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Old February 22nd 19, 11:44 AM posted to sci.astro.amateur
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Default Japanese probe story on BBC: Panspermia again...

On Friday, February 22, 2019 at 12:29:07 AM UTC-5, Libor Striz wrote:
RichA Wrote in message:
Yes, they wonder if they'll find evidence that asteroids provided the basic components of life and/or water. Why is it so hard to believe it was already ON Earth??

The basic components are believed to be there.

But, what gives troubles is the short interval
between the estimated Earth age
and the age of the oldest fossil bacteria.

500 million years should be enough time for simple bacteria-like organisms to have evolved. The Earth was large, warm, already had plenty of water and other chemicals, and plenty of micro-environments were available.

There isn't any need to explain life via panspermia or explain the oceans via cometary impacts (because water was already here.) That's just kicking the can down the road. Stick with the simplest, most logical hypotheses.

It's still interesting to study the chemistry of asteroids and comets.