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Polygons in space

05/28/2007 04:00 AM

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news

10/04/2007

Polygons in space

We may not have found other life in our Solar System, but we have, it appears,

found a polygon. An odd, six-sided, honeycomb-shaped feature circling the entire

north pole of Saturn has captured the interest of scientists with NASA's Cassini

mission.

NASA's Voyager 1 and 2 spacecraft produced

images of the hexagon over two decades

ago. The fact that it has appeared in the

recent Cassini images indicates that it is a

long-lived feature. A second hexagon,

significantly darker than the brighter

historical feature, is also visible in the

Cassini pictures. The spacecraft's visual and

infrared mapping spectrometer is the first

instrument to capture the entire hexagon

feature in one image.

"This is a very strange feature, lying in a

precise geometric fashion with six nearly

equally straight sides," said Kevin Baines,

atmospheric expert and member of Cassini's

visual and infrared mapping spectrometer

team at NASA's Jet Propulsion Laboratory.

"We've never seen anything like this on any

other planet. Indeed, Saturn's thick

atmosphere where circularly-shaped waves

and convective cells dominate is perhaps the

last place you'd expect to see such a six-

sided geometric figure, yet there it is."

This nighttime view of Saturn's north pole by the

visual and infrared mapping spectrometer

onboard

NASA's Cassini orbiter clearly shows a bizarre

six-sided hexagon feature encircling the entire

north pole. Credit: NASA/JPL/University of

Arizona

The hexagon is similar to Earth's polar vortex, which has winds blowing in a

circular pattern around the polar region. On Saturn, the vortex has a hexagonal

rather than circular shape. The hexagon is nearly 25,000 kilometers across. Nearly

four Earths could fit inside it. (You can see a movie of the rotating hexagon at

NASA .)

The new images taken in thermal-infrared light show the hexagon extends much

deeper down into the atmosphere than previously expected, some 100 kilometers

below the cloud tops. A system of clouds lies within the hexagon. The clouds

appear to be whipping around the hexagon like cars on a racetrack.

http://plus.maths.org/latestnews/jan-apr07/hexagon/index.html

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Polygons in space

05/28/2007 04:00 AM

"It's amazing to see such striking differences on opposite ends of Saturn's poles,"

said Bob Brown, team leader of the Cassini visual and infrared mapping

spectrometer. "At the south pole we have what appears to be a hurricane with a

giant eye, and at the north pole of Saturn we have this geometric feature, which is

completely different."

The Saturn north pole hexagon has not been visible to Cassini's visual cameras,

because it's winter in that area, so the hexagon is under the cover of the long

polar night, which lasts about 15 years. The infrared mapping spectrometer can

image Saturn in both daytime and nighttime conditions and see deep inside. It

used thermal wavelengths near 5 microns (seven times the wavelength of light

visible to the human eye) during a 12-day period beginning on 30 October 2006 to

create an image of the hexagon. As winter wanes over the next two years, the

hexagon may become visible to the visual cameras.

Based on the new images and more information on the depth of the feature,

scientists think it is not linked to Saturn's radio emissions or to auroral activity, as

once contemplated, even though Saturn's northern aurora lies nearly overhead.

The hexagon appears to have remained fixed with Saturn's rotation rate and axis

since first glimpsed by Voyager 26 years ago. The actual rotation rate of Saturn is

still uncertain.

"Once we understand its dynamical nature, this long-lived, deep-seated polar

hexagon may give us a clue to the true rotation rate of the deep atmosphere and

perhaps the interior," added Baines.

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http://plus.maths.org/latestnews/jan-apr07/hexagon/index.html

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Polygons in space - Saturn.pdf

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