New findings from a team of geochemists at the University of California, Los Angeles (UCLA) indicate that life on our home planet started hundreds of millions of years earlier than previously thought. The discovery was made when looking at ancient zircon crystals, and could change our understanding of early Earth.
The research team, lead by postdoctoral scholar Elizabeth Bell, made the new discovery when studying a large group of zircons – more than 10,000 in total. Zircons are useful tools for such study, as they harbor well-preserved material from their immediate environment, meaning they can be used as time capsules, providing a glimpse at the ancient past.
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Of the thousands of zircons in the study, 79 were picked out for in-depth analysis. They were examined using a technique known as Raman spectroscopy, a method that details the chemical and molecular makeup of samples, showing the data in three dimensions.
The tests were carried out in the hope of finding carbon – a key ingredient for life on Earth. The spectroscopy analysis whittled things down, and out of the 79 zircons, two were found to contain a pure form of carbon known as graphite.
So, what's so exciting about finding graphite in two zircons? Well, the mineral time capsules in question are 4.1 billion years old, making them some 300 million years older than the previous estimate for the earliest life on Earth. The findings show evidence of life not long after the formation of the planet 4.54 billion years ago, and before the period of bombardment that occurred around 3.9 billion years ago. That bombardment would have wiped out any earlier life, but it restarted very quickly.
"Life on Earth must have started almost instantaneously," said study co-author Mark Harrison. "With the right ingredients, life seems to form very quickly."
Bell concisely summed up the significance of the findings, stating simply that, in light of the discovery, "We need to think differently about the early Earth."
The researchers published the findings of their study in the journal Proceedings of the National Academy of Sciences.