Scientists find 3.7 billion-year-old fossil, oldest yet

August 31, 2016 by Seth Borenstein
In this photo provided by Laure Gauthiez, taken in July 2012, a field team examine rocks in Greenland. Scientists have found what they think is the oldest fossil on Earth, a remnant of life from 3.7 billion years ago when Earth's skies were orange and its oceans green. In a newly melted part of Greenland, Australian scientists found the leftover structure from a community of microbes that lived on an ancient seafloor, according to a study in Wednesday, Aug. 31, 2016 journal Nature. (Laure Gauthiez/The Australian National University via AP)

Scientists have found what they think is the oldest fossil on Earth, a remnant of life from 3.7 billion years ago when Earth's skies were orange and its oceans green.

In a newly melted part of Greenland, Australian scientists found the leftover structure from a community of microbes that lived on an ancient seafloor, according to a study in Wednesday's journal Nature .

The discovery shows life may have formed quicker and easier than once thought, about half a billion years after Earth formed . And that may also give hope for life forming elsewhere, such as Mars, said study co-author Martin VanKranendonk of the University of New South Wales and director of the Australian Center for Astrobiology.

"It gives us an idea how our planet evolved and how life gained a foothold," VanKranendonk said.

Scientists had thought it would take at least half a billion years for life to form after the molten Earth started to cool a bit, but this shows it could have happened quicker, he said. That's because the newly found fossil is far too complex to have developed soon after the planet's first , he said.

In an outcrop of rocks that used to be covered with ice and snow which melted after an exceptionally warm spring, the Australian team found stromatolites, which are intricately layered microscopic layered structures that are often produced by a community of microbes. The stromatolites were about .4 to 1.6 inches high (1 to 4 centimeters).

It "is like the house left behind made by the microbes," VanKranendonk said.

Scientists used the layers of ash from volcanoes and tiny zircon with uranium and lead to date this back 3.7 billion years ago, using a standard dating method, VanKranendonk said.

In this photo provided by Allen Nutman, a rock with the stromatolites, tiny layered structures from 3.7 billion years ago that are remnants from a community of microbes that used to be live there. Scientists have found what they think is the oldest fossil on Earth, a remnant of life from 3.7 billion years ago when Earth's skies were orange and its oceans green. In a newly melted part of Greenland, Australian scientists found the leftover structure from a community of microbes that lived on an ancient seafloor, according to a study in Wednesday, Aug. 31, 2016 journal Nature. (Allen Nutman/University of Wollongong via AP)
"It would have been a very different world. It would have had black continents, a green ocean with orange skies," he said. The land was likely black because the cooling lava had no plants, while large amounts of iron made the oceans green. Because the atmosphere had very little oxygen and oxygen is what makes the sky blue, its predominant color would have been orange, he said.

The dating seems about right, said Abigail Allwood , a NASA astrobiologist who found the previous oldest fossil, from 3.48 billion years ago, in Australia. But Allwood said she is not completely convinced that what VanKranendonk's team found once was alive. She said the evidence wasn't conclusive enough that it was and not a geologic quirk.

"It would be nice to have more evidence, but in these rocks that's a lot to ask," Allwood said in an email.

Explore further: Bacteria could aid search for creatures on other planets

More information: Allen P. Nutman et al. Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures, Nature (2016). DOI: 10.1038/nature19355

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16 comments

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TheGhostofOtto1923
3.8 / 5 (13) Aug 31, 2016
"Scientists have found what they think is the oldest fossil on Earth"

-Now now I think its a safe bet theres one out there thats at least a week or so older.
Azrael
4.6 / 5 (10) Aug 31, 2016
Pretty freakin' cool if it can be verified. It certainly "looks" like a stromatolite fossil.

It's also rather neat that communal organisms much like this are still around today. They seem remarkably successful.

GaryB
4.3 / 5 (4) Aug 31, 2016
Why can't I get the picture out of my mind of aliens whose brains look like stromatolites visiting early earth? Well, this is pushing the timeline of life way back. In some sense, these bacterial mats can be viewed as proto-multi-cellular creatures.
Mark Thomas
2.6 / 5 (8) Aug 31, 2016
"That's because the newly found fossil is far too complex to have developed soon after the planet's first life forms, he said."

Panspermia is looking better all the time, especially considering the Late Heavy Bombardment (4.1 to 3.8 billion years ago) didn't end all that much before this fossil formed 3.7 billion years ago.
humy
5 / 5 (4) Sep 01, 2016
"..Because the atmosphere had very little oxygen and oxygen is what makes the sky blue, its predominant color would have been orange, he said...."

...then he is wrong: false inference. The reason why the sky appears blue is mainly because of the presence of nitrogen, not oxygen. Although oxygen does scatter some blue light thus contribute to the sky being blue, most of the blue color in the modern sky comes from the presence of nitrogen which I presume would have been abundant in the early earth's atmosphere? In any case, regardless of what the color was of the atmosphere of early earth, an atmosphere can appear blue even if it has no oxygen depending on the types of gases and in what proportion the atmosphere does have.
humy
5 / 5 (3) Sep 01, 2016
-to add to that:

An example of a blue sky with little/no oxygen would be that of Neptune;
http://www.space....ere.html
torbjorn_b_g_larsson
5 / 5 (2) Sep 01, 2016
Scientists had thought it would take at least half a billion years for life to form after the molten Earth started to cool a bit, but this shows it could have happened quicker, he said.


