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Study Suggests That Life on Earth Began 300 Million Years Earlier Than We Thought

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According to a study published in the journal Proceedings of the National Academy of Sciences (PNAS), after studying carbon samples found in graphite embedded in zircon crystals in Western Australia, researchers believe that life on our planet may have started hundreds of millions of years earlier than previous estimates.

Elizabeth A. Bell and her co-authors explain that "evidence of life on Earth is manifestly preserved in the rock record," but the record of microfossils (so small they require a microscope to see) only goes back so far, to 3.5 billion years ago. Meanwhile, the chemofossil record (chemicals from the decomposition of a once-living organism) dates back to about 3.8 billion years ago, and the rock record to some 4 billion years ago. However, last year, zircon crystals were discovered in the Jack Hills of Western Australia that pre-date the rock record by .4 billion years, making them the oldest known minerals on the planet.

Bell and her team studied more than 10,000 Jack Hills zircon crystals and discovered the graphite and carbon samples in a "crack-free" region of the minerals. "We used the caesium ion beam to drill through the [zircon] surface and into the graphite, such that the graphite was never exposed to contaminants prior to analysis," she told Scientific American. The researchers believe that the graphite was "incorporated during crystallization of this igneous zircon." That means that if the carbons were produced by live organisms, then a "terrestrial biosphere" may have formed around 4.1 billion years ago—that's roughly 300 million years earlier than scientists previously thought.

Bell also told Scientific American that while the isotope ratio of the carbon found (which is used as an "indicator of life" in rocks) could be a result of processes that don't involve living organisms, the conditions in which the graphite was discovered would make those alternative processes "incredibly complicated, perhaps unfeasibly so."

The next step in confirming that the carbon was produced by living organisms would be to find and study more samples in the Jack Hills zircon crystals.

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Human Activity Has Permanently Altered Earth, for Better or Worse (Mostly Worse)
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Modern humans have roamed Earth for just a few hundred thousand years. In the grand scheme of things, that's a very short period. But in that time, we’ve triggered mass extinctions of plants and animals, polluted the planet, and developed nuclear weapons—and our legacy will linger in both nature and the geologic record long after historical records have been lost, according to Ted-ED’s video below.

Modern humans have altered the Earth’s landscape and atmosphere so profoundly that some scientists say we’ve ushered in a new epoch called the Anthropocene, or "new age of humankind," from anthropo (human) and cene (new). Before this, we were living in the Holocene (meaning “entirely recent”), which began around 11,700 years ago and faded sometime around 1950.

The 1950s ushered in both the plastics revolution and the atomic age, both of which permanently introduced chemicals into Earth’s fossil record. Meanwhile, humans have also shaped long-term plant and animal evolution with agriculture, fishing, and hunting. In short, our actions have long-term consequences, even if the human species ends up being a blip on the geologic time scale. Remember that the next time you drink from a plastic bottle, or see a cloud of smoke billowing through the sky.

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Spelunkers Discover New Caverns in Montréal's Ancient Cave Network
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An ancient cave system beneath a Montréal park is much more vast than experts believed, the National Post reports.

In 1812, a farmer discovered a cave underneath his property in Montréal’s present-day Saint-Léonard borough. Once used to stockpile ammunition and conceal soldiers during the Rebellions of 1837, the Saint-Léonard cave system in Parc Pie XII is today a tourist attraction and historical landmark. But some speleologists (cave experts) suspected there was more to the natural wonder than met the eye.

Beginning in 2014, two amateur explorers named Daniel Caron and Luc Le Blanc began searching for undiscovered passages in the Saint-Léonard caverns, according to National Geographic. By 2015 they had some leads; in October 2017, they used drills and hammers to break down a cave’s wall to reveal a new cavern.

The stalactite-filled chamber has soaring 20-foot ceilings, and it's connected to a serpentine network of underground tunnels. These passages formed during the Ice Age around 15,000 years ago, when glacier pressure splintered underground rock.

So far, Caron and Le Blanc have explored between 820 to 1640 feet of virgin cave passage, and expect to find even more. They believe the vast network sits atop an aquifer, and ultimately leads to the Montréal water table.

Spelunking the Saint-Léonard cave system is challenging—some passages are filled with water or require special climbing or rock-breaking equipment. The explorers hope that the caves will be easier to investigate during the dry season, and that the receding waters will allow them to reach new depths below Montréal’s surface.

[h/t National Post]

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