Did Venus Have A Moon? Options

[nprev]

...or two?

http://skytonight.com/news/home/4353026.html

[edstrick]

Venus's solar tidal drag on the solid body is enough to have modified the planet's spin rate, but as I recall, models have indicated despinning from solid body tide during the age of the solar system is unlikely.

There are also significant thermally driven and gravitational tides in the atmosphere, some models have indicated these have contributed to the non-zero spin rate of the planet.

The really BIZARRE and unexplanable thing is that Venus is close to being tidally locked with the same hemisphere facing Earth every conjunction. It's not exact, but it is very close. No tidal model involving Earth comes anywhere near able to explain that and it may be pure cooincidence.

Note: All this info is off the top of my head from old studies. Take with a grain of iron sulfide <venusian salt>

[Rob Pinnegar]

There are also significant thermally driven and gravitational tides in the atmosphere, some models have indicated these have contributed to the non-zero spin rate of the planet.

The really BIZARRE and unexplanable thing is that Venus is close to being tidally locked with the same hemisphere facing Earth every conjunction...

I also remember these points now that you mention them. First guess: they were probably reported in an old issue of Astronomy or Sky&Tel. It would have to have been a long time ago, as my subscriptions to those magazines ran out around 1990 or thereabouts. (By then, I was at U o'Toronto and had discovered journals.)

These sorts of observational coincidences, i.e. the same side of the planet facing us at optimal observation times, led to astronomers thinking that both Mercury and Venus were locked in synchronous rotation around the Sun for a long time. (I know you know that, Ed, but am mentioning it for other readers who might not.)

As for tidal forces, keep in mind that they go by the inverse *cube* of the distance, so Venus' solar tides are about as strong as Earth's solar and lunar tides combined.