ANCIENT EVIDENCE

The 3.7 billion-year-old fossils discovered in Greenland might be proof that there’s life on other planets

Although sparsely populated by people, Greenland is home to some really old life. The sharks that patrol the country’s coast are the oldest living vertebrates on the planet. And the ice-covered island hosts the remains of some of Earth’s most ancient bacteria—maybe the oldest evidence of life we’ve found on the planet so far.

On Aug. 31, a team of Australian and British researchers published (paywall) work in Nature describing the oldest fossils discovered yet, from about 3.7 billion years ago. The fossils were comprised of layers of bacterial goo called stromatolites, and indicate that life bubbled up on Earth relatively shortly after the planet formed 4 billion years ago.

Stromatolites are the distinctly structured remains formed when layers of microbes trap minerals, like carbon and sulphur, beneath them. In this case, they were found in the forms of tiny cones, between one and four centimeters (less than two inches) tall. Allen Nutman, a geologist from the University of Wollongong in New South Wales, and his team found the structures in 2012 on the eastern tip of Greenland, in a place called the Isua Greenstone Belt, which also happens to be the home of Earth’s oldest rocks from about 3.8 billion years ago. Labs confirmed the presence of carbon dioxide and a few other trace chemicals from 3.7 billion years ago. Life, then, would have originated even earlier, because these structures can only be formed by bacteria that evolved from much more basic lifeforms.

Granted, these fossilized stromatolites don’t necessarily verify the presence of ancient microbes themselves. And stromatolites can be difficult to distinguish from formations created by minerals. “I’ve got 14 queries and problems that need addressing before I’ll believe it,” Roger Buick, a geobiologist at the University of Washington in Seattle, told Nature. It’d be helpful to know, for example, if there were other kinds of organic material left in the fossils to definitively say they were the result of bacteria.

If these fossils are tokens of ancient life on Earth, it’s one more reason to believe we’re not alone in the universe.

Scientists still aren’t exactly sure how life kickstarted itself on our planet all those billions of years ago. But if it’s true that there were microbes here 3.7 billion years ago, it means “the origin of life, at least on a planet like ours, is a lot faster, and you think a lot easier than anyone had imagined,” J. William Schopf, a paleobiologist at the University of California, Los Angeles, told the Washington Post. “To the extent that that is true, life ought to be abundant in the universe—because there are lots of Earth-like planets out there.” Like Proxima B, a planet located just outside of our solar system that scientists say could have water on it, based on it’s estimated size and temperature.

Or maybe even a closer astronomical object. Around 3.7 billion years ago, water (widely considered the key ingredient to life) was here on Earth. And NASA has reported strong evidence that at the same time, water existed on Mars (although these claims have been questioned).

“Mars was wet,” Nutman told the Washington Post. “If life had managed to evolve to produce structures like stromatolites by 3,700 million years ago on Earth, there is an increased probability—certainly not a certainty—that the same type of process might have happened on Mars before it dried out.”

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