Gunnerkrigg Court 3: Mystery Solved!

[Landis963]

I'm calling it: Jones is the dense object around which stellar dust accumulated, leading to the eventual formation of Earth.

Where she came from before that is anyone's guess.

But then why would she be close enough to the surface to be unearthed during the Silurian period? Dust gathering around her to form the Earth would by necessity put her at the center of the Earth. Unless she deliberately moved away from the core, in which case the first thing we saw of her during the Silurian period should have been her hand, not her face.