Does a human body decompose in a completely sterile environment ? If yes, what decomposes it ? And how fast ? What happens in vacuum ? Can it remain exactly the same ?
No it wont. Unstable molecules like ATP will quickly degrade spontaneously. The stable ones like many proteins and lipids wont degrade spontaneously. Enzymes are essential to degrade them and are to be supplied extraneously.
Body will dry up :P