Friday, October 23, 2015

Zircons and Earth's First Life

Bits of carbon encased in zircon crystals more than four billion years ago may have come from living creatures.

Then again, maybe not. Either way, we're learning more about Earth's long story.
  1. Zircons and Life's Dawn
  2. Jack Hills Zircons Revisited

Faith - - -



(From Efbrazil, via Wikimedia Commons, used w/o permission.)
(This universe, so far: 13,800,000,000 years mapped onto a 12-month calendar.)

We've learned quite a bit in the centuries since in 1 Samuel 2:8 and Psalms 148:4 were written.

I'm confident that God could have made a universe that looked like Mesopotamian cosmology: but that's not what it's like.

This space-time continuum doesn't work like Anaximander's model, either. Anaximander's cosmology had Earth in the center: but he speculated that we might not be standing on the only world, and that worlds change.

Aristotle's cosmology had Earth in the center of the universe, too. He didn't think multiple worlds existed, though.

About 16 centuries later, educated Europeans like Dante Alighieri had a very high opinion of Aristotle. Some may even have had the attitude expressed by Dante, that Aristotle was "the Master ... of those who know."

Meanwhile, some academics said that other worlds might exist. Aristotle's fan base insisted there was only one: because Aristotle said so.

Arguments got heated, so in 1277 the Church stepped in. Some of the 219 points have been rescinded since then, but as far as I know, 27/219 still holds: God's God, Aristotle's not. If the Almighty decides that the visible creation has multiple worlds — that's the way it is.

I've discussed Job 9:6-7, international long-distance telephone service, and extraterrestrial life, before. (August 7, 2015; July 31, 2015; October 10, 2014; February 23, 2014)

- - - Reason, and Truth


If you've read my 'science' posts before, you probably know that I think the universe is billions, not thousands, of years old; Earth isn't flat; Adam and Eve aren't German; poetry isn't science; and thinking is not a sin.

You probably know why I think truth is important, too, so go ahead: skip down to Zircons and Life's Dawn, take a coffee break, go for a walk, or whatever strikes your fancy.

We're born with a thirst for truth.

The search for truth leads ultimately to God — but I don't see a point in ignoring the wonders and beauty of this creation. Besides, scientific discoveries are invitations "...to even greater admiration for the greatness of the Creator...." (Catechism, 27, 283)

I don't see a problem with studying this universe, because I think God makes it. If we discover something that doesn't fit our preconceived notions: that's out problem, not God's. (Genesis 1:1-31; Catechism, 159, 301)

It's like Pope Leo XIII wrote:
"...God, the Creator and Ruler of all things, is also the Author of the Scriptures - and that therefore nothing can be proved either by physical science or archaeology which can really contradict the Scriptures. ... Even if the difficulty is after all not cleared up and the discrepancy seems to remain, the contest must not be abandoned; truth cannot contradict truth...."
("Providentissimus Deus,"1 Pope Leo XIII (November 18, 1893) [emphasis mine])
From a Catholic viewpoint, faith is "a personal adherence of man to God." It's also "...a free assent to the whole truth that God has revealed...." (Catechism of the Catholic Church, 150)

Faith isn't blind, or stupid. It's not supposed to be, at least.
"1 Beloved, do not trust every spirit but test the spirits to see whether they belong to God, because many false prophets have gone out into the world.

"This is how you can know the Spirit of God: every spirit that acknowledges Jesus Christ come in the flesh be longs to God,

"and every spirit that does not acknowledge Jesus 2 does not belong to God. This is the spirit of the antichrist that, as you heard, is to come, but in fact is already in the world."
(1 John 4:1-3)

"Man's faculties make him capable of coming to a knowledge of the existence of a personal God. But for man to be able to enter into real intimacy with him, God willed both to reveal himself to man and to give him the grace of being able to welcome this revelation in faith. The proofs of God's existence, however, can predispose one to faith and help one to see that faith is not opposed to reason."
(Catechism, 35)
I add another post to my faith and reason, science and religion link list almost every Friday. Cultural quirks and conflicts of the last couple centuries notwithstanding, it's science and religion, faith and reason. (Catechism, 36, 286, 355-373, 2293)

Goodbye, Hadean Eon?


