Diamonds really are forever: Study

·2-min read

Ancient diamonds indicate earth was primed for life's explosion at least 2.7 billion years ago, researchers say.

Volatile gases conserved in diamonds discovered in ancient rocks were present in similar proportions to those found in the earth's mantle, which lies between the planet's core and crust.

This indicates there has been no fundamental change in the proportions of these gases in the atmosphere over the last few billion years.

The research suggests one of the basic conditions necessary to support life - the presence of life-giving elements in sufficient quantity - appeared soon after earth formed, and has remained fairly constant ever since.

Presenting the work at the Goldschmidt Geochemistry conference, lead researcher Doctor Michael Broadley said: "The proportion and make-up of volatiles in the atmosphere reflects that found in the mantle, and we have no evidence of a significant change since these diamonds were formed 2.7 billion years ago."

Volatiles such as hydrogen, nitrogen, neon, and carbon-bearing species are light chemical elements and compounds, which can be readily vaporised due to heat, or pressure changes.

They are necessary for life, especially carbon and nitrogen.

On earth, volatile substances mostly bubble up from inside the planet, and are brought to the surface through events such as volcanic eruptions.

Knowing when they arrived in the earth's atmosphere is key to understanding when the conditions on the planet were suitable for the origin and development of life.

Now French and Canadian researchers have used ancient diamonds as a time capsule, to examine the conditions deep inside the earth's mantle in the distant past.

Studies of gases trapped in the "comparatively indestructible" diamonds show the volatile composition of the mantle has changed little over the last 2.7 billion years.

Researchers studied diamonds trapped in 2.7 billion-year-old highly preserved rock from Wawa, on Lake Superior in Canada.

This meant they were at least as old as the rocks they were found in - probably older.

The diamonds were heated to more than 2000C to transform them into graphite, which then released tiny quantities of gas which was measured.

The team measured the isotopes of helium, neon, and argon, and found they were present in similar proportions to those found in the upper mantle today.

This suggests the distribution of essential volatile elements between the mantle and the atmosphere are likely to have remained fairly stable throughout the majority of earth's life.

"This was a surprising result," Dr Broadley said.

"It means the volatile-rich environment we see around us today is not a recent development, so providing the right conditions for life to develop.

"Our work shows that these conditions were present at least 2.7 billion years ago, but the diamonds we use may be much older, so it's likely that these conditions were set well before our 2.7 billion year threshold."

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