Image: Arrow on Titan
NASA / JPL / SSI
A bright arrow-shaped storm blows across the equatorial region of Titan in this infrared image from NASA's Cassini spacecraft, chronicling the seasonal weather changes on Saturn's largest moon. The part of the storm that is visible here measures 1,200 kilometers (750 miles) in length east to west and 1,500 kilometers (930 miles) in length.
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updated 8/16/2011 5:34:44 PM ET 2011-08-16T21:34:44

The mystery of a giant arrow-shaped cloud on Titan, Saturn's largest moon, may now be solved. A new study suggests that the enigma was likely caused by a massive wave rippling through the moon's atmosphere.

The discovery could help scientists better understand similar phenomena on Earth, especially in light of changing global climate, researchers said.

NASA's Cassini spacecraft detected the cloud at Titan's equator in September 2010. The cloud is huge, with each side running about 930 miles (1,500 kilometers) long. [See the giant arrow cloud of Titan]

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To understand just how such a bizarre cloud might have formed, planetary scientist Jonathan Mitchell at the University of California at Los Angeles and his colleagues simulated the moon's atmosphere with a three-dimensional global climate model.

Titan's cloud-shaping waves
The researchers discovered that waves at Titan's equator could organize clouds into this shape. To picture how waves might do so, imagine a wineglass ringing with a pure resonant tone.

"A wineglass can only support certain types of sound waves because of how the system is structured, and the same holds true in this case on Titan," Mitchell told Space.com. "It's just the natural way the system wants to vibrate. Individual clouds might 'ring the bell,' so to speak, and once this ringing starts, the clouds have to respond to that vibration."

These extraordinary cloud patterns can result in downpours with up to 20 times the average rainfall. These could be key to shaping Titan's surface by erosion, explaining the widespread presence of certain valleys, researchers said. [Photos: Titan, Saturn's Largest Moon]

More weird Titan clouds?
Future studies can look at the entire archive of observations of Titan from Cassini "for other distinct, cool-looking clouds," Mitchell said. "The hope is that we can repeat this sort of analysis to learn even more about what shapes Titan's weather."

Such research could shed light on Earth, "since Earth and Titan are sort of like strange siblings," Mitchell said. He noted that Titan's atmosphere was much like that seen at Earth's tropical zone around its equator — "things that only happen at Earth's tropics are spread all over the globe on Titan."

"These planetary-scale waves that organize storms on Titan are much like waves seen organizing storms in Earth's tropics, although they're less obvious here," Mitchell said. "My hope is that this helps us understand Earth's weather in a changing climate."

The scientists detailed their findings online Sunday in the journal Nature Geoscience.

Follow Space.com contributor Charles Q. Choi on Twitter @cqchoi. Visit SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Video: First look at Titan

Photos: Best of Cassini

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  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
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  1. NASA / JPL / Space Science Institute
    Above: Slideshow (14) Best of Cassini
  2. Image:
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    Slideshow (12) Month in Space: January 2014

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