Even on Earth. And that is why we don’t see them, astrophysicist suggests:
For example, could the messy chemistry we see in fossil fuels on Earth – a smorgasbord of organic reactions, a seemingly tarry chaos – be simply a short-term view of a living system that functions across hundreds of millions of years?
Or consider a chunk of complex rock, a mixture of minerals and carbon chemistry. It may be bathed for a billion years in cosmic rays and indigenous particle radiation. It changes over that timescale, electrons are freed and captured, slow, slow chemistry and structural variation happens. Your pet rock might be just that, except you’re living too fast to notice.
Of course, rather frustratingly, to make proper hypotheses for these options we need a robust definition of life, but to make that robust definition we may need to first know the extent of options for life in the universe. Caleb A. Scharf, “[article title]” at Scientific American
This general approach comes up every so often in the so-far fruitless search for life as we don’t know it. But now that we are back on solid enough ground for conventional reality to matter, our problems defining life—as we do know it—are only complicated by claims about life as we don’t.
See also: SETI reacts to the new study that says not to wait up for extraterrestrials
Researchers: We have dissolved the Fermi Paradox! (They’re NOT Out There)
Astrobiologist (Caleb A. Scharf): Why time travel can’t really work