The cool early Earth is fairly established, with oceans before 4.3 billion years ago, and there is no fundamental reason why life didn't emerge then. That would comply with molecular clocks (Bacteria and Archaea split before 4.2 billion years ago) as well as the first putative fossils (before 4.1 billion years ago).

@Mark: Transpermia (between near planetary bodies) is in fact put in tension by early dates. Mars's habitable period is later than Earth's..(And *if* the arguable late bombardment happened it didn't need to sterilize, as these results imply.)
Mark Thomas
1.3 / 5 (4) Sep 02, 2016
@tbgl, regarding transpermia, that is probably right. This favors a panspermian origin beyond the solar system so that life was ready as soon as the Earth was. This seems possible, or even likely, given the vast amount of suitable time before the solar system formed and the vast amount of impacts scattering rocks (and potentially bacterial passengers) during that time.

On Earth, bacteria seem to fill every survivable niche available. It does not seem unreasonable to wonder if that is true in space as well.
tinitus
Sep 02, 2016
This comment has been removed by a moderator.
shavera
5 / 5 (1) Sep 02, 2016
I find panspermia pretty dubious when you consider how primitive the earliest forms of life seem to be. If life started elsewhere and came here, why would it be so 'simple'? It's not a hard scientific argument, just feels implausible. Like whatever life leaves earth and travels off into space, whatever makes it to the next planet doesn't seem like it'd be anything like the early life of our own planet.
FredJose
1 / 5 (6) Sep 02, 2016
a remnant of life from 3.7 billion years ago when Earth's skies were orange and its oceans green.

This is pure speculation and story telling, of course. There is no supporting evidence that this was the case. And in fact is based on another mythical assumption, below:
shows life may have formed quicker and easier than once thought, about half a billion years after Earth formed

Firstly, it is just physically and chemically impossible for life to "form" all by itself from purely random chemical and physical processes. Such a thought pattern goes against all established scientific principles of chemistry.
Furthermore, the earth itself could not have "formed" out of a cloud of dust all by itself. This idea goes against the established principles of physical mechanics. There is absolutely ZERO evidence that planets can arise out of a cloud of dust all by themselves. No one has seen such a thing nor is anyone able to confirm it can happen.

tinitus
Sep 02, 2016
This comment has been removed by a moderator.
jonesdave
3.7 / 5 (6) Sep 02, 2016
@FredJose,
It is better than the "mythical assumtion" (if ever there was one!) that some god or other did it! Numerous experiments have shown that Earth analog atmospheres from this date can provide the precursors to life. So, more evidence than the "god did it" brigade.
As for planets coming from dust clouds; perhaps you should look at the various images that have been seen of planets forming in just such dust clouds around other stars. Again, more evidence than anyone else has to offer.
torbjorn_b_g_larsson
not rated yet Sep 03, 2016
@Mark: Okay, but panspermia is unrealistic due to the vast distances.

And there is no niches in space for liquid water based life. (Background temperature ~ 3 kelvin.)

So I don't think that goes anywhere.

@tinnitus: - It isn't "too" tiny, stromatolites don't have a minimum size until they can't be distinguished from the variance in surrounding bacterial mats.

Also, I still haven't read the paper, but other images show lamination.

- There is no evidence of life (cells, viruses) 'raining down' from space, obviously, That would be huge news.

To repeat myself, early emergence put transpermia in tension. And panspermia is unrealistic.
torbjorn_b_g_larsson
5 / 5 (2) Sep 03, 2016
@Fred: - This work is no different in scope than related work. See the article.

It is your claim of 'story telling' that is story telling. Bad story telling, easily revealed as such.

- It is no more 'impossible' for life to emerge than when the planet itself emerged. In fact, a major theory predicts that these processes are related, and it is tested by similar outcomes on Enceladus (serpentinization and organics from primordial geology).

As phys.org readers know well, planets are observed forming in a number of ways, from element and isotope ratios of molecular clouds to imaging. [ http://news.natio...g-space/ ]

If you are going to discuss science, you should do due diligence and check on these things. Before making claims that are obviously erroneous for most readers, and easy enough to check with google in a few seconds.

Another thing, you keep repeating claims that has been shown to you are wrong. Dumb or 'evil'?
TheGhostofOtto1923
4.5 / 5 (2) Sep 04, 2016
And there is no niches in space for liquid water based life. (Background temperature ~ 3 kelvin.)
I was wondering if a planetary fragment could contain enough uranium to heat it's interior enough to sustain liquid water. I searched a little bit and found nothing. A collision could sent fragments on interstellar paths.

There's also the possibility that spores or something similar could survive the journey.

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