Theoretical origin of life; zircon evidence; another article (Introduction)

by David Turell , Friday, July 06, 2018, 19:35 (2121 days ago) @ David Turell

A discussion of the findings that may push the origin of life back before four billion years ago:

https://www.quantamagazine.org/fossil-discoveries-challenge-ideas-about-earths-start-20...

"Last month, researchers lobbed another salvo in the decades-long debate about the nature of these forms. They are indeed fossil life, and they date to 3.465 billion years ago, according to John Valley, a geochemist at the University of Wisconsin. If Valley and his team are right, the fossils imply that life diversified remarkably early in the planet’s tumultuous youth.

"The fossils add to a wave of discoveries that point to a new story of ancient Earth. In the past year, separate teams of researchers have dug up, pulverized and laser-blasted pieces of rock that may contain life dating to 3.7, 3.95 and maybe even 4.28 billion years ago. All of these microfossils — or the chemical evidence associated with them — are hotly debated. But they all cast doubt on the traditional tale.

"As that story goes, in the half-billion years after it formed, Earth was hellish and hot.

***

"But this story is increasingly under fire. Many geologists now think Earth may have been tepid and watery from the outset. The oldest rocks in the record suggest parts of the planet’s crust had cooled and solidified by 4.4 billion years ago. Oxygen in those ancient rocks suggest the planet had water as far back as 4.3 billion years ago. And instead of an epochal, final bombardment, meteorite strikes might have slowly tapered off as the solar system settled into its current configuration.

***

"Taken together, the latest evidence from the ancient Earth and from the moon is painting a picture of a very different Hadean Earth: a stoutly solid, temperate, meteorite-clear and watery world, an Eden from the very beginning.

***

"In March 2017, Dominic Papineau, a geochemist at University College London, and his student Matthew Dodd described tubelike fossils in an outcrop in Quebec that dates to the basement of Earth’s history. The formation, called the Nuvvuagittuq (noo-voo-wog-it-tuck) Greenstone Belt, is a fragment of Earth’s primitive ocean floor. The fossils, about half the width of a human hair and just half a millimeter long, were buried within. They are made from an iron oxide called hematite and may be fossilized cities built by microbial communities up to 4.28 billion years ago, Dodd said.

***

“'I was taught when I was young that it would take billions and billions of years for life to form. But I have not been able to find any basis for those sorts of statements,” said Valley. “I think it’s quite possible that life emerged within a few million years of when conditions became habitable. From the point of view of a microbe, a million years is a really long time, yet that’s a blink of an eye in geologic time.”

“'There is no reason life could not have emerged at 4.3 billion years ago,” he added. “There is no reason.”

"If there was no mass sterilization at 3.9 billion years ago, or if a few massive asteroid strikes confined the destruction to a single hemisphere, then Earth’s oldest ancestors may have been here from the haziest days of the planet’s own birth. And that, in turn, makes the notion of life elsewhere in the cosmos seem less implausible. Life might be able to withstand horrendous conditions much more readily than we thought. It might not need much time at all to take hold. It might arise early and often and may pepper the universe yet. Its endless forms, from tubemaking microbes to hunkering slime, may be too small or simple to communicate the way life does on Earth — but they would be no less real and no less alive."

Comment: I've skipped over the repeated zircon evidence. This article shows life was inevitable. On purpose?