What is true of the first organic molecules on earth?
Organic matter is anything made of carbon. Unless there exists other unknown criteria for life (as we don't know it!) yet to be discovered, it is at present reasonable to assume that carbon is one element indispensable for life, at least on our "terms."
As other elements, carbon does not just exist on earth. The elements such as we have classified on the periodic table compose the common denominator, so to speak, of the universe.
The atmosphere on earth has, however, modified the nature and quantity of certain substances found on its surface since it acts as a screen. When meteors and other "debris" are pulled into the earth's gravitational field, most matter is burned up along the way. For this reason, certain substances (such as helium 3) rare on earth are abundant on spheres without atmosphere, such as the moon. Scientists are already considering its potential (helium 3) as a replacement for fossil fuel.
Your question is as big as the universe! Could you focus on something more specific? Let's hope then that a physicist joins the ranks of enotes to give you a most professional reply!