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Saturn orbiter fights for science to the end

JPL Mission Control
Cassini project manager Earl Maize hugs Julie Webster, spacecraft operations team manager, at Mission Control at NASA’s Jet Propulsion Laboratory just after the mission’s end. Program scientist Linda Spilker is at left, and Jim Green, the head of NASA’s Planetary Science Division, is at right. (NASA Photo / Joel Kowsky)

Before its destruction, the bus-sized Cassini spacecraft fought Saturn’s buffeting atmosphere to send back scientific data for even longer than NASA thought it would.

But the end was inevitable: Twenty years after its launch, and 13 years after its arrival at the ringed planet, the final signals from Cassini were received at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., at 4:55:46 a.m. PT today.

“I’m going to call this the end of mission,” Cassini project manager Earl Maize declared, during an early-morning webcast that was watched by tens of thousands. “Project manager, off the net.”

The end was pre-ordained days earlier, when a final maneuver put the spacecraft on a course to dive into Saturn’s upper atmosphere. NASA meticulously planned out the controlled descent to make sure there was no chance that Cassini could crash into one of Saturn’s moons, which are certain to be targets for future missions.

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Cassini takes its parting shots at Saturn

Saturn view
Saturn and its rings star in one of the last raw images sent back by the Cassini orbiter. (NASA / JPL-Caltech / Space Science Institute)

The final pictures from NASA’s 13-year-long Cassini mission at Saturn are flowing in – and they’re good to the last drop.

Or even better, good to the last moonset.

Raw images, captured by Cassini’s cameras during the run-up to the bus-sized spacecraft’s scheduled destruction on Sept. 15, have been popping up by the dozens on NASA’s mission website.

Among the still-image sequences are pictures showing Enceladus, an ice-covered moon that could conceivably harbor life, as it sets on the Saturnian horizon.

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Saturn probe will go out in a blaze of science

Cassini orbiter
An artist’s conception shows the Cassini orbiter zooming through the upper layers of Saturn’s atmosphere, heading for a fiery breakup. (NASA / JPL-Caltech Illustration)

Twenty years after its launch to Saturn, NASA has set the Cassini orbiter on a course for certain destruction on Sept. 15 – but there’s a decidedly positive spin to the $3.3 billion mission’s end.

“We’ll be saddened, there’s no doubt about it, at the loss of such an incredible machine,” Cassini program manager Earl Maize said Sept. 13 during a news briefing at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “But I think all of us are going to have a great sense of pride in .. a little bit corny, perhaps … a ‘mission accomplished.’”

The bus-sized, plutonium-powered spacecraft was launched in 1997 and reached Saturn seven years later. It’s logged 4.9 billion miles, sent back nearly half a million images of the ringed planet and its moons, and transmitted 635 gigabytes worth of scientific data so far.

It’ll continue sending data all the way to the end, when it’s expected to break apart and burn up in the upper levels of Saturn’s atmosphere.

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Listen to the sound of silence in Saturn orbit

Saturn and rings
The hexagon-shaped cloud system at Saturn’s north polar region looms in the foreground with the planet’s rings stretching across the background, in an image captured by the Cassini spacecraft’s camera on April 26. Click on the image for a larger version. (NASA / JPL-Caltech / Kevin M. Gill Image / CC-BY-2.0)

The researchers behind NASA’s Cassini mission to Saturn are relieved, and a bit mystified, to discover that the narrow gap between the giant planet and its rings is virtually devoid of stray particles.

The discovery comes from the bus-sized Cassini spacecraft’s first dive through the gap on April 26, which marked the beginning of the end for the 20-year mission.

“The region between the rings and Saturn is ‘The Big Empty,’ apparently,” Cassini project manager Earl Maize of NASA’s Jet Propulsion Laboratory said in a news release.

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Cassini probe survives dive inside Saturn rings

Saturn view from Cassini
This unprocessed image of Saturn’s atmosphere was captured by the Cassini probe during its dive inside the planet’s rings. (NASA / JPL-Caltech / Space Science Institute Image)

NASA’s Cassini orbiter zoomed inside Saturn’s rings overnight for the first time in its 20-year-long flight – and lived to tell about it.

Signals received by the Deep Space Network’s Goldstone radio antenna in California confirmed that the bus-sized spacecraft survived its closest-ever encounter with the ringed planet.

Cassini zoomed as close as 1,900 miles to Saturn’s cloud tops and within about 200 miles of the innermost visible edge of the rings, at a relative speed of 77,000 mph, NASA reported in an update early today.

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Hubble sees more signs of Europa’s water

Europa plumes
These composite images show a suspected plume of material erupting two years apart from the same location on Jupiter’s icy moon Europa. Both plumes, photographed in ultraviolet light by Hubble, were seen in silhouette as the moon passed in front of Jupiter. (NASA / ESA / STScI / USGS)

Scientists say Europa, a mysterious moon of Jupiter, has shown fresh signs of watery plumes that may hint at a habitable environment beneath the ice.

Last year, the Hubble Space Telescope picked up observations of what appeared to be a plume of watery material, emanating from the same area where a plume was spotted in 2014.

The most recent plume rises about 62 miles (100 kilometers) above Europa’s surface, which is twice as high as the earlier plume.

The source of the activity is an unusually warm region of ice that appears to be crisscrossed by cracks, based on pictures captured in the late 1990s by NASA’s Galileo spacecraft.

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Enceladus shows signs of hydrothermal vents

Enceladus' plumes
This composite image shows how plumes of water emanate from fissures in the surface ice of Enceladus, one of Saturn’s moons. (NASA / JPL Illustration)

Scientists have detected molecules of hydrogen in plumes of watery material erupting from cracks in the ice of Enceladus, a moon of Saturn – and that suggests an ocean beneath the ice has hydrothermal vents that just might be capable of sustaining life.

The findings, based on an analysis of data from the Cassini orbiter, are the subject of a study published today in Science as well as a NASA news briefing.

“We’ve always wondered, ‘Are we alone in the universe?’” Linda Spilker, project scientist for the Cassini mission at NASA’s Jet Propulsion Laboratory, told GeekWire. “Now, as we look out from our own planet, we find worlds in our own solar system that might have life.”

The direct evidence is still wanting, however. The research team, headed by the Southwest Research Institute’s Hunter Waite and Christopher Glein, made their conclusions based on a chain of evidence that started with observations from Cassini’s Ion Neutral Mass Spectrometer.

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UFO? No, it’s Pan, a weird moon of Saturn

Pan
A picture taken by the high-resolution camera on the Cassini orbiter shows Pan’s weird-looking equatorial ridge. (NASA / JPL-Caltech / SSI)

Astronomers have long known that Pan, one of the “shepherd moons” in Saturn’s rings, had a weird shape. But it took this week’s high-resolution images from the Cassini orbiter to show them just how weird.

Cassini got its closest look ever at Pan on March 7, when it came within a little more than 15,000 miles of the 20-mile-wide moon. In the close-ups released on March 9, the thing looks like a flattened flying saucer, complete with a bulging ridge around the edge.

Overnight, the views sparked rounds of hilarity and awe on Twitter. Was it a cosmic turtle shell? Walnut? Ravioli? And what’s behind that strange, strange shape?

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