Image: Saturn's A ring
NASA / University of Colorado / LASP
A color-enhanced ultraviolet image captured by Cassini shows Saturn's A ring. The A ring begins with a "dirty" interior of red, followed by a general pattern of more turquoise as it spreads away from the planet. The blue colors indicate denser material made up of ice. The red band three-fourths of the way outward is known as the Encke Gap.
By Alan Boyle Science editor
msnbc.com
updated 7/7/2004 8:26:37 PM ET 2004-07-08T00:26:37

Saturn may be in the Cassini spacecraft's rear-view mirror, but the science team behind the international mission is continuing to take in data — including eye-opening readings of the planet's rings.

After a seven-year cruise, the bus-sized probe successfully fired its engine to enter Saturnian orbit last Wednesday night, and it's now heading away from the planet for its first full 116-day circuit.

Scientists are continuing to process data from last week's close encounters. The science team for Cassini's Ultraviolet Imaging Spectrograph, or UVIS, reported Wednesday that Saturn's rings were sparser and dirtier toward the inside, but denser and icier toward the outside.

Such findings could lead researchers to a better understanding of how the rings evolved, said Larry Esposito of the University of Colorado at Boulder, who leads the UVIS team.

Esposito sketched out two possible explanations for variations in the rings.

"One is that the different parts of the rings are fragments from different moons that had different compositions," he told MSNBC.com.

The other explanation, which he prefers, is based on the fact that "the rings are constantly bombarded by meteorites which are dark and dirty, compared with the clean ice that we'd see."

Image: C and B rings
NASA / University of Colorado / LASP
This image shows Saturn's outer C and inner B rings from left to right, with the inner B ring beginning a little more than halfway across the image. The general pattern is from "dirty" red particles to denser turquoise ice as the ringlets spread outward.

That dark material makes a big impact on the inner, sparser region of the rings. But toward the outside, where the rings are denser, the greater volume of ice "dilutes the meteorite input," Erickson said.

It's too early to determine which explanation fits the data better, he said.

"We're still working with our data to try to determine these answers ourselves," he said, by running the UVIS readings through various computer models for ring dynamics. Esposito and his colleagues are also looking forward to more observations of Saturn's rings.

Wide-angle view
As Cassini zooms away from Saturn, the scientific instruments can get a wide-angle perspective on the planet and its surroundings.

"We'll actually be making movies of Saturn as part of that," Linda Spilker, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told MSNBC.com Wednesday. "When you get a little bit farther away, that's a good time to make movies."

In Cassini's case, the "movies" are time-lapse sequences showing the dynamics of Saturn's atmosphere, its rings and its moons.

Image: Iapetus
NASA / JPL / SSI
Cassini's view of Iapetus reveals the moon's two-tone appearance. The image was captured on Saturday after the probe entered Saturn orbit. Cassini will come even closer later in the mission.
For example, earlier Cassini sequences traced the movement of storms on Jupiter as well as Saturn, and views of Saturnian moons ranging from huge Titan to tiny Atlas.

Spilker said the science team would also be observing the distribution of hydrogen and oxygen across the Saturnian system, as well as activity in the magnetosphere. On its way out from Saturn, Cassini already captured closer views of Iapetus and other moons.

"We got more hints of what Iapetus might look like," Spilker said. "I see this as a kind of teaser for what's coming up."

Mysteries of Titan
Titan — which is Saturn's largest moon as well as the only moon in the solar system with a thick atmosphere — was an important target during Cassini's first post-insertion pass on Friday, and it will be even more important this fall and winter.

Cassini is equipped with camera filters and other instruments that can pierce through Titan's obscuring smog, and even during Friday's flyby, scientists had hoped to see clear evidence that Titan possessed oceans or lakes of liquid methane and ethane.

They didn't get the readings they expected, but Spilker said that doesn't mean the liquid isn't there.

Video: Titan revealed "That's still a big question mark," Spilker said. "If there had been global oceans, we would have seen them by now, but there still could be some substantial lakes."

In addition to the question about liquid hydrocarbons, scientists are intrigued by the linear and circular features they saw in the Titan flyby imagery.

The lines could represent faults in Titan's surface, and the circles could be craters — all of which may well indicate that the icy moon is geologically active, like Jupiter's equally mysterious moon Europa.

This first round of data is only whetting Spilker's appetite for the much closer flyby of Titan on Oct. 26, when Cassini is due to come within 750 miles (1,200 kilometers) of the moon's surface.

"That will be 300 times closer than the one after Saturn orbit insertion," she said. "We know that with the camera and the Visible and Infrared Mapping Spectrometer we can see through to the surface, so we'll get just much more detail on what the surface looks like."

Yet another flyby will bring Cassini just 1,475 miles (2,360 kilometers) from Titan on Dec. 13, and on Christmas Eve, the spacecraft will send its piggyback Huygens probe toward Titan for a trip through Titan's atmosphere. Now that Saturn orbit insertion is out of the way, the release of the Huygens probe looms as the mission team's next nail-biting moment.

