Why was it important for miller and urey to sterilized the apparatus to kill any bacteria in it?

Having bacteria would produce organic molecules and defeat the whole purpose of the experiment which is to make organic molecules from inorganic molecules. The experiment was supposed to demonstrate the formation of the first organic molecules that initiated life on primordial earth. It is believed that lightning powered the formation of the first simple amino acids, like glycine, from the primordial atmosphere which was mainly composed of carbon dioxide and methane.

what bodys are there orbiting?