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Cassini spacecraft finds mysterious new aurora on Saturn
WASHINGTON, Nov 13, 2008 (Xinhua via COMTEX) --
U.S. space agency NASA reported
on Wednesday that Cassini spacecraft found Saturn has its own
unique brand of aurora that lights up the polar cap, unlike any
other planetary aurora known in the solar system.
This odd aurora revealed itself to one of the infrared
instruments on Cassini. "We've never seen an aurora like this
elsewhere," said Tom Stallard, a scientist working with Cassini
data at the University of Leicester, England. He is the lead
author of a paper that appears in the Nov. 13 issue of the journal
Nature.
"It's not just a ring of auroras like those we've seen at
Jupiter or Earth. This aurora covers an enormous area across the
pole. Our current ideas on what forms Saturn's aurora predict that
this region should be empty, so finding such a bright aurora here
is a fantastic surprise," said Stallard.
Auroras are caused by charged particles streaming along the
magnetic field lines of a planet into its atmosphere. Particles
from the sun cause Earth's auroras. Many, but not all, of the
auroras at Jupiter and Saturn are caused by particles trapped
within the magnetic environments of those planets.
Jupiter's main auroral ring, caused by interactions internal to
Jupiter's magnetic environment, is constant in size. Saturn's main
aurora, which is caused by the solar wind, changes size
dramatically as the wind varies. The newly observed aurora at
Saturn, however, doesn't fit into either category.
"Saturn's unique auroral features are telling us there is
something special and unforeseen about this planet's magnetosphere
and the way it interacts with the solar wind and the planet's
atmosphere," said Nick Achilleos, scientist at University College
London.
"Trying to explain its origin will no doubt lead us to physics
which uniquely operates in the environment of Saturn," said
Achilleos.
The new infrared aurora appears in a region hidden from NASA's
Hubble Space Telescope, which has provided views of Saturn's
ultraviolet aurora.
Cassini observed it when the spacecraft flew near Saturn's
polar region. In infrared light, the aurora sometimes fills the
region from around 82 degrees north all the way over the pole.
This new aurora is also constantly changing, even disappearing
within a 45 minute-period.
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