Tuesday, September 30, 2008

Origin of life: Oldest Earth rocks may show signs of life, in which case, ...

In "Team finds Earth's 'oldest rocks'" (BBC News, September 26, 2008) James Morgan reports:

Writing in Science journal, a team reports finding that a sample of Nuvvuagittuq greenstone is 250 million years older than any rocks known.

It may even hold evidence of activity by ancient life forms.
Geologist Don Francis and graduate student Jonathan O'Neil of McGill University in Montreal have found an ancient greenstone ("faux amphibolite") which may be the oldest rock known.

The rock was dated to between 3.8 and 4.28 billion years ago. "4.28 billion is the figure I favour," says Francis. It is not surprising that he favours the latter date, since it would make his find about 250 million years older than the second oldest one, the Acasta Gneiss in Canada's Northwest Territories, dated at 4.03 billion years old.

But now what's this about life? Well, honestly, right now, it's mostly imagination. The greenstone shows a banded iron formation of magnetite and quartz also found in rock around deep sea hydrothermal vents. Many think that these vents hosted early life on earth.
"These ribbons could imply that 4.3 billion years ago, Earth had an ocean, with hydrothermal circulation," said Francis.

"Now, some people believe that to make precipitation work, you also need bacteria.

"If that were true, then this would be the oldest evidence of life.

"But if I were to say that, people would yell and scream and say that there is no hard evidence."
O'Neil adds,
We know that probably the right environment was there for life to be on the Earth -- so liquid water and all it takes to have life. Now was there life? This is a big question mark"
Actually, the geologists are probably safe. People are pretty open to speculation around the origin of life. But let us say that their wildest dreams come true an they do find hard evidence of life in these rocks. In that case, life started on Earth almost immediately after the planet cooled (in geological terms, that is). If so, then life clearly did not originate via a long slow random swish of chemicals, as we have been encouraged to believe.

Francis and O'Neil had been looking for clues on the eastern shore of Hudson Bay in northern Quebec about the Earth's mantle from 3.8 billion years ago when they found the outcrop of the Nuvvuagittuq greenstone belt. It was dated at the Carnegie Institution of Washington by measuring the isotopes of neodymium and samarium, rare elements that decay at a known rate.

Here are some other "oldest rocks" stories, and some photos put up by Professor Francis.

See also

Origin of life: Positive evidence of intelligent design?

Origin of life: But is being greedy enough?

Origin of life: Ah, that "just so happens" intermediate series of chemical steps

Why should the search for Darwin's "warm little puddle" be publicly funded?