Explaining Venus

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Oki, i'm still onboard

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We're Here

Andre,

Just to let you know others are following your post even though no comments are being posted. It isn't from a lack of interest but to see if you have a viable scenareo.

 

I am fascinated by Venus. I feel it is a blind spot in our understanding of planetary dynamics. Why is it that it has such a dense atmosphere full of CO2? Its slow orbital rotations and tectonic features are a puzzle too. Thank you André for directing me to this thread. Let’s analyze your evidence first.
[/quote] Venus was probably rotating normally a few billion years ago, likely the spin axis a bit tilted like the Earth. Also, it has an equatorial bulge and with those properties, also a precession movement, just like Earth, the Precession of the Equinoxes. This precession is supposed to be caused by differential gravity pull of the sun and moon on the closest and farther part of the equatorial bulge.[/quote]
but Venus does not have a moon. So it cannot have precession.
[/quote] Again, it has a bigger core and if it exists, the bigger geo-nuclear reactor ..err.. Venus-nuclear reactor. This is burning much faster and therefore terminating operation much earlier than Earth.[/quote]
why should it have a bigger core? Anyway planets do not have a nuclear reactor at its core. Its heat comes not from fission or fusion like that of the sun but from natural radioactive decay. This process depends only on how much radioactive element the planets have as the rate of decay is constant. Since Venus is less massive and has lesser quantities of radioactive element than earth its heat production is lesser and will end earlier than earth irrespective of the internal structure of the planet. Since the chemical composition of earth and Venus is more or less the same one can estimate how much radioactive element it has and hence how much heat it generates. Calculations show that though less than earth Venus still produces substantial internal heat to make it geologically active. Venus is not dead, far from it.

how about the enormous drag produced by its extremely thick and massive atmosphere. I read in a book that it is enough to explain its rotational peculiarities.

I have pointed out that there can be no precession occurring in Venus as it has no satellite. Today Venus has no liquid outer core . I infer this from the fact that Venus has no magnetic field. Did it have one before? Do not know and have failed to find any literature at all on the subject. Venus has lesser mass than earth. So it cools faster and has less pressure than earth. The inner core of earth is solid in spite of the high temperature due to the immense pressure it is subjected to. In the core it is a battle between two opposing tendencies, the high temp. tries to liquefy and the high pressure tries to solidify. Where pressure is dominant(inner core) it is solid and where temperature is dominant(outer core) it is liquid. But as the earth cools the temperature decreases and hence the solid inner core expands at the cost of the outer core. Since cooling is much faster for the smaller Venus it may be that the though there was a liquid outer core at the beginning it has solidified completely long ago. This can be verified by taking rock samples and see if there is any evidence of ancient magnetism.

I do not like building castles in the air. But with so little to go on I have no choice.
1)Firstly suppose that the liquid outer core did exist and that its last remnants solidified 300-500 million years ago. the magnetic field of Venus will suddenly(?) disappear and there may be frictional drag between the faster rotating solid inner core and the slow rotating inner mantle(or is it the other way round). Huge heat generated. Gargantuan lava flows and magma oceans, complete surface refacement. All this without using RPTW, which cannot occur as Venus, has no precessional motion.
2)perhaps the liquid outer core solidified much earlier. Since we do not know the effects of the outer core on mantle convection. The solidification of outer core may switch of the convection current in the mantle. Lacking such efficient heat loss mechanism heat builds up in the interior until the time comes when the inner mantle partially liquefies, becomes lighter than the cooler outer mantle and rises up en masse again resulting in gigantic mantle plumes resulting in complete resurfacing of Venus.this happens periodically in the planet’s history, the last one happening 300-500 million years ago. Paradoxically cooling and resulting fractional distillation of the outer mantle as its lighter elements enter the crust, makes it progressively heavy making it liable to sink as lower mantle tries to rise up. The upper mantle of earth does not sink as a lighter is present in it. This is water. Venus being water poor has no such lightener making periodic massive upwelling of lower mantle inevitable(or so the theory claims).
Whatever the merits of the theory it revolves around two substantial points. There is no convection currents in the mantle of Venus for then we would have seen earth like geological activity on its surface and it generates enough heat for it to be geologically active.
3) another elegant idea is that convection cannot take place within Venus as its crust is too thick to be penetrated by the mantle. Earths oceanic crust is only 8km thick and it is nowhere more than 80km thick underneath the continents. However if all the lighter elements had risen up from the upper mantle it should have been anywhere between 300 to 500 km thick. That this is not so is due to the fact that most rocks in the crust are associated with water and due to this above certain temperature and pressure they metamorphose into much denser rocks and sink into the upper mantle. So in earth water restricts the thickness of the crust making convection possible. Venetian crust, devoid of water has become too thick for convection making heat transfer inefficient. The rest is identical to (2). Maybe 2 and 3 both act in consort.
4) finally why does venus have such a thick atmosphere full of CO2. reverse the question. WHY DOES EARTH HAS SUCH A THIN ATMOSPHERE WITH SO LITTLE CO2? Venus has a thick atmosphere and its gravity is capable of holding it in place. Earth is larger than Venus. Should we not expect that earth should have been able to capture an even denser atmosphere at the time of her formation? So what happened? We know what happened. A large planetoid about the size of mars hit earth and blasted out the moon along with her entire primeval dense atmosphere to space. Her thin atmosphere was formed later as volcanoes spewed out gases which emanated from the upper mantle and thus was of a different composition to that of the primeval atmosphere we see on Venus. Still it was rich in CO2 and oxygen poor, but the advent of life changed all that. So as far as atmospheric density and composition is concerned, Venus is the prototype and earth is the anomaly. Lucky for us though! The peculiar conditions on earth arising from a historical collision thinned the atmosphere, enabled water to persist and ultimately resulted in life.

