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Messenger Venus flyby images
4throck
post Jun 3 2015, 09:56 AM
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QUOTE (ZLD @ Jun 2 2015, 09:43 PM) *
Not intending to be stuck on this but I do find the prominence of the lines interesting. I've never seen any other images of Venus with similarly sharp features present, beyond radar data.


There are frequent "linear" cloud features on Venus. Specially visible around the polar regions.
As far as I know, atmospheric studies (including ground based) only determined a recurrent Y shaped cloud pattern, and a ~4 days rotation period.
No other permanent features were noted. And since Venus rotates slowly, any localized persistent phenomena would be noticed.

On the IR the surface emits (heat) so you can measure that (with some degree of blocking from the clouds). But essentially you get topography/surface temperature, not albedo.

Here's an interesting link:
https://astro.uni-bonn.de/~dfischer/venus/


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Phil Stooke
post Jun 3 2015, 02:14 PM
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If you like those linear features, you'll love these! Venus by Percival Lowell, 1896:

http://www.skyandtelescope.com/wp-content/...ds/spokes_l.jpg

Phil


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JohnVV
post Jun 3 2015, 09:24 PM
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the lack of details in the "Human visible" and the over all unidirectional flow in the UV

is the reason i use a 100% synthetic ( fractal based ) cloud map for Venus
the Pioneer Venus images in PDS
http://pds-atmospheres.nmsu.edu/Venus/venus.html
and on
http://www.astrosurf.com/nunes/explor/explor_pvenus.htm
are great ,-- but rather OLD
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ZLD
post Jun 3 2015, 10:17 PM
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QUOTE (Phil Stooke @ Jun 3 2015, 09:14 AM) *
If you like those linear features, you'll love these!


By golly, Lowell has been redeemed! I see those lines exactly! laugh.gif


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JRehling
post Jun 4 2015, 05:02 PM
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I suspect that with the right filters, some details on Venus would be visible to a human observer appropriately located, but a human looking at Venus from nearby with no filters at all would be on the verge of pain from the intense brightness. I suppose you could simulate it by using a mirror to reflect sunlight onto something white on a bright, sunny day so that there was a spot with double sunlight. It's bad enough looking at snow on a sunny day, and Venus sunlit clouds are about twice as bright.

But, there is contrast at the violet end of the spectrum, just barely in the visible range, and so a person with the right "sunglasses" could see detail. But without those, the SNR would be problematic due to the greater luminance in the rest of the spectrum. And, as I mentioned above, it would be somewhere between blinding and painful.

It might be interesting to consider what polarizing filters could achieve. When I'm wearing sunglasses, I often see sun dogs in the sky and notice that without the shades, the sun dog is essentially invisible.
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4throck
post Jun 4 2015, 05:31 PM
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Lowell was too creative on his drawings and interpretations.
On that illustration he was seeing the Y shaped pattern, and that is real.
But he interpreted the shadings as linear features, and put those into the sketch.
As always, one should never over interpret low SN data :-)


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