Did Venus Have A Moon? Options

[nprev]

...or two?

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

[dvandorn]

Here's a question:

If this model is correct and Venus originally had a moon that escaped -- what happened to it?

I don't suppose it's possible that this original Venusian moon that escaped is now called Mercury?

-the other Doug

[Rob Pinnegar]

I don't suppose it's possible that this original Venusian moon that escaped is now called Mercury?

That's a nice idea -- but it would run into the same problems that plagued the "coaccretion" hypothesis for the formation of Earth's Moon: namely, the compositional dissimilarities between the two bodies.

One idea for why Mercury is so small and has such a big core is that it got hit by something huge late in its formation that blew most of the planet's mantle away. Assuming that to be true, you could address the above point in a couple of ways:

1. Postulate that Mercury escaped from Venus by some unknown mechanism (uh oh!), and *then* got whacked by something big that blew off its mantle and left mostly core behind. However, this would require proto-Venus to effectively be a double planet with similarly sized components, since Mercury would have been so much bigger in the first place.

2. Alternatively, I guess you could start with the double-Earth idea, and then hypothesize that the impact that blew off Mercury's mantle also ejected it from Venusian orbit into solar orbit. This might work better.

I don't know if either of these ideas would ever get taken seriously. Probably not. The whole idea is most likely just not dynamically workable. Neat to speculate about, though.