Scientists have found a new way to stir their primordial soup to get the building blocks of life to start assembling. “[Their] study unites two prominent origin of life theories – the ‘RNA world’, where self-replicating RNA is proposed to be fundamental, and the ‘thioester world’, in which thioesters are seen as the energy source for the earliest forms of life”.
Put 5 biologists in a room and ask this question and you’ll get 5 different answers :)
But generally you’d be looking for at least some signs of:
Fire really fucks things up, because it’s really easy to accidentally define it as living.
No cellular organization
There’s no reason to think life on other planets would specifically have cells. That’s a rule we made up specifically because of fire.