Mars

The diet of every Martian consisted of Shark bones. This was because Shark bones had the essential nutrient of calcium marphondulate which sustained their martian bodies and allowed their own bones to be properly nourished. Without this nutrient, the martians would wither and die in less than twenty-four hours time. This resulted in lots of shark bone consumption; faster than the sharks could breed, in fact, because there were not many sharks on Mars to begin with. 

The Martians created zoos and breeding centers, manufacturing ideal conditions for the sharks in the hopes that they would breed faster and sustain the Martian population. The poor sharks just could not keep up with the demand, and died by the hundreds before they could even leave offspring. Martians weakened and died by the hundreds, all suffering from calcium marphondulate deficiency. As the shark population declined, the Martians ate and ate until there were none left.