According to this paper: Andrew M. Steer, Nicolas Bia, David K. Smith, Paul A. Clarke. Prebiotic synthesis of 2-deoxy-d-ribose from interstellar building blocks promoted by amino esters or amino nitriles. Chem. Commun., 2017; DOI: 10.1039/C7CC06083A, the DNA building blocks for life may have come from outer space in meteor showers:
“Dr Paul Clarke, from the University of York’s Department of Chemistry, said: “The origin of important biological molecules is one of the key fundamental questions in science. The molecules that form the building blocks of DNA had to come from somewhere; either they were present on Earth when it formed or they came from space, hitting earth in a meteor shower.
“Scientists had already shown that there were particular molecules present in space that came to Earth in an ice comet; this made our team at York think about investigating whether they could be used to make one of the building blocks of DNA. If this was possible, then it could mean that a building block of DNA was present before amino acids.”
https://www.sciencedaily.com/releases/2017/09/170914152256.htm
Imagine how the Pope will fall over himself if UFOs bring bug-eyed green intelligent life to Earth to colonise us. They will be space migrant warriors, and this will be a space invasion, but it will improve diversity. Yes, but what if the aliens decide that they want to live in the Pope’s pad?