|If Santa Were a Martian
The Martian North Polar Cap
If Santa Claus were a martian, he'd be in for one bumpy ride.
That's the assessment of navigators and engineers controlling the
flight of NASA's 2001 Mars Odyssey spacecraft as it presently flies four times
daily above the north polar region of Mars.
"If he were flying above the North Pole of Mars, my advice to
Santa would be 'Hang tight onto your reins,'" said Odyssey navigator
John C. Smith. "You could be in for a rough ride."
In the midst of aerobraking
maneuvers that are lowering the
spacecraft's orbit around Mars, the Odyssey team has discovered an
unexpected and somewhat unpredictable north polar atmospheric
disturbance that is making the job a real adventure, Smith said.
Fasten Your Seatbelt
Called the "polar vortex," this cold, low density region
forms each winter in the atmosphere above the planet's latitudes
70 degrees north and higher. The region between the polar vortex and
the rest of the atmosphere is called the 'transition zone.' In this zone,
strong winds swirl around the pole and the zone itself weaves in and out
in the typical fashion of a terrestrial jet stream. It is an area where
sometimes surprising shifts in the atmospheric density can become
fasten-your-seatbelt territory for Odyssey.
"When we're in the transition zone, the atmosphere is very
unpredictable," said Smith.
Scientists and engineers have long known that Mars'
atmosphere "breathes" -- moving up and down,
growing or decreasing in density with the effects of dust storms, winds
and other influences. But scientists and navigators are just getting to
know up-close the peripatetic polar vortex and its shifty transition zone.
If Santa Were a Martian
Aerobraking: It's a Drag
"Try to Go with the Flow"