alan
Sep 14 2008, 02:01 AM
QUOTE
Images from instruments on Cassini as well as from telescopes on the ground reveal the presence of sporadic small-scale cloud activity in the cold late-winter north polar of Saturn's large moon Titan. These clouds lie underneath the previously discovered uniform polar cloud attributed to a quiescent ethane cloud at ~40 km and appear confined to the same latitudes as those of the largest known hydrocarbon lakes at the north pole of Titan. The physical properties of these clouds suggest that they are due to methane convection and condensation. Such convection has not been predicted for the cold winter pole, but can be caused by a process in many ways analogous to terrestrial lake-effect clouds
http://lanl.arxiv.org/abs/0809.1841also discussed on Mike Brown's page
http://www.mikebrownsplanets.com/2008/09/j...ake-effect.html
volcanopele
Sep 14 2008, 02:48 AM
What, him too?
volcanopele
Sep 14 2008, 02:51 AM
!@$!@$!@%!@%$
I just read the paper...
ngunn
Sep 14 2008, 10:22 PM
Great stuff! Mike Brown - thanks for the open publication of such interesting information. It's good to know when a piece is peer reviewed, but that's always slow and sometimes imperfect. Some at least of the reading public is ready to do it's own reviewing.
ngunn
Sep 15 2008, 10:35 AM
From the last paragraph of section 5:
On Titan, the solar insolation is so small that evaporative cooling dominates over any heating, so the lakes are never warmer than the overlying air, thus, on Titan an extra lifting mechanism - presumably mechanical lifting over topography - is required (to initiate convection).
I note there is no mention of the fact that because Titan's air can hold so much methane the mean molecular weight can decrease by 1% or more when the humidity is raised. Would this not also provide an extra lifting mechanism? Since it isn't mentioned in the paper I assume it's less significant than I thought, but I don't understand why. Can anyone enlighten me?
The final sentence is an exciting weather forecast:
With Titan's extensive north polar lakes, northern summer should be a time of dramatic northern cloud events.
In other words we ain't seen nothin yet! Let's hope we're still there watching.
ngunn
Sep 19 2008, 10:51 AM
Maybe we'll see some in the next few days - this is from Ciclops 'looking ahead':
On September 20 and 21, as Cassini approaches apoapsis, ISS will perform two observations of Titan’s trailing hemisphere. These observations will be acquired from a distance of 1.55-1.81 million km (0.97-1.12 million mi). The observations are designed to look for cloud motions over an 18-hour period, as well as to look for changes at Kraken Mare (one of the large lakes in the northern polar region).
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