Theoretical origin of life; earliest land life (Introduction)

by David Turell , Tuesday, July 24, 2018, 17:49 (2102 days ago) @ David Turell

The earliest organic molecule signatures of possible life come from rocks that were marine in origin, not land, and have dated back to 3.8 billion years ago. Now a possible terrestrial life is found at 3.2 billion years ago:

https://www.the-scientist.com/news-opinion/oldest-evidence-of-terrestrial-life-on-a-you...

"The earliest signs of life on a young Earth, around 3.5 billion years ago, have generally come from the ocean in the form of fossilized microbes within ancient rock. Now, scientists working in the Barberton Greenstone Belt in South Africa—where some of the oldest rocks on Earth are preserved—find evidence of terrestrial microbial life that they estimate is about 3.22 billion years old. The results, published today (July 23) in Nature Geosciences, represent the oldest signs of land-based life on our planet yet discovered.

“'This work represents the oldest and least unambiguous work that we have so far that life existed on land already 3.2 billion years ago,”

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"For the current study, Homann and his colleagues focused on ancient sedimentary rocks, known as the Moodies Group, in the Barberton Greenstone Belt that were shown by geologists earlier to be approximately 3.22 billion years old. There, the team uncovered what are known as fossilized microbial mats—composed mainly of the imprints of bacteria and archaea and are among the earliest preserved forms of life. While living on the early Earth, these microbial community mats became interlayered and packed together with sedimentary rock made of rounded stones of different sizes that geologists call a conglomerate.

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"The researchers then analyzed both the organic carbon and nitrogen isotopes within these fossilized terrestrial microbial mats and compared the profiles to isotopes extracted from nearby fossilized marine microbial mats. Both the carbon and nitrogen isotope values from the terrestrial and marine samples were unique from one another, suggesting that there were differences in the metabolism of microbes in the ocean compared to those on land.

“'Already at 3.2 billion years ago, we see evidence of differences in mat-forming microbial communities suggesting that some were likely better adapted for life in the ocean versus on land,” says Homann."

Comment: This just adds to the evidence that life started very early on the newly formed Earth.