science fiction, assembling a "monstrous" two-armed space station robot that will rise like Frankenstein from its transport bed.

Endeavour commander Dominic Gorie, left, and pilot Gregory Johnson will help assemble a space robot.

Putting together Dextre, the robot, will be one of the main jobs for the seven Endeavour astronauts, who are scheduled to blast off in the wee hours of Tuesday, less than three weeks after the last shuttle flight.
They're also delivering the first piece of Japan's massive Kibo space station lab, a float-in closet for storing tools, experiments and spare parts. For the first time, each of the five major international space station partners will own a piece of the real estate.
At 16 days, the mission will be NASA's longest space station trip ever and will include five spacewalks, the most ever performed while a shuttle is docked there. Three of those spacewalks will feature Dextre, which is sure to steal the show.
With 11-foot arms, a shoulder span of nearly 8 feet and a height of 12 feet, the Canadian Space Agency's Dextre -- short for dexterous and pronounced like Dexter -- is more than a little intimidating, at least for astronaut Garrett Reisman.
"Now I wouldn't go as far to say that we're worried it's going to go run amok and take over the space station or turn evil or anything because we all know how it's operated and it doesn't have a lot of its own intelligence," Reisman told The Associated Press last week.
"But I'll tell you something ... He's enormous and to see him with his giant arms, it is a little scary. It's a little monstrous, it is."
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Dextre will be flying up aboard Endeavour in pieces, and it will be up to a team of spacewalking astronauts to assemble the 3,400-pound robot and attach it to the outside of the space station. That job will fall to Reisman, Michael Foreman and Richard Linnehan.
"I feel kind of like dad on Christmas Eve, you know, opening up this present and trying to put it together for the son or daughter and going, 'Whoa, what have I gotten myself into here with this 'some assembly required' part of the space station," Foreman said.
Reisman, who will be moving into the space station, can't wait to see Dextre rise from its shuttle transport pallet, rotating up "almost like it's Frankenstein's monster coming alive."
In reality, there's nothing sinister about Dextre. The robot, in fact, was once in the running to be the Hubble Space Telescope's savior.
Following the 2003 Columbia disaster, NASA canceled the last remaining Hubble repair mission by shuttle astronauts because of safety concerns, and considered sending Dextre up to do the job. The shuttle flight was restored after a change at NASA's helm -- it's scheduled for late summer -- and Dextre went back to being a space station assistant.
Dextre -- which cost more than $200 million -- was created by the same Canadian team that built the space shuttle and space station robot arms.
Equipped with a tool holster, Dextre is designed to assist spacewalking astronauts and, ultimately, to take over some of their dangerous outdoor work.
Dextre can pivot at the waist, and has seven joints per arm. Its hands, or grippers, have built-in socket wrenches, cameras and lights. Only one arm is designed to move at a time to keep the robot stable and avoid a two-arm collision. The robot has no face or legs, and with its long arms certainly doesn't look human.
Space station astronauts will be able to control Dextre, as will flight controllers on the ground. The robot will be attached at times to the end of the space station arm, and also be able to ride by itself along the space station arm's railway.
Canadian officials said they're convinced Dextre could have pulled off the Hubble repair job, and should have no problems replacing old batteries and other space station parts.
"It's quite surprising what a robot like Dextre can do with its sense of touch and its precision," said Daniel Rey, a Canadian Space Agency engineer who heads the project.
Dextre has only three tools, for now, versus the more than 100 tools available to spacewalking astronauts, Rey said. It will probably take months to learn how to properly use the robot; its first real job could come next year.
Linnehan, who worked on Hubble in 2002, wonders just how much Dextre will be able to do.
Even though it's suited for space station maintenance, astronauts are faster, Linnehan said. As for Hubble, he said Dextre cannot compare to a human repairman because it lacks fine motor control, and cannot think and react to problems that might crop up.
That said, Linnehan acknowledges it's "a cool project" that reminds him of Japanese animation shows from decades past, namely Gigantor the space-age robot. NASA officials agree that a big part of Dextre is learning how robots operate in space, for future exploration.
Dextre, by the way, isn't necessarily a "he."
"I tend to use 'he' because I think Dextre is a masculine name," Rey said. "But it's a robot. It's tele-operated. It doesn't have artificial intelligence yet. So I need to be more careful when I say 'he.' "