Cracked rotor

While doing some maintanance, I found cracks on my rear brake Rotor. Anybody with any experience with this? Came kinda out of the blue, have no idea how my trips I already did on it like this and new (bigger) rotor will be delivered...soon (yet still a few days).
Unless weather goes rainy or temperature drops significantly, I don't want to just sit at home wainiting, unless really necessary ...

 

Best picture from like eight or something, just to get exactly that effect :-D
As already mentioned elswhere, that rotor gets a LOT of heat beating, so perhaps...
As I don't know when or how it can crack even more, new one is on its way. 203mm dia. AFAIK thickness is more or less universal, maybe there are two "standards" as Shimano goes for 1,8mm and Hayes for 2,0mm, but that's it. Diameters however you can get 140, 160, 180, 203 [mm], so I am pushing envelope here :-D You can swap them as you wish, being that a standard parts, there are different mounts for them on shleves as well. Hopefully it will ease some of those heat issues...
Delivery date also stopped being an issue, as I met a van head on right after that first post (driving on the right side is for noobs, once you drive big box, right?), so plenty of time to put everything in order...

 

Delivery was finally ...delivered. and its a MONSTER. Sporting 2x 180 on front and soon one 203 on rear, I can certainly say that I am not underplaying braking power on my rig...