http://www.abc.net.au/news/2015-10-20/ancient-crystals-reveal-life-could-be-older-than-thought/6870678

Ancient crystals unearthed in Western Australia may contain evidence that life existed hundreds of millions of years earlier than previously thought.

The multi-billion-year-old zircon crystals were found at Jack Hills, about 600 kilometres north-east of Perth, a site well known for the mineral grain, which is so far the oldest known material ever identified on dry land.

I’d like to read the original paper.

Well here’s the abstract
http://www.pnas.org/content/early/2015/10/14/1517557112.abstract

And here’s the paper
http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf

dv said:

Well here’s the abstract
http://www.pnas.org/content/early/2015/10/14/1517557112.abstract

Thanks. Most interesting. I reckon there might be a few more carbon inclusions in Jack Hills zircons looked at in the near future.

:)

dv said:

And here’s the paper
http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf

Hey thanks.

Looks like they have already looked at a lot of zircons…

Their interpretation of the data is reasonable.

Michael V said:

dv said:

And here’s the paper
http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf

Hey thanks.

Looks like they have already looked at a lot of zircons…

Their interpretation of the data is reasonable.

—

But, but, is the carbon naturally formed?

tauto said:

Michael V said:

dv said:

And here’s the paper
http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf

Hey thanks.

Looks like they have already looked at a lot of zircons…

Their interpretation of the data is reasonable.

—

But, but, is the carbon naturally formed?

All carbon is naturally formed

tauto said:

Michael V said:

dv said:

And here’s the paper
http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf

Hey thanks.

Looks like they have already looked at a lot of zircons…

Their interpretation of the data is reasonable.

—

But, but, is the carbon naturally formed?

Gawd, I do hope it’s not some of that inorganic crap.

dv said:

tauto said:

Michael V said:

Hey thanks.

Looks like they have already looked at a lot of zircons…

Their interpretation of the data is reasonable.

—

But, but, is the carbon naturally formed?

All carbon is naturally formed

—-

oops, biogenetically formed.

dv said:

And here’s the paper
http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf

“Their δ ¹³ CPDB of −24 ± 5‰ is consistent with a biogenic origin”

Even though I’ve been expecting life on Earth to be that old or older, I’d still like to know more about why they think that this carbon isotope fractionation is due to biological fixing of carbon rather than due to inorganic chemistry.

It’s particularly important that the date of 4.1 Ga is earlier than the bulk of the “late heavy bombardment”. “The Late Heavy Bombardment occurred approximately 4.1 to 3.8 Ga ago. It’s been repeatedly claimed recently that life on Earth couldn’t have survived the late heavy bombardment era, which I haven’t believed for a minute, because any part of this bombardment would have only affected part of the Earth at any one time, and life could have repeatedly regrown over the scars from survivors on the other side.

mollwollfumble said:

It’s particularly important that the date of 4.1 Ga is earlier than the bulk of the “late heavy bombardment”. “The Late Heavy Bombardment occurred approximately 4.1 to 3.8 Ga ago. It’s been repeatedly claimed recently that life on Earth couldn’t have survived the late heavy bombardment era, which I haven’t believed for a minute, because any part of this bombardment would have only affected part of the Earth at any one time, and life could have repeatedly regrown over the scars from survivors on the other side.

Depending on the bombardment, I believe atmospheric changes could theoretically prevent life. Isn’t that one of the theories about the demise of the dinosaurs, that an asteroid strike caused worldwide changes which the dinos couldn’t survive?

Divine Angel said:

mollwollfumble said:

It’s particularly important that the date of 4.1 Ga is earlier than the bulk of the “late heavy bombardment”. “The Late Heavy Bombardment occurred approximately 4.1 to 3.8 Ga ago. It’s been repeatedly claimed recently that life on Earth couldn’t have survived the late heavy bombardment era, which I haven’t believed for a minute, because any part of this bombardment would have only affected part of the Earth at any one time, and life could have repeatedly regrown over the scars from survivors on the other side.

Depending on the bombardment, I believe atmospheric changes could theoretically prevent life. Isn’t that one of the theories about the demise of the dinosaurs, that an asteroid strike caused worldwide changes which the dinos couldn’t survive?

Yes, but it didn’t wipe out life.

Divine Angel said:

mollwollfumble said:

It’s particularly important that the date of 4.1 Ga is earlier than the bulk of the “late heavy bombardment”. “The Late Heavy Bombardment occurred approximately 4.1 to 3.8 Ga ago. It’s been repeatedly claimed recently that life on Earth couldn’t have survived the late heavy bombardment era, which I haven’t believed for a minute, because any part of this bombardment would have only affected part of the Earth at any one time, and life could have repeatedly regrown over the scars from survivors on the other side.

Depending on the bombardment, I believe atmospheric changes could theoretically prevent life. Isn’t that one of the theories about the demise of the dinosaurs, that an asteroid strike caused worldwide changes which the dinos couldn’t survive?

Atmospheric conditions could never wipe out all life. Many lifeforms survive on Earth without ever coming in contact with the atmosphere. For example, bacteria live in deep oil wells, certain creatures survive packed in salt or under deep ice, tubeworms and hagfish live on the bottom of the ocean, tardigrades can survive for a while in outer space. Plant seeds can survive underground for long periods. Even some hibernating chordates can survive with minimal atmosphere for months.

