re: Hostile Earth...
Add in the fact that the first life forms found (around 3.5 to 3.8 billion years ago) were already fairly well developed microorganisms - which means that life was around right after the end of the major celestial bombardment period of our Sol system circa 3.9 billion and possibly before.
This would be evidence at life's resilience, ability to appear, reappear, and survive even in harsh conditions, and bodes well for life evolving and thriving elsewhere.