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ne of the most remarkable features of the
solar system is the variety of planetary
atmospheres. Earth and Venus are of
comparable size and mass, yet the surface of Venus
bakes at 460 degrees Celsius under an ocean
of carbon dioxide that bears down with the
weight of a kilometer of water. Callisto and Titan—planet-size
moons of Jupiter and Saturn,
respectively—are nearly the same size, yet Titan
has a nitrogen-rich atmosphere thicker than
our own, whereas Callisto is essentially airless.
What causes such extremes? If we knew, it would
help explain why Earth teems with life while its
planetary siblings appear to be dead. Knowing
how atmospheres evolve is also essential to determining
which planets beyond our solar system
might be habitable.
A planet can acquire a gaseous cloak in
感觉这个更像 |
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