“Twenty years ago it would have been considered heresy; Finding evidence of life as old as 3.8 billion years old was a shock, says Mark Harrison, study co-author and professor of geochemistry at the University of California, Los Angeles (UCLA). - Life on Earth could begin almost immediately. Given the right ingredients, life seems to form very quickly.”
“We need to think differently about the young Earth,” says Elizabeth Bell of the same university. Young Earth was certainly not a hellish, dry, boiling planet. The UCLA Geochemist Group sees no evidence of this. The planet was more similar to the current one than previously thought, scientists concluded.
UCLA scientists have found evidence that life probably existed on Earth as early as 4.1 billion years ago - 300 million years earlier than previously thought. This suggests that life may well have begun soon after the formation of the planet 4.54 billion years ago.
The study shows that life existed before the massive bombardment of the inner solar system, which left giant craters on the moon 3.9 billion years ago. “If all life on Earth died in this bombing, as some scientists are talking about, then life had to quickly reincarnate,” says Patrick Behnke, co-author of the study and a graduate student at Harrison's lab.
Scientists have long believed that the Earth was dry and desolate during this period of time. Harrison's research - including a 2008 study in Nature, which he co-authored with Craig Manning, UCLA professor of geology and geochemistry and former UCLA graduate student Michelle Hopkins - claims the opposite.
Scientists studied more than 10,000 samples of zircon, originally formed from molten rocks, magma, from Western Australia. Zircons are tough, heavy minerals associated with faux cubic zirconia that are used to imitate diamonds. They capture and preserve their immediate surroundings and can act as time capsules. The carbon found in zircon had a characteristic signature - a special ratio of carbon-12 to carbon-13 - that indicated the presence of photosynthetic life.
Scientists identified 656 zircons containing dark specks and qualitatively analyzed 79 of them using Raman spectroscopy, a technique that shows the molecular and chemical structure of ancient microorganisms in three dimensions.
Bell and Behnke, who invented chemical and mineralogical tests to determine the state of ancient zircons, were looking for carbon, a key component of life. One of the 79 zircons contained graphite - pure carbon - in two places.
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“The first time this graphite was first pulled out in 4.1 billion years was during measurements that Beth and Patrick did this year,” says Harrison.
How confident are scientists that their zircon is 4.1 billion years old graphite? “We are absolutely sure,” Harrison replies. "This is the best documented case of direct inclusion in the mineral, and no one has yet proposed a viable alternative explanation for this non-biological graphite in zircon."
This graphite is older than the zircon it contains, says the scientist. They know that zircon is 4.1 billion years old, based on the ratio of uranium to lead; but do not know how much older the graphite is. This study suggests that life in the universe could be ubiquitous, Harrison said. On Earth, simple life formed quickly, but it probably took many millions of years to simply develop the ability to photosynthesize.