Ancient diamonds may hold the key to life on Earth

Diamonds contain trapped chemicals that provide clues to the composition of Earth’s atmosphere when they were formed. Volatiles like nitrogen, hydrogen, neon, and other carbon bearing species are light chemicals necessary for life.

The chemicals develop deep in the Earth and come to the surface during volcanic eruptions. Not all planets are rich in these chemicals, so much of the search for extraterrestrial life is done by looking for volatiles. 

In a recent study led by Dr. Michael Broadley, researchers looked at the composition of volatiles in a 2.7-billion-year-old diamond. The diamond has within it a snapshot of the composition of the Earth’s mantle and by extension the atmosphere at the time.

“Studying the composition of the Earth’s modern mantle is relatively simple,” said Dr. Broadley. “On average the mantle layer begins around 30km below the Earth’s surface, and so we can collect samples thrown up by volcanoes and study the fluids and gases trapped inside.” 

“However, the constant churning of the Earth’s crust via plate tectonics means that older samples have mostly been destroyed. Diamonds however, are comparatively indestructible, they’re ideal time capsules.”

“We managed to study diamonds trapped in 2.7 billion year old highly preserved rock from Wawa, on Lake Superior in Canada. This means that the diamonds are at least as old as the rocks they are found in – probably older. It’s difficult to date diamonds, so this gave us a lucky opportunity to be sure of the minimum age.”

“These diamonds are incredibly rare, and are not like the beautiful gems we think of when we think of diamonds. We heated them to over 2000 C to transform them into graphite, which then released tiny quantities of gas for measurement.”

The diamonds turned out to have roughly the same composition of volatiles that are present in the Earth’s upper mantle today. 

The scientists were surprised by the results. They said this means that conditions on Earth were suitable for life 2.7 billion years ago, and potentially much earlier. 

The research was presented.at the Goldschmidt Geochemistry Conference.

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By Zach Fitzner , Earth.com Staff Writer