 

I must leave my hat off to you for such a well thought-out hypothesis.

 

Why is this? The surface of Venus is in the region of 700 degrees K. The Curie Point for iron is 1043 degrees K. 300 degrees difference there...should be magnetism around if there was a magnetic field.

The reason for Venus' retrograde orbit is that it was proabably hit by a planetoid during formation. Your theory requires Venus to have more radioactive elements, which is unlikely as it has a similar density to Earth. This would mean that this would have to be compensated by adding more light elements to the planet. Does this not contradict your statment of the inner planets having more heavy elements? Or have I missed the ball completely?

TheCat

 

The effect of heat on magnetism

Perhaps we can start with a simple experiment...

"Stroke a bit of iron or steel (such as a pin or a screwdriver) across the magnet. Show how this makes a new magnet, and how the new magnet can attract other bits of steel or the iron ore. By placing the new magnet under the paper, you can show with the ore that this magnet is not as powerful as the original. Heat up the pin or screwdriver to show how heat destroys the magnetism."
http://www.scitoys.com/scitoys/scitoys/magnets/magnets.html

 

Venusian Magnetic Field

http://www.eurekalert.org/pub_releases/2001-08/ns-iem082201.php
"Earth and Venus are similar in size and basic composition, yet Earth has a field while Venus doesn't. No one knows why, but flow might be the key."
---
"Unlike the Earth, Venus's crust hasn't split into tectonic plates. This reduces the effectiveness of the planet's convection cooling system and suppresses any turbulence. Venus may also rotate too slowly to calm and organise any turbulence that does arise. Whichever is lacking, something in the flow seems to stop Venus's core generating a field. Only by building mock-ups of the Earth's core will we find out what's really going on."

Excerpts from the Eurekalert article "Is Earth's magnetic field failing?" 22-Aug-200

 

Venus' Remanent Crustal Magnetism Destroyed by Heat

I've added the boldface to the teXt below.
http://www-ssc.igpp.ucla.edu/personnel/russell/papers/venus_mag/
"While solid core formation in Earth's interior maintains its dynamo to this day by virtue of the related 'stirring' of the molten core around it, Venus appears to either lack the necessary internal ingredients (chemical or physical) for solid core formation, or to have ceased such processes at an earlier time if they resulted in complete core solidification or arrested core solidification. It is important to note that, contrary to popular belief, dynamo theory does not credit the smallness of the magnetic moment to the slow rotation of Venus (a Venus day of ~ 243 Earth days is almost equal to the length of its year of ~ 224 days, and its sense of rotation is retrograde). It is also notable that Venus would not have maintained any remanent crustal magnetic fields from its proposed early period of dynamo activity because the temperatures in the crust are expected to be above the Curie point (below which such fields could persist in rocky materials).

 

Okay, André, here is the guy to give all the answers to...

Hakan Svedhem, project scientist for European Space Agency's Venus Express, says, "The atmosphere of Venus is unique in the Solar System, so understanding it is very important."

http://www.eurekalert.org/pub_releases/2002-11/esa-nso112802.php
28-Nov-2002
"No shortage of mysteries on Venus"
Contact: Monica Talevi
monica.talevi@esa.int
31-71-565-3223
European Space Agency

Here is the Venus Express site
http://sci.esa.int/home/venusexpress/index.cfm

contact page
http://sci.esa.int/action/contact/

 

Okey-dokey, so it looks like any past magnetic field would not be recorded.

