Hi Nick

The figure for Theia's impact is more like ~ 50 myr after the Sol System starts accreting, so there's even less time for it to all happen in. You're right that it's likely to be bullshit now you've pointed that out.

There's plenty of time for Woolfson and Dormand's collision scenario, especially since in their scenario all the asteroids we date solar system formation from condensed out of the debris of the colliding planets. No timing problem at all. The other prediction is that Mars, Mercury and Theia were once moons of one of the planets - Mercury was abraded by high-speed debris almost down to its core. If there's an age discrepancy between meteoroids and Mars and Mercury, then that might reveal important data about timing.

Adam