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Venera Images, VENERA 13 fully calibrated image
tasp
post Jan 10 2006, 06:30 PM
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{ I hope I phrase this well enough }

Does any one know the cooling rate for 'earth type' basaltic magma from the time of contact with liquid water to the point it has solidified as compared to the expected cooling rate for the Venusian equivalent of basaltic magma from the time of contact with the Venusian atmosphere to the point of solidification?

Is 1300 psi (or whatever it works out to) CO2 more heat absorbing than H2O at 15 psi ?

Funny if the magma on Venus solidifies faster than the magma on earth in contact with sea water.

Would this effect the forms of the rocks we expect to see?
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JRehling
post Jan 10 2006, 06:50 PM
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QUOTE (tasp @ Jan 10 2006, 10:30 AM)
{ I hope I phrase this well enough }

Does any one know the cooling rate for 'earth type' basaltic magma from the time of contact with liquid water to the point it has solidified as compared to the expected cooling rate for the Venusian equivalent of basaltic magma from the time of contact with the Venusian atmosphere to the point of solidification?

Is 1300 psi (or whatever it works out to) CO2 more heat absorbing than H2O at 15 psi ?

Funny if the magma on Venus solidifies faster than the magma on earth in contact with sea water.

Would this effect the forms of the rocks we expect to see?
*


Sea water on Earth is only at 15 psi at the shoreline (eg, on a beach). The pressure is much higher in locations of typical seafloor magma exposure, and would certainly have a much higher thermal inertia than Venus's CO2. It's also much cooler, which is another factor in the speed of heat propagation.

Water, even at 15 psi, is roughly 1000 times as dense as Earth air. Sea water is even denser. Venus's surface atmosphere is very roughly (no time for math now!) 75 times as dense as Earth air.

Anyone who has stood in a 10 km/h breeze and has also been hit by a 10 km/h ocean wave will appreciate the vast difference. Venus's atmosphere is in the middle.
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RNeuhaus
post Jan 10 2006, 07:30 PM
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QUOTE (RNeuhaus @ Jan 10 2006, 11:57 AM)
Why such strange physics laws? 

Venus has very small Tilt of axis (degrees 177.36), so Venus has no typical summer and winter and the temperature in Equatorial line must be warmer all round year and the poles which are not zenith and receive less solar energy and consequently must be cooler but the greenhouse effect might alter these physics laws. 

Why is warmer at its poles than its equator and also of nights versus days?
It would be very good that you find the link about the above odd behavior.

Rodolfo
*

I found an article which mentions about the temperature of day and night and also of polars: The polar temperature is compensated by the thermal regime of Venus in spite of the fact of the temperatures inhomogenitis between equator and poles that arise from the differential insolation. On the other hand, the night-side temperatures exceed day-side temperatures according to the authors. The thermal asymmetry of Venus was confirmed by data from infrarred radiometry on Venera 9 and Venera 10 orbiters, and in particular from the analysis of limb darkening. The variation of temperature between day and night is due mainly to a change in height of the emissivity layer in the vicinity of upper cloud deck (65-68 km).

Interesting smile.gif

More detail, click here

Rodolfo
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tedstryk
post Jan 11 2006, 02:49 PM
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Here are two more shots. An improved horizon pan:



And an improved version of that cool looking rock formation.



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paxdan
post Jan 11 2006, 04:02 PM
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Looks to me that if you flipped the rock over it matches with the surface immediately above it
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tedstryk
post Jan 11 2006, 04:35 PM
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QUOTE (paxdan @ Jan 11 2006, 04:02 PM)
Looks to me that if you flipped the rock over it matches with the surface immediately above it
*


The only problem is that in the full pan, there are many spots that look like the area above the formation with no rock sitting next to them.


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Michael Capobian...
post Jan 11 2006, 05:00 PM
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Does anyone else remember the "fact" that refraction in the dense Venusian atmosphere would be so strong that you could see the back of your own head? I remember puzzling over that for hours as a kid, but I never really believed it.

Michael


QUOTE (JRehling @ Jan 10 2006, 01:50 PM)
Sea water on Earth is only at 15 psi at the shoreline (eg, on a beach). The pressure is much higher in locations of typical seafloor magma exposure, and would certainly have a much higher thermal inertia than Venus's CO2. It's also much cooler, which is another factor in the speed of heat propagation.

Water, even at 15 psi, is roughly 1000 times as dense as Earth air. Sea water is even denser. Venus's surface atmosphere is very roughly (no time for math now!) 75 times as dense as Earth air.

Anyone who has stood in a 10 km/h breeze and has also been hit by a 10 km/h ocean wave will appreciate the vast difference. Venus's atmosphere is in the middle.
*
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Toma B
post Jan 11 2006, 05:13 PM
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I heard about refraction in Venusian atmosphere...something like "you would have feeling that you are walkin at the bottom of crater with very steep walls even if you are on flat ground...don't remember quite well about that but, seeing the back of your own head????I HAVE NEVER HEARD SOMETHING LIKE THAT...please explain...


