How Venus died
We start assuming that Venus was a normal planet just like Earth. There are many differences however, for instance, Venus seems not to have a liquid outer core today. It is unknown if it has had one before but using the analogy with Earth we assume that it did. So let's first look at a hypothetical normal planet with mostly Earth-like features assuming Earth is the standard, not Venus.
The outer core of such a standard planet can be fluid mass, due to the high temperature. However, the inner core of a planet is solid again due to the immense pressure it is subjected to, in spite of the temperatures. In the core is a equilibrium between those two opposing tendencies.
It is spinning around the sun and spinning around its axis in a much similar way with same order of magnitude parameters. By spinning the planet behaves as a gyroscope or spinning top and can be subject to changes in spin axis direction by precession.
Just like Earth this juvenile planet Venus also has precession of the equinoxes due to a certain obliquity and the sun and (perhaps a possible moon) having a differential gravity pull on the equatorial bulge.
see also
http://www.copernican-series.com/precession.html
http://cse.ssl.berkeley.edu/lessons...th_precess.html
on precession
Other planets are also in precession, there is no moon required for that, just gravity, generally here is the math behind the idea:
http://scienceworld.wolfram.com/phy...Precession.html
Now we assume the planet to be a single unit, a single gyroscope with a single mechanical reaction. But it isn’t. The mantle and the solid inner core could be pretty much independent gyroscopes, with different characteristix, tied together by a fluid outer core.
I think we can assume from the mechanism that the sun-moon gravity force that generates the precession, is basically working on the equatorial bulge and hence on the lithosphere/mantle.
Now does the precession also work on the solid inner core? It may have an equatorial bulge. However, due to non-linear relationships, the precession logic of the inner core must differ from the mantle-crust precession. (see also Correia et al part I, 3.2) Hence the inner core has a tendency to change its spin axis in relation to the mantle crust due to dissimilar precession tendencies.
Note that the precession itself actually rotates spinning axis and hence it is changing the vector direction of the angular momentum. External forces, like gravity between celestial bodies transfer momentum this way.
The fluid outer core couples the motions of both solid systems. To keep spin axis aligned, the fluid outer core has to transmit these precession movements from mantle to the solid inner core somehow, like a torque converter in a transmission gear of a car. It contains some natural mechanic and perhaps magnetic stabilising properties to correct for that drifting motion, as we see no problems on Earth today, but its stabilising capacity is limited and can only physically control a limited angular momentum.
The size of the solid inner core is a function of amount of heat and pressure. The high temperature leads to liquefying and the high pressure leads to solidifying. But as the planet is cooling the amount of heat is decreasing and hence the solid inner core is expanding while the outer core is shrinking. The turning momentum of the inner core is of a tremendous value and the inner core grows, it’s increasing its angular momentum rapidly, to the fifth power of the radius, if I'm right
As the core grows its angular momentum increases beyond stabilization, eventually its precession drift will break alignment of the spinning axis. This causes heavy turbulence in the fluid outer core affecting the motion of the mantle and the inner core and it also generates drag and heat. The heat may have partially liquefied the solid inner core, decreasing it’s angular momentum and reversing the whole process back to stability. When the precesssion cycle is completed, realigment and stabilisation can occur again. However cooling continued and the inner core precession break out would occur again and this process may repeat over and over again until the spinning stops eventually.
Note that the growing misalignment of the spin axis causes the vector sum of the angular momentums of the mantle and the core to decrease, whilst angular momentum is transferred via external gravity forces to the infering celetial body during the precession. The actual transfer of momentum becomes visible only after the realignment, when a precession cycle is complete. There is no momentum loss, just momentum transfer over billions of years
The generated heat will be transmitted throughtout the whole planet, facilitated by the increased heat transport capability of the turbulent fluid outer core, causing the planet to melt partially or as a whole. Due to the heat convection the planets surface would be renewed by convection of material. As the heat would exceed general melting temperature it would also enough to cause limestone to decompose into calcium oxide and carbon dioxide that happens around 1100 degrees celsius. The carbon dioxide would escape from the lithosphere via the characteristic dome volcanoes (pancakes) to form a dense atmosphere. After the precession induced rotation stop, a very hot planet would remain with a dense carbon dioxide atmosphere. It would cool only very slowly as the carbon dioxide works as an isolation blanket and also retains solar heat due to greenhouse effect.
Due to interaction of the dense atmosphere with the sun stable equilibrium will emerge eventually.
Correia and Laskar (A Correia and J Laskar 2001 Nature 411 767) found that the rotation can only end in four possible spin states. Such planets can have either retrograde or 'prograde' rotation and its rotation axis may or may not have flipped during the turbulent precession braking event.
Venus has retrograde rotation now, but a flip of its rotation axis may not be likely. Most initial conditions will drive the spin of Venus towards its present state. The resulting slow spin sets a scenario for the retrograde stable motion purely from atmospheric and internal phenomena
In the mean time we have addressed all enigmatic features,
1: the rotation stop as a combination of the big precession brake and the Correia atmospheric drag mechanism
2: the resurfacing due to a tremendous heat generated by the hot brake, partially melting the planet.
3: the dense carbon dioxide atmosphere as all the carbon was forced out the lithosphere by chemical processes under the extreme heat.
4: the heat itself as residual from the disaster that seems to have ended 500 million years ago.
