Image: Artist’s concept of our Milky Way galaxy, as seen from far galactic north (the direction of the constellation Coma Berenices) via NASA/ JPL-Caltech/ R. Hurt/ Wikimedia Commons.
Laniakea, Virgo, Via Lactea, Orion Spur, Sol Terrae: Aliens are among us and within us – we call them viruses. As evolved multicellular life forms, we don’t even recognize viruses as being “alive”. I imagine that viruses consider us as aliens, or perhaps even as non-alive, in the same way as we see rocks, computers, and robots as non-alive. To a virus, our body is just a place to live like the Earth is for us. Luckily for viruses, they have billions of “virus earths” on which to live and they can migrate quite rapidly to new “virus earths” whenever they destroy the virus earth on which they feed and reproduce.
Where did these alien viruses come from? Recently, the first detection of sugars in meteorites was reported (PNAS paper: https://doi.org/10.1073/pnas.1907169116). In 2008, extraterrestrial nucleobases were found in a meteorite (https://doi.org/10.1016/j.epsl.2008.03.026). Thus far, full DNA/RNA strands or viruses have not been found on meteorites, although in 2014 an experiment showed that both are possible to survive entry into Earth’s atmosphere (https://doi.org/10.1371/journal.pone.0112979).
Given the infinite time that the multiverse has existed (with some support for this idea here: https://phys.org/news/2015-02-big-quantum-equation-universe.html), there is certainly an abundance of time for viruses to arise. The fact that all life on earth share a common ancient genetic code, and that evidence of life on Earth existing shortly after the formation of Earth, points to either a single, rare arrival on Earth or a single, rare creation event on Earth. If via arrival, then there still needs to be a single, rare creation event somewhere else. So the only difference is on the rarity of the creation event and where it occurred. Given infinite time and space, it is all but certain that viruses and life as we know it exists elsewhere.