I don't like this question because beyond solar system exploration it can not be proven or tested. Only testable hypotheses are worthwhile.
Better to concentrate on understanding how life developed here on Earth. I think the starting point is water. NASA's Asrobiology program features the mantra 'Follow the water' for wherever you find liquid water on Earth you find life.
My research at the moment considers the impact of protective osmolytes such as TMAO on biological molecules such as peptides in water. You can not hope to answer questions about aliens unless you understand the basis of life at the molecular level. We do not undertand the behaviour of even one of the simplest compounds in the universe which is water. In fact liquids are not simple. They are incredibly complex. Crystals are uniform repeating structures whereas liquids change all the time, and to understand their behaviour you have to understand enthalpy and entropy.
I am studying the behaviour of water molecules in association with co-solutes like urea and TMAO (which occur in animals) to study their effect on water.
I use NMR spectroscopy to measure the changes in the hydrogen bonding network as I change the concentration of solutes, and I can also measure diffusion coefficents and rotational relaxation. Through this and complementary techniques we can better understand the interaction of molecules at the molecular level. What controls the shape of proteins in solution? I think that it is by addressing problems like this that you chip away at problems like how common is life. Complex chemistry forms readily in the presence of water. Ribose sugar forms in the ISM but we don't understand how you go from relatively simple biomolecules like this to the complexity of life.
It's always a question of learning what we know now, then finding a research question and taking tiny steps.
Although it is simple to say the universe is huge and therefore there are an infinite number of possibilities where do you go beyond that? You need to be specific. solar system samples? Some people study organic chemistry in meteorites. One of the most interesting samples I know of is the Hag meteorite. Liquid droplets containing organic molecules trapped inside halite crystals that formed on another world,and we even think we know which world. Ceres is the best bet. What was the state of the early solar system, the pre-existing state of pre-biotic chemistry at the very start of life? We know that. What is the connection between organic chemistry and chemistry of protoplanetary disks? is it destroyed? These are good questions, and things to study.
