[Chris2048]

> oxygen-rich atmospheres probably indicate life

Is it though? We only have one example of "life" and that is an oxygen based form. Supposing all forms of life are similar is something I consider unproven.

It might be more accurate to say an "unusual" planetary chemistry is indicative of an unusual process, which might include life. But then the question is: How many planets are there with unusual chemistry? I think we are far from observing this - the many planets we now suppose to exist are only just being discovered, starting with the largest, the hottest, and the nearest.