[#3Fan]

What if Mars were a moon of a large planet whose remnants now make up the asteroid belt? The shape of Mars suggest that it was in synchronous orbit of a large object or a large object was in synchronous orbit with it. If Mars was a moon of a large planet and that large planet disentegrated for some reason, the odds of pieces of that planet being stationary relative to Mars may be low enough that there is only two pieces (Phobos and Deimos) left today in circular orbit (interesting that Deimos is in nearly syncronous orbit). The disentagration process may be what pushed Mars to it's orbit now or perhaps the disentgration took place at the right moment in Mars' orbit around the large planet to take Mars to it's current orbit. Mars shows signs of being plastered on one side by debris miles thick, like a person's head in a pie fight. Whatever happened, it happened in one day, not over the course of thousands of years. It seems to me by measuring the nodes on Mars (nodes created by the synchronous orbit), we could estimate the size of the object that was either orbiting Mars or the object Mars was orbiting, whichever the case may be.

[RightWhale]

if Mars were a moon of a large planet whose remnants now make up the asteroid belt?

That's van Flandern's radical proposal. Nothing adds up, mass, orbits, composition, time schedule. We may never know. If we did know, it would be one of the few things we actually know.