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Life on earth gets longer…

late heavy.bmp…and it’s not a director’s cut of David Attenborough

According to a Nature paper that’s receiving some pickup (Reuters, CSM ) the history of life on earth may just have got roughly 15% longer. That may not sound a huge difference, but a 15% extension on life’s lease adds up to 600 million years — roughly equivalent to the time taken for animals to get from creepy little things that couldn’t even crawl to your pet cat.

There were no animals on earth, though, during the 600 million years in question. The paper by Oleg Abramov and Stephen Mojzsis [link fixed] at the University of Colorado is about the earliest life, not the latest. Previous research has suggested that the heavy rain of asteroids, comets and the like that characterised the early solar system would have made the earth too hazardous a place for life to persist until after what is known as the “Late Heavy Bombardment” some 3.9 billion years ago. Impacts by large objects, it was thought, would vapourise whole oceans and wrap the earth in an atmosphere of superheated steam which would sterilise the planet.

The model developed by Abramov and Mojzis tells a different story. Pretty much everywhere on the planet gets zapped by a big rock, often more than once – but there are never any occasions where the whole planet including all the subsurface is simultaneously uninhabitable. If life had got started during this time, they argue, it could have persisted ever since.

At present the first evidence for life comes right after the Late Heavy Bombardment, about 3.8 million billion years ago. The speed with which that life developed after the bombardment has been seen by some as evidence that life is implicit in the way the universe is set up, and will arise spontaneously PDQ wherever it gets the chance. If it took 600 million years, though, then one would have to start thinking that life is relatively unlikely, which obvioulsy has implications for astrobiology.

It may still be the case that life arose as soon as it could, right at the beginning of the earth’s history – but it is going to be harder to prove it. While bacteria may have been able to survive the horrible early history of the earth, rocks were not so lucky – there are no major bits of crust left over from back then.

In a related happy accident, this week Nature also has a fine feature on Mike Russell and his research on the metabolism-first approach to the origins of life.

Image: simulation of the state of the Earth at the end of Late Heavy Bombardment. Circles are crater locations; colors show temperature / Oleg Abramov

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    Leon DilPare said:

    I believe you have a misprint in the fourth paragraph where it says “first evidence for life comes right after the Late Heavy Bombardment, about 3.8 million years ago”. Isn’t that 3.8 BILLION years?

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