I'm far from convinced about TPW causing retrograde motion. Venus has true retrograde motion, that is, it is rotating very slowly in the oppposite direction to all other planets. I think your hypothesis (at the moment) can't really account for this, unlike the planetoid collision hypothesis...but as you say, you are just playing around with thoughts at the moment...keep us informed of your progress!

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thanks for the last thread. it shows that a thick venetian atm. can slow down and even reverse rotation.now for the reply,
[/quote] Do we really know that or is this a sophicated hypothesis based upon some evidence?[/quote]
it is a theory of course. But it is based on good evidence. Consider this.
1) mass of moon- .0123 of earth
2) mass of mercury- .055 of earth
3) mass of Pluto- .0022 of earth

moon is comparable to some of the smaller planets of the solar system. Of course some satellites of Jupiter and Saturn are larger than it, but they revolve around giants. The masses of these satellites are insignificant in comparison with that of their parent planet. But this is not the case for our earth-moon system. The only other planet to have a larger moon in comparison to its own mass is Pluto, but then it may not be a planet at all. So the earth-moon system is certainly unique in the solar system.

Now we come to the actual composition of the moon. If it formed initially as an independent planetesimal then its composition should mirror that of the ancient planetary nebulae. What is interesting is that it is singularly lacking in iron, olivine and other heavy elements. This is unexpected. What is more, moon in its entirety mirrors the composition of earth’s upper mantle. Such peculiarities can be explained on the basis of a glancing collision of a mars sized planet with primordial earth. The collision would melt the earth, destroy its early atmosphere and will eject a large amount of matter in space which would revolve round the planet and ultimately condense into our moon. It is the favoured hypothesis as it matches well with the observed facts. Of course new data can arise that will nullify the hypothesis completely. But it’s a danger that every scientific theory faces.

here are some facts-
let us denote escape velocity as V and pressure as P
1)moon:- V: 2373m/s ; P negligible
2)mercury:- V:4198m/s;P negligible(due to closeness to sun)
4) mars:- V:4953m/s; P:5mB
5) venus:- V:10359.7m/s; P:90000mB
6) earth:- V:11000m/s; p:1000mB

is it possible to establish a pattern here? I think not. There is a pressure anomaly either for earth or for venus as is clearly seen. My bet is the anomaly lies on earth caused by the impact of the planetesimal. But I may be wrong. Is there a way to calculate the expected pressure on earth, venus and mars? That should clear many ambiguities. There is a theory that mars once had a denser atmosphere which eventually dissipated in space due to its weaker gravity. More information on that is welcome.

the giants are nearly all atmosphere. What we see is the rotation of the atmosphere, nothing else. Though surface winds of venus are slow, the winds inits upper atmosphere rotates about the planet in 4 earth days only. Suppose the atmosphere of venus were so thick that we could not by any means see the planet’s rocky surface at all. Then how could we have known how sluggish its rotation actually is? We would have to infer that its rotational speed is same as its upper atmosphere that is 4 earth days. I think something like this is inferred for the gas giants. I may be wrong though. friction always dissipates energy. So though what you say may be true locally, in the long run the net kinetic energy decreases, decreasing the speed of rotation of the planet. Denser the atmosphere, more the friction and faster the slowing down.

Do not know much about precession. Is sun enough, or are satellites needed? Mars has small satellites, but are situated very close to its surface. This may be what caused its precession. Anyway how much is it compared to earth. For mercury sun is enough I think.

 

Here are some figures. R.M.S velocity of hydrogen and carbon dioxide in venus are respectively –3.025km/s and .457km/s. escape velocity of venus is 10.3597km/s.
So the escape velocity is 22 times greater than root-mean-square velocity of CO2 and only 3.5 times greater than that of hydrogen. So venetian atmosphere made up mostly of heavy gases like C02 and SO2 is quite stable even at such high temperatures.

Yet this means nothing at all. Mars is very cold and if we take the present low temperatures into consideration it will mean that mars and even moon should have had a dense atmosphere. The idea is at the time of formation the planets were much hotter than they currently are. At those high temperatures R.M.S velocities were much greater. so planets which had lesser escape velocities lost larger amount of gases and had thinner atmospheres. Thus temperature difference did not play a role in determining how much atmosphere the planets had. It was difference in gravity that mattered. Hence the stark difference in the thickness of atmosphere between earth and venus is unexpected. This difference needs an explanation. The question is how much atmosphere should an earth sized inner planet be expected to have. Should the expected atmosphere be thick like venus then we would need to explain why terrestrial atmosphere is so thin. On the other hand if the expected atmosphere be thin like earth we would need to explain why venus has such a thick atmosphere. so the key question is has any studies been carried out in order to predict the expected atmospheric pressure and composition of the planets of the inner solar system? If you know any then please post them in this thread. It only after knowing what the current models predict can we make some headway in this debate.

