Do not blame NASA guys for thinking a stone to be a skull. After all, they ought to have a stone up there in their skull, to be not able to differentiate between a skull and a stone! Regards, RightMan
It is more probably a rock, shaped like a skull. If it belongs to Martian, then fellow Martian could have taken it for cremation
They also say they found a robot head on the moon, which there is pictures proofing this very crazy. We are obviously not the first to visit these other planets or to even inhabit them.