Both of Saturn's poles have surprising swirling hotspots
that persist even through years of polar winter, a new study reveals.
The hotspots are localized areas in Saturn's
gaseous atmosphere over its poles that are considerably warmer than the
surrounding air — they're actually about as warm as the atmosphere at Saturn's
equator, said Leigh Fletcher of the University of Oxford.
The hotspot over the southern hemisphere was
imaged by the Keck Observatories prior to arrival of the Cassini spacecraft, but the northern
hemisphere has faced away from Earth for over a decade, so its hotspot was revealed
only this year by Cassini.
Scientists had thought that solar irradiation
might be generating the hotspot in the southern hemisphere (currently in its
summer phase, facing the sun), but the existence of a similar hotspot in the
northern hemisphere, which has been plunged in wintry darkness for many years,
suggests that isn't the case.
Instead, dynamic processes in Saturn's
atmosphere may create the hotspots, the new findings, detailed in the Jan. 4
issue of the journal Science, suggest, Fletcher says.
Air being sucked downward at the poles may cause
the hotspots, while air moving upward in the atmosphere may be creating a cold
"collar" around the hotspots. These air movements could be
responsible for the raging hurricane-like storm
imaged over the south pole in 2006.
As unusual as the hotspots themselves is the
warm hexagonal ring of air surrounding the cold collar of the northern
hemisphere hotspot. Stranger still is the lack of such a shape around the south
pole.
"The mystery is... why on earth — or why on
Saturn even — do we see a hexagon around the north pole, and not around the south
pole?" Fletcher told SPACE.com.
Other missions have provided hints that Jupiter
and Neptune have hotspots over their poles as well, suggesting they could be a
feature of the atmospheres of all gaseous planets — even extrasolar
planets, Fletcher said.
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