Before we can answer this question intelligently, I think we need to answer another one: How would you decide if a thing is a form of life, or not? Suppose you are walking along the beach, and there's this purple blob lying in the surf. Is it alive? I submit that the phenomenon must be examined over a suitable duration. That's because life is characterized by processes, not mere static structures, that occur in time. Ingestion of matter/energy, growth, reproduction, all take time. There's an arrow in time for all living processes. It's as though living things are moving toward some goal. The material components exist and take their properties from the need to 'function', i.e. to support the essential processes of life. The best you can do by merely inspecting or dissecting the structure of the purple blob is to determine if it once was living. Perhaps, try a thought experiment. You are exploring and exoplanet and you come across something like the purple blob, how would you know if it is alive or not?
Life, the thing and the process, has to take in energy and matter in order to create more of itself. Just guaranteeing that genetic information is faithfully copied imposes costs in energy on systems that correct the errors that inevitably occur during replication of that information. The growth of information, which is what replication is, is equivalent to loss of entropy. The highly ordered, information-containing and propagating structures of living organisms cannot exist for very long if entropy holds sway. The entropy of a system can only decrease if energy is added to it, which requires influxes from the environment. Thus, living organisms must be open systems, thermodynamically speaking, in order to defeat the second law. And of course reproduction of an organism requires that it increase in mass between reproductive events.
We don't have to go to exoplanets to confront the question. There are the viruses. You can sample a batch of viruses to see if it creates more of them. It won't. So are viruses alive? Not by themselves. You can only uncover evidence they are alive when the viruses are exposed to the right kinds of living cells. In order to exhibit a living process, viruses must steal matter and energy from other life forms to carry to grow and reproduce. Regardless of how and where they do it, I would consider viruses living. But again, I would have to spend time with viruses before I could answer the question. The other candidates I have in mind are the prions. Prions are protein molecules that reproduce themselves inside living organisms which, like viruses, die from the internal buildup of these molecules. Are prions living? I"m not sure...
