The key to identifying a Combustion reaction is

Good signs that you're dealing with a combustion reaction include the presence of oxygen as a reactant and carbon dioxide, water, and heat as products. Inorganic combustion reactions might not form all of those products but remain recognizable by the reaction of oxygen.

i'd say that the moon rock is about 2.2 billion years old.

the sphincter muscles at the end of the digestive tract is the anus.