Much news about carbonaceous meteors has trickled in. In particular they constrained the Allende.
This became a meteor at Earth AD 1969 so "51 ya" I suppose. Its asteroid got to our part of the solar-system 4562 Mya. That's only five million after the first asteroids of any sort. Before that - they now agree - this parent asteroid was an undifferentiated clayball like Ceres and unlike Vesta. It never did get a core.
They think that this constrains when Jupiter began its "grand tack". The asteroids would have formed on either side of the giant planet. Then Jupiter moved... somewhere. Doesn't much matter where. This brought carbonaceous rocks, which belong I assume about where Ceres is at, to an (eventually) Earth-crossing orbit.
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