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Life's foothold on Earth may reach back 4.4 billion years

NASA/Project Apollo Archive

(Read caption) A pockmarked lunar surface testifies to the beating the moon and Earth took during a 200-million-year period some 4 billion years ago, when asteroids hurtled into the inner solar system. Scientists at the University of Colorado have calculated that microbial life on Earth survived this pummeling, suggesting that life may have emerged on the planet as early as 4.4 billion years ago.

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Let's face it: Microbes make the contestants on CBS's "Survivor" look like pansies.

Scientists continue to marvel at the harsh conditions microbes can thrive in – and the tiny critters don't have a conniving protein in their cells.

But surely these denizens couldn't have survived the smack-around a young Earth and moon endured some 4 billion years ago. For roughly 100 million years, asteroids from the main asteroid belt between Jupiter and Mars pummeled the pair (as well as Mercury, Venus, and Mars).

Along come Oleg Abramov and Stephen Mojzsis to say, yep, it's very likely microbes survived. If that's the case, the origins of life on Earth could reach as far back as 4.4 billion years ago – far earlier than previously thought. And its trajectory through today was uninterrupted.

"Our results strongly suggest that no events since the moon's formation were capable of destroying Earth's crust and wiping out any biosphere that was present," offers Dr. Mojzsis, an assistant professor of geological science at the University of Colorado at Boulder. "Instead of chopping down the tree of life, our view is that the bombardment pruned it."

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