Our Sun is considered a third generation star. What happened to generations 1 and 2? Obviously, some catastrophic event (supernova) must have happened and then all the "stuff" coalesced and we did it again. Here's my question, "What's the possibility that an earlier solar system existed, possibly with life, in those two prior generations? And since the universe is 14 BYO and our sun is about 4.6 BYO, that leaves almost 10 BY for two systems to have existed and then died. That's enough time for life to exist, isn't it?

And what elemental composition percentages make us sure that our sun is a 3rd generation star? Is it the composition of the heavy metals, those heavier than iron?