How dense would a substance have to be before it would sink through the crust of a planet, and continue to the core?

For an example, Mars.

Thanks for the replys.

A Black hole or a neutron star would do it, but I have no idea how to calculate the density of a less extreme object.

It could be that such a density cannot be achieved with ordinary matter, without collapsing it to neutronium or a black hole. The pressure would have to squeeze out the space between molecules and perhaps squeeze out some of the space inside an atom.

Ordinary matter is mostly empty space with electromagnetic forces causing the illusion of a rigid solid object. I think you would have to overcome those electromagntic forces to squeeze out some of the empty space.

Just somewhat denser than what it's sinking through.
That's WHY things sink, of course.
But also sufficiently heavy to cause whatever it's sat on to melt enough to let it pass through.
It's not so much a question of density as it is of the relative permeability... of the "supporting" (or not in the case specified) medium.

How dense would a substance have to be before it would sink through the crust of a planet, and continue to the core?

As Oli said, it isn't a simple matter of density if you're talking about solids penetrating one another.

It depends on the strength of the crust.

Oh neat, thanks for the post. Going to digest it, and come back. Thanks alot.