I see. Well, to clearly identify this as an actual orb (even if it's broken), you will have to change the shading, as it currently looks like an erythrocyte.
So basically, the middle looks flat, while the outside is elevated.
Basically, keep the cracks the way they are, simply create an additional layer where you apply the correct shading. By highlighting the correct edges of the cracks (depending on where the light source is), you will get the look you are looking for.
If you feel like I am being too unspecific or unclear, feel free to ask, I can also provide examples, if you need/want them.