it is a law of physics all right, but it assumes ideal frictionless condition. In systems where frictional forces are small enough to be neglected the law holds good. In the thread you have given the scientists were concerned about short term effects in rotation due to changes in wind velocities. In such short term observations frictional forces between the thin terrestrial atmosphere and earth is negligibly small. Hence the results hold good. But in venus we are talking about the cumulative effects of frictional dissipation over periods of billions of years between the planet and its extremely dense atmosphere.(density increases frictional drag) the effects are hence substantial- so large indeed that the entire rotational kinetic energy of the planet had been dissipated away as heat due to friction. At least that is what the theory says which to me seems possible enough.
Now regarding the absence of axial tilt. Here are some interesting facts.
.

the almost circular orbit along with the absence of satellites may be why it has so little tilt. Another enigmatic fact.

I do not believe in coincidences. any ideas?

 

How often does this occur?

And viewed from earth, you couldn't tell which face is presented to earth, as the planet is shrouded in that cloud.

 

I thought perhaps because it is further away from Jupiter, so that large planet does not affect its orbit. But Mercury has a very eccentric orbit, so that thought doesn't apply.

Mercury: 88 earth days to travel around the sun. Mercury has lots of craters on its surface. (330 ft. to 620 mile diameter). Merc. has an extremely thin atmosphere, partially consisting of solar wind. Major component of its atmosphere is helium, with no oxygen, carbon dioxide or nitrogen. Mercury's day is 58.6 earth days long. The time of rotation is influenced by the tidal forces of the sun, which affect daily Mercury's body. The strongly elliptic rotation orbit is another factor.
Noon temps reach higher than 430ºC (700 Kelvin) At night, temps are lower than -180ºC (100ºK)
Source: Stars & Planets, a viewer's Guide, by Gunter D. Roth

 

Right. But where is Venus in relation to earth at those coincident times? And in between it seems the planet is rotating. I don't think we can see Venus when it is in opposition to earth, or even in conjunction(as it would be between the earth and the sun, and the sun would make it impossible to view it)...

Okay I found sage's source
http://www.nineplanets.org/venus.html
"In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach."
So when they are NOT at the closest approach we might see a different view of the planet (if we could see the surface). Yes that is a noteworthy "coincidence".... Still don't have the parameters on how often they are closest to each other...

 

Orbit and Spin

I'll work on orbit and spin, although the core is the most interesting thing...

Maybe TheCat would like to take one of the areas...

Feel free to add to, contest anything I post on this topic.
Here is a pretty good site I found on orbit of Venus in comparison to earth. Cool diagrams. Looks like a flower

http://zebu.uoregon.edu/~soper/Orbits/venusorbit.html

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Here is the path of Venus relative to the earth over 8 Earth years (which is 13 Venus years).

 

Spin & Precession

I have found Jean-Luc Margot, at Caltech, who is studying our Venus. Take a look:


"Planetary Interior Structure Revealed by Spin Dynamics
The spin state of a planet depends on external torques as well as on the distribution of mass and dissipation mechanisms within the interior. Detailed measurements of the spin dynamics can therefore provide a wealth of information about planetary interior structure and about a variety of important geophysical processes. I have been implementing a new Earth-based radar technique (Holin, 1992) that provides spin state measurements with arcsecond accuracies. The first observations were designed to determine the size and state of Mercury's core and to get a handle on dissipation processes within the interior. The existence of a molten core would place fundamental constraints on the composition and rotation state of the planet at the time of formation, while a solid core would have a significant impact on our understanding of planetary magnetic fields. Click on the image for details about the Mercury experiment. Many insights in the geophysics of Venus can be gained by long term monitoring of its spin. Seasonal variations in the rotation rate may place fundamental constraints on its climate. Venus has a large wobble which could be excited by mantle convection, volcanic or seismic activity, resurfacing, or atmospheric changes. Measurements of the precession of the spin axis of Venus (of order one arcsecond per year) will yield a direct measurement of the polar moment of inertia. This work is performed in collaboration with S.J. Peale, R.F. Jurgens, M.A. Slade, and I.V. Holin. "
http://www.gps.caltech.edu/~margot/

 

A book on Venus

http://www.uapress.arizona.edu/samples/sam1182.htm
This is a link to a book, Venus II. It lists researchers and their area of study. This can be a resource for googling on their names to find further information on Venus.