Microfossils, possibly world's oldest, had biological characteristics

August 16, 2018, Goldschmidt Conference
(Left) an electron microscope image of a microfossil form Strelley Pool. On the right we see the pattern of X-ray absorption for Strelley Pool, Gunflint, and modern microorganisms, with distinctive peaks indicating the presence of various molecular functional groups (including 285.1 eV for aromatic/olefinic groups, 286.7 eV for imine/nitrile/carbonyl/phenol groups, 288.2 eV for amide groups, 288.6 eV for carboxyl/ester/acetal groups, 289.4 eV for hydroxyl groups). Credit: Julian Alleon/GPL

Scientists have confirmed that the 3.4 billion year old Strelley Pool microfossils had chemical characteristics similar to modern bacteria. This all but confirms their biological origin and ranks them amongst the world's oldest microfossils. The work is presented at the Goldschmidt geochemistry conference in Boston, with simultaneous publication in the peer-reviewed journal Geochemical Perspectives Letters.

A team of scientists, led by Dr. Julien Alleon (IMPMC, Paris, France; and MIT, Cambridge, MA, USA) have been able to show that the chemical residuals from ancient microfossils match those of younger bacterial fossils, and so are likely to have been laid down by early forms.

They compared the results of synchrotron-based X-ray absorption spectroscopy analysis of the Strelley Pool microfossils with more recent ones from the Gunflint Formation (1.9 billion years old, found on the shores of Lake Superior, Ontario, Canada) and with modern bacteria.All showed similar absorption features, indicating that the residual chemicals were made from the same building blocks, thereby supporting a .

Dr. Jullien Alleon said:

"There are a couple of important points which come out of this work. Firstly, we demonstrate that the elemental and molecular characteristics of these 3.4 Ga microfossils are consistent with biological remains, slightly degraded by fossilization processes. This effectively supports the biological origin of the Strelley Pool microfossils. There are competing claims over which microfossils are actually the world's oldest, this analytical strategy needs to be applied to other ancient samples to help settle the controversy.

Secondly, it is remarkable that these echoes of past life have survived the extreme conditions they have experienced over the last 3.4 billion years: we know from the molecular structure of the microfossils that they have been exposed to temperatures of up to 300 °C for long periods. And yet we are still able to see signs of their original chemistry.

This is a step forward to confirming that these are indeed the oldest fossils yet discovered."

Commenting, Professor Vickie Bennett (Australian National University) said:

"This is exciting work with the new types of analyses providing compelling evidence that the cherts contain biogenic microfossils. This is in line with other observations for early life from the Strelley Pool rocks, including stromatolites interpreted as microbial mats, and further confirming that the minimum age for life on Earth is 3.4 billion years.

The techniques used here are not applicable to the older rocks that host the claims for the oldest terrestrial life, as these rocks were exposed to much higher temperatures. These samples include the 3.7 billion year old stromatolites from Isua, Greenland and the 4.1 billion year old Canadian . However, this work shows how quickly the field is developing and that new capabilities for testing and confirming earlier evidence of life are in reach".

Explore further: Earth's oldest fossils boost hopes for life on Mars

More information: Alleon J., Bernard S., Le Guillou C., Beyssac O., Sugitani K. & Robert F. Chemical nature of the 3.4 Ga Strelley Pool microfossils. Geochemical Perspectives Letters 7, 37-42, 2018 - DOI: 10.7185/geochemlet.1817

Related Stories

Earth's oldest fossils boost hopes for life on Mars

August 21, 2011

(PhysOrg.com) -- Microfossils found in Australia show that more than 3.4 billion years ago, bacteria thrived on an Earth that had no oxygen, a finding that boosts hopes life has existed on Mars, a study published Sunday says.

Three billion-year-old microfossils include plankton

June 6, 2013

Spindle-shaped inclusions in 3 billion-year-old rocks are microfossils of plankton that probably inhabited the oceans around the globe during that time, according to an international team of researchers.

Ancient plankton-like microfossils span two continents

July 13, 2017

Large, robust, lens-shaped microfossils from the approximately 3.4 billion-year-old Kromberg Formation of the Kaapvaal Craton in eastern South Africa are not only among the oldest elaborate microorganisms known, but are also ...

Recommended for you

Two new planets discovered using artificial intelligence

March 26, 2019

Astronomers at The University of Texas at Austin, in partnership with Google, have used artificial intelligence (AI) to uncover two more hidden planets in the Kepler space telescope archive. The technique shows promise for ...

Infertility's roots in DNA packaging

March 26, 2019

Pathological infertility is a condition affecting roughly 7 percent of human males, and among those afflicted, 10 to 15 percent are thought to have a genetic cause. However, pinpointing the precise genes responsible for the ...

Facebook is free, but should it count toward GDP anyway?

March 26, 2019

For several decades, gross domestic product (GDP), a sum of the value of purchased goods, has been a ubiquitous yardstick of economic activity. More recently, some observers have suggested that GDP falls short because it ...

Droughts could hit aging power plants hard

March 26, 2019

Older power plants with once-through cooling systems generate about a third of all U.S. electricity, but their future generating capacity will be undercut by droughts and rising water temperatures linked to climate change. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.