| Aurora
Australis | 
This
image of the southern lights, or aurora australis, was
taken in October 2001 by an Expedition Three crewmember. | | Related
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Expedition
Six
Space Chronicles #1
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By:
ISS Science Officer Don Pettit
Observing
the Atmosphere
The atmosphere
on edge presents a striking sight. You see many distinct layers
all a different shade of iridescent blue. Through binoculars, I
have counted six. I find it odd that a steady continuum of gas that
decreases its density in a predictable manner displays such distinct
visual layering. Below the blue you see an orange-red layer with
cloud tops from rising thunderheads. These thunderheads are poking
their noses up into the outer reaches of the meteoric zone where
weather as we know it ends and the stratosphere begins. These cloud
tops are at about 10 km (35,000 feet). If I use this for a ruler,
to the eye, the "blue layers" are about 3 to 4 times this thickness.
The visible part of the atmosphere then, including the lower meteoric
zone, is 4 to 5 of these rulers or 40 to 50 km thick. The outer
most blue layer quickly fades from a narrow fuzzy zone into blackness.
The most amazing aspect of this view is how thin this life-preserving
blanket is when compared to the full extent of the planet. Like
an orbital eggshell, our atmosphere looks so frail that it might
crack and be gone in an instant rendering Earthas barren and lifeless
as any other baked hunk of rock orbiting the sun.
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