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Venus Radar Request, From Earth
Decepticon
post Mar 7 2006, 02:43 AM
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I'm looking for earth based radar mapping of Venus.

I've had a hard time finding much. I clearly remember seeing images in books as a child.

Any help would be great!
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JRehling
post Mar 7 2006, 02:59 AM
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QUOTE (Decepticon @ Mar 6 2006, 06:43 PM) *
I'm looking for earth based radar mapping of Venus.

I've had a hard time finding much. I clearly remember seeing images in books as a child.

Any help would be great!


http://www.gps.caltech.edu/~margot/venus/aogbt.html

http://www.nrao.edu/pr/2001/gbtfirstsci/
(almost identical content to the first link)

http://www.nasm.si.edu/ceps/etp/venus/venusimg/P15.JPEG
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Decepticon
post Mar 7 2006, 03:25 AM
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WOW!

I didn't expect the images so clear!
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JRehling
post Mar 7 2006, 06:20 AM
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QUOTE (Decepticon @ Mar 6 2006, 07:25 PM) *
WOW!

I didn't expect the images so clear!


Compared to spacecraft flyby/orbiter standards... what terrestrial observations of Venus lack in proximity, they make up for in the size of the antennas. And those observations can be made when Venus is almost at conjunction, and thus considerably closer to the Earth than Venus or Mars ever is for a telescopic observation. Quite simply, radar observations of Venus are of considerably higher resolution than any other Earth-based observations of any planet could be.
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edstrick
post Mar 7 2006, 08:58 AM
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The only fly in this pudding is that there is a weird near-synchronicity between the rotation period of Venus and the position of inferior conjunctions with Earth. Very-Very nearly the same hemisphere of Venus faces Earth each conjunction! It's not quite exact, but it is improbably close. They've tried to see if the small tidal pull of Earth on Venus at inferior conjuction was more than vanishingly small and might explain this cooincidence, but it seems to be unlikely. The best idea I've heard so far is that the gods must be crazy.
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helvick
post Mar 7 2006, 09:46 AM
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QUOTE (edstrick @ Mar 7 2006, 08:58 AM) *
The best idea I've heard so far is that the gods must be crazy.

And are the same crazy Gods responsible for the very slow rotation of Venus? Or is there a plausible\likely explanation for it just happening that way?
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edstrick
post Mar 7 2006, 10:57 AM
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Last I heard they figure it's just coincidence.
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Decepticon
post Mar 7 2006, 01:10 PM
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The best one I've heard so far is "Venus was a Comet!" Straight from the wHoGland Funny Farm. biggrin.gif
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Jeff7
post Mar 7 2006, 08:50 PM
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Venus is made from people! Peeeoopllle!!!!!
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Guest_AlexBlackwell_*
post Mar 7 2006, 09:02 PM
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QUOTE (helvick @ Mar 7 2006, 09:46 AM) *
And are the same crazy Gods responsible for the very slow rotation of Venus? Or is there a plausible\likely explanation for it just happening that way?

Correia and Laskar have published some interesting work on this.
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Decepticon
post Mar 7 2006, 11:16 PM
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I once heard a theory that a violent impact hit Venus against it's natural spin causing it to rotate the opposite way.

What ever it was it must have been a big bugger.
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AndyG
post Mar 8 2006, 09:24 AM
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QUOTE (Decepticon @ Mar 7 2006, 11:16 PM) *
I once heard a theory that a violent impact hit Venus against it's natural spin causing it to rotate the opposite way.

What ever it was it must have been a big bugger.

Shame it didn't end up with a lovely (and life-on-Earth-supporting?) Moon like ours.

Andy
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ljk4-1
post Mar 8 2006, 02:59 PM
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QUOTE (AndyG @ Mar 8 2006, 04:24 AM) *
Shame it didn't end up with a lovely (and life-on-Earth-supporting?) Moon like ours.

Andy


I dunno - War of the Worlds could have happened coming from the
other direction.

Or in a parallel universe, it is the inhabitants of Venus who wonder
what might have been if only Earth weren't a barren wasteland.


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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JRehling
post Mar 8 2006, 04:19 PM
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QUOTE (AlexBlackwell @ Mar 7 2006, 01:02 PM) *
Correia and Laskar have published some interesting work on this.


I've tried about six of those links, and they are all dead.


QUOTE (JRehling @ Mar 8 2006, 08:10 AM) *
I've tried about six of those links, and they are all dead.


However, a summary/abstract appears here:
http://physicsweb.org/articles/news/05/6/6

The low inclination and extremely low angular momentum always made impact-based explanations unlikely. It's pretty hard to smash things together and get things to balance out that neatly. C&L's work seems to conclude that from first principles, that with an atmosphere that thick, the planet's rotation is going to be driven by the atmosphere. Presumably (what the abstract/summary doesn't say), the huge thermal input from the Sun is another part of the story. Saturn, Uranus, and Neptune have bigger atmospheres, but they don't have daysides lit by a Sun measuring a full degree in the sky -- they have two+ orders of magnitude less solar input.

I don't know if anyone has ever looked at this angle, but with Grinspoon, et al, proposing that Venus may have lacked those bright clouds for much of its history, it may have formerly had particulalry large thermal tides if it had an albedo as low as, say, Mars or Earth's continents. If you imagine an atmosphere sticking out tens of km (?) farther on the dayside than the nightside, that's a lot of friction working against rotation.
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Guest_AlexBlackwell_*
post Mar 8 2006, 04:20 PM
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QUOTE (JRehling @ Mar 8 2006, 04:10 PM) *
I've tried about six of those links, and they are all dead.

Ouch. I know it worked back in 2002; in fact, I believe I referenced it over in Yahoo! planetary_sciences at the time biggrin.gif

Try Laskar's page, though I believe these may be preprints instead of the final versions that were on Corriea's page. If you need the the final versions, John, let me know.
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