More juicy awesomeness from Randall "XKCD" Munroe's "What If?" series! This week, Randy looks at what you'd get if you marshalled a mole (6.022×10^23) of moles (small burrowing rodents). First cut: you don't want to do it on Earth, as they'd have half the mass of the moon ("This smothering ocean of high-pressure meat would wipe out most life on the planet, which could—to reddit’s horror—threaten the integrity of the DNS system.") So, you stick 'em in space, where they'd form a meaty, cooling, rotting planetoid:
The mole planet is now a giant sphere of meat. It has a lot of latent energy (there are enough calories in the mole planet to support the Earth’s current population for 30 billion years). Normally, when organic matter decomposes, it releases much of that energy as heat. But throughout the majority of the planet’s interior, the pressure is over a hundred megapascals, which is enough to kill all bacteria and sterilize the mole remains—leaving no microorganisms to break down the mole tissues.
Closer to the surface, where the pressure is lower, there’s another obstacle to decomposition—the interior of a mole planet is low in oxygen. Without oxygen, the usual decomposition doesn’t happen, and the only bacteria that can break down the moles are those which don’t require oxygen. While inefficient, this anaerobic decomposition can unlock quite a bit of heat. If continued unchecked, it would heat the planet to a boil.
But the decomposition is self-limiting. Few bacteria can survive at temperatures above about 60 °C, so as the temperature goes up, the bacteria die off, and the decomposition slows. Throughout the planet, the mole bodies gradually break down into kerogen, a mush of organic matter which would—if the planet were hotter—eventually form oil.