"We have a slight breather with this 116-day orbit," Spilker said, "but that gives us time to focus on the probe release activities."

As Cassini's four-year mission proceeds, the orbits get tighter — and the breathers get shorter.

"Once we get a couple of years into the mission, we fly by Titan every 16 days," Spilker said.

© 2013 msnbc.com Reprints

Photos: Best of Cassini

loading photos...
  1. Starring Saturn

    This backlit view of Saturn was voted the favorite image to come from the Cassini orbiter - and it has been described as "perhaps the most stunning photograph ever taken." The image, captured on Sept. 15, 2006, shows two faint rings that were discovered by the Cassini team. And at the highest resolution, Earth itself appears as a pale blue dot just to the left of the brightest rings, at about the 10 o'clock position. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  2. Dark rings

    An infrared image from the Cassini orbiter, acquired May 24, 2007, reveals clouds beneath the hazes in Saturn's atmosphere, as well as the unilluminated side of the giant planet's rings. The shadows of the rings fall upon the planet's cloud layer. This image shares the honors as the favorite black-and-white picture from Cassini. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  3. Abstract art

    A Cassini image from May 10, 2006, shows the shaded edge of Saturn's disk, rounded by dark rings seen nearly edge-on. The crescent disk of Titan, Saturn's largest moon, can be seen in the background beyond the rings. This image shares the honors as the favorite black-and-white image from Cassini. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  4. Pearly moons

    Two of Saturn's moons - Tethys and Enceladus - look like pearls backdropped by the planet's disk in this image, captured on July 24, 2007. The thin "string" connecting the pearls is actually the plane of the planet's rings, seen edge-on. The rings cast a dark shadow on Saturn's disk. Two other moons appear in this image, although they can barely be made out at the highest resolution: Hyperion is near the lower left corner of the image, and Epimetheus is the slightest of specks between Tethys and Enceladus. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  5. Saturn from on high

    The Cassini spacecraft provides a high-contrast view of Saturn and its rings, as seen from above. This portrait is actually a mosaic of 36 images taken on Jan. 19, 2007, from about 40 degrees above the plane of the rings. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  6. Shadows on clouds

    Saturn's darkened rings cast shadows on the planet's blue and gold cloud tops, while the moon Dione hangs like a dot in the black sky beyond. This image was taken by the Cassini spacecraft on Feb. 4, 2007, from a distance of about 800,000 miles. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  7. View from below

    Cassini coasts beneath giant Saturn, staring upward at its gleaming crescent and icy rings. A great bull's-eye pattern is centered on the south pole, where a vast, hurricane-like storm spins. This view, obtained on Jan. 30, 2007, looks toward the lit side of the rings from about 26 degrees below the ring plane. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  8. Pastel planet

    Dark and sharply defined ring shadows appear to constrict the flow of color from Saturn's warmly hued south to the bluish northern latitudes. Scientists studying Saturn are not yet sure about the precise cause of the color change from north to south. The different colors may be due to seasonal effects on the atmosphere. The images that went into this mosaic were obtained by the Cassini spacecraft on Feb. 4, 2007. (NASA / JPL / Space Science Institute) Back to slideshow navigation
  9. Ringing success

    This ultraviolet image from the Cassini spacecraft shows the detailed composition of Saturn's outer C and inner B rings from left to right, with the inner B ring beginning a little more than halfway across the image. The general pattern is from "dirty" red particles to the denser ice shown in turquoise as the ringlets spread outward. (University Of Colorado, LASP / AP) Back to slideshow navigation
  10. A is for amazing

    This ultraviolet image shows the A ring, beginning with a 'dirty' interior of red followed by a general pattern of more turquoise as it spreads away from the planet, indicating a denser material made up of ice. The red band roughly three-fourths of the way outward in the A ring is known as the Encke gap. (University Of Colorado, LASP - NASA / Reuters) Back to slideshow navigation
  11. Casting a shadow

    This image taken by Cassini shows the planet Saturn casting a shadow over its rings. (NASA - JPL - Caltech / Reuters) Back to slideshow navigation
  12. Titan revealed

    This is an infrared image of Titan, one of Saturn's moons, mapping the surface hidden beneath the moon's opaque atmosphere. Green areas represent water ice, while yellow areas have higher concentrations of hydrocarbons. The white spot is a methane cloud. (NASA) Back to slideshow navigation
  13. Ripples in the ring

    Scallops in the ring on the left side of this image were likely caused by a Saturnian moon rolling along the edge. One bright ringlet is visible within the gap, and at least one other faint ringlet can be made out. "This is textbook ring physics, right there, in one image," says Cassini imaging team leader Carolyn Porco. (NASA - SSI) Back to slideshow navigation
  14. Wisps in space

    A close-up of one of Saturn's rings shows a wispy pattern of ripples that may have been stirred up by a moonlet's orbit. Such unprecedented views of ring details are possible because of the Cassini camera's resolution. (NASA TV) Back to slideshow navigation
  1. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  2. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  3. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  4. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments