Byork wrote:Venus is tidally bound to the Earth - a condition which was first observed with radar transmission from terrestrial radio telescopes. As a result, a hemisphere of Venus faces the Earth every time the two planets come close together over a number of years.
Venus is not tidally locked to the Earth. It has very close to a 5:1 resonance between its day and the period over which it comes closest to the Earth (584 days), so we see
almost, but not quite, the same hemisphere each inferior conjunction. It is not known if the observed near-resonance is a coincidence or is driven by some sort of gravitational locking mechanism. I think the general view is that there is no Earth-Venus tidal resonance.
Initially, Venus probably revolved about its axis in the same direction as the other terrestrial planets. However, over eons of gravitational attraction to the Earth, Venus developed a retrograde rotation about the axis.
That is certainly not true- the forces are too small and the time too short. There are different ideas about how Venus developed its slow, retrograde rotation. The most likely involve some sort of solar tidal locking, or collisions early in the history of the Solar System.
Development of the retrograde axial rotation would also explain the absence of a Venusian magnetic field comparable to the Earth.
No, it doesn't. Venus is rotating fast enough that it would produce a large magnetic field if its core dynamics were the same as Earth's. The lack of a magnetic field is presumed to be the result of a lack of internal convection, or the lack of any solid core, or the lack of any liquid core.
[quote="Byork"]Venus is tidally bound to the Earth - a condition which was first observed with radar transmission from terrestrial radio telescopes. As a result, a hemisphere of Venus faces the Earth every time the two planets come close together over a number of years.[/quote]
Venus is not tidally locked to the Earth. It has very close to a 5:1 resonance between its day and the period over which it comes closest to the Earth (584 days), so we see [i]almost[/i], but not quite, the same hemisphere each inferior conjunction. It is not known if the observed near-resonance is a coincidence or is driven by some sort of gravitational locking mechanism. I think the general view is that there is no Earth-Venus tidal resonance.
[quote]Initially, Venus probably revolved about its axis in the same direction as the other terrestrial planets. However, over eons of gravitational attraction to the Earth, Venus developed a retrograde rotation about the axis.[/quote]
That is certainly not true- the forces are too small and the time too short. There are different ideas about how Venus developed its slow, retrograde rotation. The most likely involve some sort of solar tidal locking, or collisions early in the history of the Solar System.
[quote]Development of the retrograde axial rotation would also explain the absence of a Venusian magnetic field comparable to the Earth.[/quote]
No, it doesn't. Venus is rotating fast enough that it would produce a large magnetic field if its core dynamics were the same as Earth's. The lack of a magnetic field is presumed to be the result of a lack of internal convection, or the lack of any solid core, or the lack of any liquid core.