Could life on Earth have started 300 million years earlier than scientists previously thought? After taking a closer look at ancient minerals formed from molten rocks, researchers from the University of California, Los Angeles (UCLA) think so. Hidden within these structures that capture their geologic background, researchers found dark specks that resembled ancient microorganisms. This evidence has ultimately changed the way scientists view the Earth following its formation 4.5 billion years ago.
"Twenty years ago, this would have been heretical; finding evidence of life 3.8 billion years ago was shocking," Mark Harrison, co-author of the research and a professor of geochemistry at UCLA, said in a news release. "Life on Earth may have started almost instantaneously."
UCLA geochemists examined tiny grains of the mineral zircon--related to cubic zirconia, used as fake diamonds--found within molten rocks, or magmas, from western Australia's Jack Hills. Hidden within the grains, researchers found what they call a "chemo-fossil" or a certain mix of carbon isotopes, which often indicate the presence of life. After dating these findings, they believe they have found evidence suggesting that life existed on Earth at least 4.1 billion years ago, according to the release.
While scientists have long thought that early Earth was a dry and desolate place where there would not have been enough water to sustain life, with the right ingredients, life can sprout up fairly quickly, Harrison explained. This new research also suggests that life existed before the massive bombardment of the inner solar system 3.9 billion years ago, the release noted.
"The early Earth certainly wasn't a hellish, dry, boiling planet; we see absolutely no evidence for that," Harrison added. "The planet was probably much more like it is today than previously thought."
Zircons are heavy, durable minerals that basically act as time capsules, since they store important information regarding their immediate environment. For their study, researchers identified 656 zircons containing dark specks, 79 of which they closely examined with Raman spectroscopy. This technique allowed them to see the molecular and chemical structure of the ancient microorganisms in 3D. When analyzing the zircons, researchers were specifically searching from carbon, which is the key component of life.
There are different types of carbon with different weights preserved in what scientists call "carbon signatures." Within one of 79 zircons, researchers discovered graphite, or pure carbon, in two locations. From this, researchers determined the zircon is 4.1 billion years old, based on its ratio of uranium to lead, and that the graphite it contains is even older.
"There is no better case of a primary inclusion in a mineral ever documented, and nobody has offered a plausible alternative explanation for graphite of non-biological origin into a zircon," Harrison said.
Based on the carbon signatures, researchers also discovered a specific ratio of carbon-12 to carbon-13. This indicates the presence of life forms that could perform photosynthesis, researchers explained in their study.
Researchers believe that this not only changes the way we view early Earth, but also that life in the universe could be much more abundant than current knowledge leads us to believe.
"We need to think differently about the early Earth," Elizabeth Bell, lead researcher of the study and a postdoctoral scholar in Harrison's lab, said in a statement.
Their study was recently published in the journal Proceedings of the National Academy of Sciences.
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