We’ve suspected for many years that something remarkable is going on on
Titan, and yet the evidence to nail this conjecture has been strangely
difficult to find.
The idea in question is whether Titan’s atmosphere actively shapes its
surface, as occurs on Earth. There’s no shortage of evidence that hints at a
complex, vibrant climate with rains that have carved streams and rivers into
the surface of Saturn’s largest moon, creating lakes and shorelines in the
process.
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But all this could be misleading, say Mike Brown at Caltech and a few pals.
They put it like this:
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“It is possible that the identified lake features could be filled
with ethane, an involatile, long-term residue of atmospheric photolysis; the
apparent stream and channel features could be ancient from a previous climate;
and the tropospheric methane clouds, while frequent, could cause no rain to
reach the surface.”
In this context, the importance of the discovery of fog at Titan’s south
pole cannot be underestimated (coming courtesy of images from the Cassini
spacecraft).
On Earth, fog can form in a number of ways, but most of these mechanisms
cannot work on Titan. “Fog on Titan can only be caused by evaporation of
liquid methane,” the team says. “The detection of fog provides the
first direct link between surface and atmospheric methane.”
And that’s important why? First, because it’s evidence of a hydrological
cycle in which an evaporating liquid on the surface enters the atmosphere. And
second, because it finally confirms Titan as an active meteorological body in
its own right.
