Energy required to fracture a planetary mass

[bitrex]

Energy required to "fracture" a planetary mass

I was playing around with the Impact Effects calculator at http://www.lpl.arizona.edu/impacteffects/ and doing some thinking about the impact event scenario of the Moon's creation. The main bulk of the Earth seems to have stayed in one piece after that collision, though it lost a significant fraction of it's mass. As an intellectual exercise I was wondering how one might go about calculating the amount of energy that would be required to actually "fracture" a planetary sized mass into pieces that would not remain contiguous. I imagine it would have to be some large fraction of the body's gravitational binding energy, but as I'm not an astrophysicist I don't know what kind of starting assumptions one would make when dealing with such a problem.

I'm sure many collisions of similarly-sized large planetary bodies occurred in the early evolution of the Solar System, but perhaps large bodies don't "fracture" in the way I'm thinking and collisions are more fluid? Any insight to help satiate my curiosity would be much appreciated!

 

[mgb_phys]

Correct - it's all fluid dynamics, on these scales the crust doesn't have any mechanical strength so it's like a blob of water splitting in two.

 

[gtring]

I'm curious about the extreme situations. Would an atmosphere (not necessarily Earth's atmosphere) also play a role here? How about a planet with a large magnetic force? Or would these be completely minor players compared to the fluid dynamics of it all?

Cheers,
--Jake