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, according to Xinhua.
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.