May 10, 2017

Fossil Find Could Rewrite the Record of Life on Earth

A microscopic image of geyserite textures from the ancient Dresser Formation shows surface hot spring deposits from 3.5 billion years ago.
Ancient hot spring deposits found in Australia’s desert could help unlock the mystery of how life evolved on Earth, and provide clues for scientists searching for extraterrestrial existence, according to a new study.

A team of scientists scouring the remote Pilbara region of Western Australia have uncovered evidence of fossilized microbial deposits that extend the geological record of life in hot springs.

The discovery could have important implications for our understanding about the origins of life, the researchers say, because it suggests it may have evolved on land, rather than deep in the ocean.

“Prior to this work, the oldest evidence of life on land was 2.7 billion years old. That wasn’t in hot springs, it was in South Africa in rich soils. Basically, that was an argument to say: ‘We don’t see life on land very early on, it must have adapted later,’” said lead author Tara Djokic of the University of New South Wales. “Now, we are seeing life was already on land 3.5 billion years ago.”

The findings were published today in the journal Nature Communications.

The Dresser Formation in western Australia.
Currently, there are two competing hypothesis for the origin of life. Either it evolved in deep sea hydrothermal vents or, as Charles Darwin theorized in his “warm little pond scenario,” it was sparked by the mixing of chemicals on land.

Scientists published details last year of what is thought to be the oldest evidence of life on Earth, which was found in Greenland. The 3.7 billion-year-old fossil stromatolites were located on the sea floor.

Djokic said the discovery of fossils in the Dresser Formation in the Pilbara Craton provides a new geological perspective that supports Darwin’s theory.

“I don’t think the Dresser Formation is anywhere close to the origin of life, but it does lend weight to that environment being available, which was previously not known,” she said.

Among the fossils found in the harsh, dry environment were layered rock structures created by communities of ancient microbes, called stromatolites, and preserved gas bubbles.

Evidence of geyserite, which helped preserve the fossils, provided the “smoking gun” that the deposits had a terrestrial origin, Djokic said. Geyserite is a silica-rich mineral deposit that is only found in a land-based, hot spring environment.

The findings show there was life on land up to 580 million years earlier than previously thought.

Read more at Discovery News

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