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tedstryk
post Jan 11 2006, 05:41 PM
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QUOTE (Toma B @ Jan 11 2006, 05:13 PM)
I heard about refraction in Venusian atmosphere...something like "you would have feeling that you are walkin at the bottom of crater with very steep walls even if you are on flat ground...don't remember quite well about that but, seeing the back of your own head????I HAVE NEVER HEARD SOMETHING LIKE THAT...please explain...
*



That was an old theory, but turned out not to be the case. The Veneras showed the horizon just where it should be, when corrected for their odd imaging system.


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helvick
post Jan 11 2006, 06:43 PM
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QUOTE (Toma B @ Jan 11 2006, 06:13 PM)
I heard about refraction in Venusian atmosphere...something like "you would have feeling that you are walkin at the bottom of crater with very steep walls even if you are on flat ground.
*

I seriously doubt that.

For starters refraction effects happen at interfaces or across density gradients. For the sort of effects described here you would need to have really bizarre density gradients all around you.

Things would probably look a bit different and heat shimmer effects might be more pronounced than on earth but they would be far less extreme than under water on earth for example.

The refractive index of CO2 at STP is 1.000449 (air is 1.000292). The refractive index of a gas changes (very approximately) with density according to (RIx=1+(RIstp-1)*(Dx/Dstp) so the RI of the venusian surface atmosphere is somewhere around 1.04041 (since the Venusian surface atmospheric density is approximately 90x the density of CO2 at STP).

Snells law gives us something to calculate what this would mean for a human in a spacesuit on the surface of Venus. Assuming we have an optically neutral window and we simplify the calculation down to an air (at stp) CO2 (at Venus surface) boundary.
Snell's law : RIi*Sin(Thetai)=RIr*Sin(Thetar)
Thetai = Incident beam angle and Thetar= Refracted beam angle
So Sin(Thetar)=1.000292*(sin(45deg)/1.04041
The refracted beam would be at 42.8deg. Noticable but not significant.
As a comparison for a water:air interface on earth the equivalent refracted beam would be at 32.9deg.

All in all it might be hard to play pool well on the surface of Venus but it certainly wouldn't create any bizarre visual effects.
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JRehling
post Jan 11 2006, 07:06 PM
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QUOTE (helvick @ Jan 11 2006, 10:43 AM)
All in all it might be hard to play pool well on the surface of Venus but it certainly wouldn't create any bizarre visual effects.
*


Unless you count two scorched and imploded skeletons slumped over an incinerated pool table as a bizarre visual effect.
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ljk4-1
post Jan 11 2006, 07:20 PM
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Don Dixon made some paintings of the alleged super refraction of Venus' atmosphere from the surface here:

http://www.cosmographica.com/gallery/portf...fraction%20.htm

http://www.cosmographica.com/gallery/portf...097-Inferno.htm

As a bonus, here is Dixon's rendition of what the Pioneer Venus Day Probe probably looked like as it sat on the planet's surface and radioed back to Earth for 67 minutes in 1978:

http://www.cosmographica.com/gallery/portf...enusLanding.htm


--------------------
"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."

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Toma B
post Jan 11 2006, 07:27 PM
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QUOTE (ljk4-1 @ Jan 11 2006, 10:20 PM)
Don Dixon made some paintings of the alleged super refraction of Venus' atmosphere from the surface here:
*

...but now we know that's not true don't we? sad.gif
ljk thank you for that links....those images really rock!!!


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My "Astrophotos" gallery on flickr...
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ljk4-1
post Jan 11 2006, 07:29 PM
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QUOTE (Toma B @ Jan 11 2006, 02:27 PM)
...but now we know that's not true don't we? sad.gif
*


Yes, if you will note from his headers, the paintings were made in the 1968 to 1974 period, and Dixon even labels one as outdated.

I just thought since super refraction was being talked about here, some folks might enjoy seeing a Venus that never was. smile.gif


--------------------
"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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Guest_BruceMoomaw_*
post Jan 12 2006, 01:47 AM
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Yes, the first shots of Venus from Venera 9 and 10 turned out to be remarkable for their sheer ordinariness. Not only was there no super-refractive "swimming pool effect" (which had recently become a staple of SF stories about the planet; John Varley's first published story used it and was called "In the Bowl"), but even in those grainy photos it was clear that the horizon was fairly sharp and that the shadows even of small pebbles, despite the dense atmosphere, were quite sharp. In fact, the Soviets had equipped the two landers with floodlights on the assumption that the solar illumination might be too dim to see the surface otherwise! The much better photos from Venera 13 and 14, of course, confirmed all this even more dramatically (and also revealed that fiery orange sky, although I don't know whether that color was predicted in advance).

Scientists have, really, a pretty bad track record when it comes to predicting the optical qualities of surface photos. Remember how astonished everyone was when Viking 1's first black-and-white photos showed a light-colored sky (which later turned out to be pink) instead of the deep violet sky everyone had expected? They even predicted that deep violet sky again for Pathfinder, since there was less dust in the air at the time of its landing.
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