A supereon is the largest unit of geologic time; a supereon is divided into eons; eons eras; eras into periods, epochs and ages. None of that will help you avoid traffic jams or avoid ring around the collar, but I think stuff like this is fascinating. Your experience may vary.

Nobody talked about the Hadean eon before 1972, because that's when geologist Preson Cloud first used the term. The Hadean is named after Hades, since scientists figured Earth was a hellish place back then — from the time Earth formed to 4,000,000,000 years ago.

It still looks like Earth was a profoundly inhospitable place for life right after it formed. On the other hand, bits of carbon sealed in zircon crystals probably came from living critters.

The crystals are well over four billion years old: which means we have more to learn about Earth's early eras.


1. Zircons and Life's Dawn



(From Elizabeth A. Bell, Patrick Boehnke, T. Mark Harrison, Wendy L. Mao, via PNAS, used w/o permission.)
("Transmission X-ray image of RSES 61-18.8...."
(Elizabeth A. Bell, Patrick Boehnke, T. Mark Harrison, Wendy L. Mao)
"Ancient crystal suggests life on Earth appeared 4.1 billion years ago"
Richard Valdmanis, Reuters (October 19, 2015)

"An ancient zircon crystal unearthed in Western Australia may hold evidence that life appeared on the planet 4.1 billion years ago, or about 300 million years earlier than previously thought, according to a team of U.S. researchers.

"Scientists from Stanford University and the University of California, Los Angeles said they recently collected some 10,000 multibillion year-old zircons in Jack Hills, Australia, including one believed to contain a carbon deposit that is 4.1 billion years old, give or take 10 million years....

"...Scientists have used the fossil record to assert that the history of life on Earth began about 3.8 billion years ago, in the form of single-celled creatures. Humans are believed to have first appeared on Earth only about 200,000 years ago...."
About that last paragraph. We've found microfossils in the Greenstone Belt, very old exposed rock in South Africa, that are about 3,500,000,000 years old. Graphite found in western Greenland that probably came from the carbon in living critters is about 3,700,000,000 years old.

Here's what scientists who worked with these zircons said:
"...Life on Earth is an ancient phenomenon, with the earliest identified microfossils at nearly 3.5 billion years before present (Ga) (1) and the earliest potential chemofossils at 3.83 Ga(2, 3)...."
("Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon," Elizabeth A. Bell et al. | references to (1) "The oldest records of photosynthesis," Awramik SM, Photosynth Res 33:75-89 (1992) and (2) "Evidence for life on Earth before 3,800 million years ago," Mojzsis SJ, et al., Nature 384(6604):55–59 (1996)
The Reuter article's "...humans are believed..." is fairly accurate — provided you consider anatomically modern humans as "human" and everybody else as "not human." I don't, and I've been over that before. A lot. (September 18, 2015; September 11, 2015; July 11, 2014)

If the carbon in these zircons came from living critters, that means life started on Earth before the late heavy bombardment (LHB) — and survived that cataclysm, or started again, almost immediately after it stopped raining asteroids.

Or maybe the late heavy bombardment didn't happen. The last I checked, scientists were still undecided on whether the LHB is real, or a misinterpretation of data. (July 31, 2015)

Rethinking the Hadean


Zircon, ZrSiO4, is hard, durable, and chemically inert.

When this particular zircon crystal, RSES 61-18.8, formed, it encased tiny bits of carbon. For the next 4,100,000,000-odd years, RSES 61-18.8 remained intact: preserving the carbon.

What makes this carbon special is that it's "isotopically light:" δ13C, or Carbon-13. Isotopes are elements with an unusual number of neutrons. Carbon-13 can come from non-living processes, but it's almost always produced by critters.

