Alternative chemistries for life
Ammonia, silicon, and hydrocarbons can theoretically support life.
To make life on Earth, just follow this simple recipe: Combine generous portions of carbon, hydrogen, oxygen, and nitrogen to synthesize organic molecules. Sprinkle into water, a handy solvent to facilitate chemical reactions. And don't forget the energy source — perhaps a warm little pond maintained at a higher temperature than its surroundings by a nearby volcanic hot spring.