Obviously, humans and dolphins can’t. Dinosaur eggs may have been able to survive without atmosphere, but not adult dinosaurs or marine reptiles.

Divine Angel said:

mollwollfumble said:

It’s particularly important that the date of 4.1 Ga is earlier than the bulk of the “late heavy bombardment”. “The Late Heavy Bombardment occurred approximately 4.1 to 3.8 Ga ago. It’s been repeatedly claimed recently that life on Earth couldn’t have survived the late heavy bombardment era, which I haven’t believed for a minute, because any part of this bombardment would have only affected part of the Earth at any one time, and life could have repeatedly regrown over the scars from survivors on the other side.

Depending on the bombardment, I believe atmospheric changes could theoretically prevent life. Isn’t that one of the theories about the demise of the dinosaurs, that an asteroid strike caused worldwide changes which the dinos couldn’t survive?

The last theory that I heard was that it was likely to be a combination of meteor impact and volcanic activity.. the Himalayas.

Ian said:

Divine Angel said:

mollwollfumble said:

It’s particularly important that the date of 4.1 Ga is earlier than the bulk of the “late heavy bombardment”. “The Late Heavy Bombardment occurred approximately 4.1 to 3.8 Ga ago. It’s been repeatedly claimed recently that life on Earth couldn’t have survived the late heavy bombardment era, which I haven’t believed for a minute, because any part of this bombardment would have only affected part of the Earth at any one time, and life could have repeatedly regrown over the scars from survivors on the other side.

Depending on the bombardment, I believe atmospheric changes could theoretically prevent life. Isn’t that one of the theories about the demise of the dinosaurs, that an asteroid strike caused worldwide changes which the dinos couldn’t survive?

The last theory that I heard was that it was likely to be a combination of meteor impact and volcanic activity.. the Himalayas.

Nearly right. A combination of meteor impact (Yucatan Peninsula) and volcanic activity (Deccan traps in India, further south than the Himalayas). The volcanic activity happened first.

mollwollfumble said:

Ian said:

Divine Angel said:

Depending on the bombardment, I believe atmospheric changes could theoretically prevent life. Isn’t that one of the theories about the demise of the dinosaurs, that an asteroid strike caused worldwide changes which the dinos couldn’t survive?

The last theory that I heard was that it was likely to be a combination of meteor impact and volcanic activity.. the Himalayas.

Nearly right. A combination of meteor impact (Yucatan Peninsula) and volcanic activity (Deccan traps in India, further south than the Himalayas). The volcanic activity happened first.

>>The release of volcanic gases, particularly sulfur dioxide, during the formation of the traps contributed to contemporary climate change. Data points to an average drop in temperature of 2 °C in this period.

Because of its magnitude, scientists formerly speculated that the gases released during the formation of the Deccan Traps played a role in the Cretaceous–Paleogene extinction event (also known as the K–Pg extinction), which included the extinction of the non-avian dinosaurs. Sudden cooling due to sulfurous volcanic gases released by the formation of the traps and localised gas concentrations may have contributed significantly to mass extinctions. However, the current consensus among the scientific community is that the extinction was triggered by the Chicxulub impact event in Central America (which would have produced a sunlight-blocking dust cloud that killed much of the plant life and reduced global temperature, called an impact winter).

Work published in 2014 by geologist Gerta Keller and others on the timing of the Deccan volcanism suggests the extinction may have been caused by both the volcanism and the impact event. This was followed by a similar study in 2015.<<

https://en.wikipedia.org/wiki/Deccan_Traps

I was going to say, “Yes, I had that idea as soon as I realised that every major extinction event other than the K-T was definitively caused by volcanic action”. But …

> The release of volcanic gases, particularly sulfur dioxide, during the formation of the traps contributed to contemporary climate change. Data points to an average drop in temperature of 2 °C in this period.

Once the atmospheric sulfur dioxide content hits 100 ppb I’m not going to care about a piddling thing like a 2 °C climate change, 250 ppb is worse and is not recommended for even short term exposure. A concentration of 20 ppm will cause immediate irritation of the nose, throat and eyes. I once checked back through ice core records on the web so see if the world SO ₂ concentration became high enough to be deadly at any time during the ice core records – it didn’t. And most importantly to me, that time period included the massive undersea volcanism event that led to a resurfacing of large parts of the Pacific Ocean. At that I breathed a sigh of relief, the world’s oceans do an exceptionally good job of absorbing SO ₂ released from undersea volcanism.

SO ₂ makes up about 10% of all the gases released from volcanoes. The rest is almost all H ₂ O and CO ₂.

I probably should put this here. (Note, the web-title is misleading.)

This report indicates that the dating of the Late Heavy Bombardment could well be dodgy. It was assumed that ex-situ shocked zircons collected from the moon showed a date-reset from the Late Heavy Bombardment.

Ex-situ shocked zircons collected from the 300 km-wide, 2 billion year old Vredefort impact structure (South Africa) do not show reset dates. They show the date of the impacted rocks’ formation from magma. This cast doubt on Late Heavy Bombardment dates.

http://www.abc.net.au/news/2015-10-28/zircon-study-questions-method-used-to-help-date-life-on-earth/6890122