Diamonds hint at 'earliest life'

A diamond is FOREVER!


From the report:

slivers of diamond forged on an infant Earth may contain the earliest traces of life, a study has shown.

Analysis of the crystals showed they contain a form of carbon often associated with plants and bacteria.

The rare gems were found inside zircon crystals, formed a few hundred million years after the Earth came into being.

Writing in the journal Nature, the researchers caution that their results are not definitive proof of early life but do "not exclude" the possibility.

"We're all a little sceptical," said Dr Martin Whitehouse of the Swedish Museum of Natural History and one of the authors of the paper.

If the carbon was derived from primitive organisms, it would push back the date for life appearing on Earth by around 500 million years, to beyond 4.25 billion years ago. The Earth itself is just 4.6 billion years old.

"When you look at the carbon isotopes, they could be interpreted as biogenic because we know that biologic processes do generate light carbon isotopes. But of course there are other processes that can do that," Dr Whitehouse told BBC News.

"The most common way to form light carbon on the modern Earth is photosynthesis
Alexander Nemchin

Other possibilities include chemical reactions involving carbon oxides or even the material being delivered from space by meteorites.

However, some observers have raised the possibility that the diamonds may be contamination, introduced during polishing of the zircons.

"If you look at the photos that they present, you always see these diamonds sat in cracks and fissures and cavities," Professor Minik Rosing of the University of Copenhagen told BBC News.

If they were original features, he said, you would expect at least some to be embedded within the structure of the crystals.

"There is always fear that they might actually not be primary."

However, Dr Rosing explained, the possibility that the signatures were from early Life was "tantalising".

Time capsules

The tiny zircon crystals - just 0.3mm across - were found in the Jack Hills of Western Australia. They are the tough remnants of ancient rocks that have long since disappeared.
Map of Jack hills (BBC)

"We don't have the rocks. These zircons are just little fragments of something that was broken up, weathered and redeposited as sediments," explained Dr Whitehouse.

Radioactive dating has suggested that some of the crystals formed as far back as 4.4 billion years ago.

Scientists describe this phase in Earth history as the Hadean, and it has long been thought that it would be impossible for life to begin at this time because of the inhospitable conditions on the young planet.

But the Jack Hills zircons have begun to cast doubt on this theory.

Earlier work raised the intriguing possibility that the infant Earth would have been cooler and wetter than previously thought as the crystals show evidence of growing out of a low-temperature magma that had been in contact with water.

The new analysis of the diamond and graphite inclusions in the crystals could lend further weight to this theory.

"I think there is an interesting possibility here," said Dr Whitehouse.