Finding carbon that was almost certainly part of something living more than four billion years ago is a big deal, at least for some scientists:
"...Scientists had long believed the Earth was dry and desolate during that time period. Harrison's research — including a 2008 study in Nature he co-authored with Craig Manning, a professor of geology and geochemistry at UCLA, and former UCLA graduate student Michelle Hopkins — is proving otherwise.

" 'The early Earth certainly wasn't a hellish, dry, boiling planet; we see absolutely no evidence for that,' Harrison said. 'The planet was probably much more like it is today than previously thought.'..."
("Life on Earth likely started at least 4.1 billion years ago — much earlier than scientists had thought," UCLA Newsroom)
It's starting to look like life started even earlier than scientists thought. If that's true, we may have to re-name the Hadean eon — or, more likely, revise the geologic time scale again.

That's been going on since the late 18th century, when Abraham Gottlob Werner and others started talking about Urgebirge, Übergangsgebirge, Flötz, and Aufgeschwemmte series. I've mentioned Nicolas Steno and stratiography before. (May 1, 2015)

These scientists — not Werner and company: the PNAS paper's bunch; Bell, Boehnke, Harrison, and Mao — used confocal Raman spectroscopy with a green laser to study the carbon without disturbing the surrounding zircon crystal.

Raman spectroscopy uses inelastic scattering, is named after Chandrasekhara Venkata Raman, and has nothing to do with noodle soup.

More that you probably need, or want, to know about these old zircons:

2. Jack Hills Zircons Revisited



(From Robert Simmon, NASA; NASA Earth Observatory; used w/o permission.)
"Diamonds hint at 'earliest life' "
Jonathan Fildes, BBC News (July 2, 2008)

"Tiny slivers of diamond forged on an infant Earth may contain the earliest traces of life, a study has shown.

"Analysis of the crystals showed they contain a form of carbon often associated with plants and bacteria.

"The rare gems were found inside zircon crystals, formed a few hundred million years after the Earth came into being.

"Writing in the journal Nature, the researchers caution that their results are not definitive proof of early life but do 'not exclude' the possibility.

" 'We're all a little sceptical,' said Dr Martin Whitehouse of the Swedish Museum of Natural History and one of the authors of the paper.

"If the carbon was derived from primitive organisms, it would push back the date for life appearing on Earth by around 500 million years, to beyond 4.25 billion years ago. The Earth itself is just 4.6 billion years old...."
More nitpicking — Scientists are quite sure that Earth is 4,540,000,000 years old, plus or minus 50,000,000. That's pretty close to "4.6 billion," though.

"Dr. Martin Whitehouse," "zircon," and "Jack Hills," gave me enough to find the paper discussing "tiny slivers of diamond:"
The zircon grains those scientists studied were up to 4,252,000,000 years old — and again, the scientists couldn't be absolutely sure that the carbon-13 came from critters. But, as the BBC article said, they couldn't be sure that it wasn't, either.

Recognizing the limits of data and analysis is the sort of healthy skepticism that keeps scientists from jumping off the edge of reality: with occasionally-spectacular exceptions.

I've talked about Boule's Neanderthal, Hawkin's "grim Monsters," H. P. Lovecraft, and SETI, before. Fairly often. (September 11, 2015; July 24, 2015; November 21, 2014; June 27, 2014)

We've learned a lot since I was in high school.

Neuroscientists are learning how our brains are rewired by experiences, astronomers determined how fast this universe is using energy, other scientists are developing mathematical models for continua other than the space-time we're in, and that's another topic. Topics. (August 14, 2015; March 27, 2015; September 26, 2014)

Like I keep saying, there's more to learn:

2 comments:

Brigid said...

Something missing here: "Some may even had the attitude expressed by Dante, that"

The Friendly Neighborhood Proofreader

Brian Gill said...

Oops. Quite right. Fixed. Thanks, Brigid!

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