I've not seen any asteroids with holes through them, so I'm assuming that this is a bug. I was flying backwards in combat when I found myself hitting an asteroid, one with the green speckles. Before I know what was happening I was inside it! I was able to turn around and fly out the other side. Once inside I didn't take any extra damage.

The collision mesh on asteroids does not always match the texture mesh, so you may be able to "hide" inside the texture of some asteroids without being harmed.

There are some donut shaped asteroids, though, and they have green semi-glowing tunnels through the middle. Did you pass through one of those?

No Starfisher, when I looked back at it there was no hole as such, just a normal looking asteroid. Celkan - that would explain it I think, thanks.

boredbypolitics, if you just got barely into the surface of the roid then it's what Celkan was talking about, otherwise it is possible to lag actually inside the roid (or at least it used to be).