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View Full Version : Early Earth Wasn't So Hellish



Fraser
2005-Nov-18, 08:14 PM
SUMMARY: Most geologists believe that the early history of our planet was an extreme, "hellish" environment, under constant bombardment from asteroids, and completely devoid of modern formations, like continents. Researchers from ANU disagree, and think they've found evidence that continents had already formed within the first 500 million years, and there was liquid water interacting with rocks. The Earth at that time might have looked remarkably similar to our current planet, complete with continents and oceans.

View full article (http://www.universetoday.com/am/publish/anu_hadean_earth.html)
What do you think about this story? post your comments below.

qraal
2005-Nov-19, 06:24 AM
Hi Fraser

The early Earth still wasn't healthy for current lifeforms - current temperature estimates are ~ +90 degrees C (+194 F) and an interesting atmospheric mix of CO2 and H2, with a bit of N2 and very little oxygen. That's based on the likely mantle chemistry that volcanism was spewing volatiles from.

Eventually the H2 was replaced by CH4 and more N2. Oxygen remained below current levels until sometime after ~ 450 million years ago. Even in the early Cambrian O2 was only 6% and CO2 somewhere close to ~ 5%. During the Carboniferous the O2 climbed to 35%, but came crashing down to ~ 10% at the time of the dinosaurs.

So Earth was friendly to "life" but it was nasty to human and animal life for a long, long time.

Adam

SolusLupus
2005-Nov-19, 06:36 AM
That makes me wonder, though. Could bacteria still evolve in an environment that just happens to be "hellish" to human and animal life?

i mean, in the book Nightfall, a species evolved in a setting that was very hot, with, like, 4 suns.

qraal
2005-Nov-19, 07:45 AM
Hi

Bacteria are damned hardy and the conditions invoked for making amino acids and short-chain organics are usually pretty hot too. Hyper-thermophiles (bugs that actually grow at +90) typically come out as basal in tree-of-life analyses of highly conserved protein sequences, so the odds are good that life started in a heat bath.

Adam

cran
2005-Nov-19, 08:29 AM
That makes me wonder, though. Could bacteria still evolve in an environment that just happens to be "hellish" to human and animal life?

i mean, in the book Nightfall, a species evolved in a setting that was very hot, with, like, 4 suns. Yes, and they still do ... we call them 'extremophiles' ...

graal, I'm curious as to where you get those figures quoted ...

Earlier this year, in discussions and correspondence with Simon Wilde (he is one of my professors at Curtin Uni, and the discoverer of the oldest Jack Hills zircon (4.4+ Gy) - on which most of these studies are based), the crystallisation of that particular piece of zircon (which is a fragment within a younger crystal - a mere babe at 3+ Gy) had to occur in less than 780degC in a near-surface 'terrestrial' magma. Estimates of surface temperatures and pressures at that time were 180-300 degC and 230-270 atm - this means that water was not literally a liquid; it was a supercritical fluid - a state of matter which has some properties of a liquid (eg density) and some properties of a gas (eg molecular activity) ...

so, yes - still pretty 'hellish' from our point of view. :evil:

George
2005-Nov-19, 06:29 PM
And what about the ocean floor life forms nourished by volcanic vents? Is there much anerobic life there? Would this be a possible birth place back then?

cran
2005-Nov-19, 07:02 PM
And what about the ocean floor life forms nourished by volcanic vents? Is there much anerobic life there? Would this be a possible birth place back then? It's one of the contenders, certainly ... evidence for life in the Hadean is extremely limited, and still being debated, as far as I know.

George
2005-Nov-21, 02:58 PM
It's one of the contenders, certainly ... evidence for life in the Hadean is extremely limited, and still being debated, as far as I know.

I like what Charles Darwin's grandpa composed:

Organic life beneath the shoreless waves
Was born and nurs'd in ocean's pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the watery mass;
These, as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring,
And breathing realms of fin and feet and wing.
Erasmus Darwin. The Temple of Nature. 1802

Having water early in our history is a great asset.

cran
2005-Nov-21, 03:36 PM
Erasmus Darwin. The Temple of Nature. 1802 That's pretty insightful for 1802, George ... as a literate, Erasmus may well have been aware of Hutton's view of uniformitarianism (published in 1785), as well as the Neptunists' school of thought, but faunal succession (which leads logically to evolution) wasn't really accepted until Cuvier published in ~1817.
So, it seems that not all advances are sudden inspirations which occur in isolation.
Thanks for that. :)

George
2005-Nov-22, 01:18 AM
That's pretty insightful for 1802, George ... as a literate, Erasmus may well have been aware of Hutton's view of uniformitarianism (published in 1785), as well as the Neptunists' school of thought, but faunal succession (which leads logically to evolution) wasn't really accepted until Cuvier published in ~1817.
So, it seems that not all advances are sudden inspirations which occur in isolation.
Thanks for that. :)

Your welcome. Evolution itself is following it's own plan. ;)

Erasmus seems to have been quite prominent. IIRC, he turned down an offer to become the Kings doctor. He was an inventor. No doubt, Darwin, as myself, are influenced by our granddads. :) Albeit, Darwin's main elements were not found in Erasmus evolution views; branching and natural selection.

No doubt Hutton and Smith were highly influential on Lyell's lengthy geological processes. Darwin was highly influenced by Lyell's Principles of Geology, and William Palley's Natural Theology; memorizing much of the latter, surprisingly. [I could be off a little as I am just now beginning my study of evolution.]

SolusLupus
2005-Nov-22, 03:29 AM
Evolution has a plan?

wayneee
2005-Nov-22, 03:57 AM
That makes me wonder, though. Could bacteria still evolve in an environment that just happens to be "hellish" to human and animal life?

i mean, in the book Nightfall, a species evolved in a setting that was very hot, with, like, 4 suns.
Azimov's Nightfall? I was unaware that the temperature was high on that world. The Four Suns , I thought were there to show what a race grown in the light would do if suddenly faced with the prospect of darkness.
But any way , yes Bacteria have been found on volcanic vents underwater, even life http://www.ovpr.uga.edu/researchnews/92sp/boiling.html

SolusLupus
2005-Nov-22, 03:59 AM
I'm pretty sure it was hot on that planet. Not sure HOW hot, but pretty darn hot. In fact, when they talked about the idea of a planet having one sun (in the book, not the short story), one said, "But wouldn't they freeze to death?"

cran
2005-Nov-22, 05:05 AM
If the original reference was to Asimov's Nightfall, then the climate regime was inferred rather than directly explained (as Lonewulf just pointed out) - but I think it was 6 suns ... the system was set near the centre of the galaxy ... there's a reference to the location right at the end of the story ... comparing their view of the sky during the exceedingly rare 6-sun eclipse, with our 'mere' 2500 odd 'naked-eye' stars ... the story explored latent cultural phobias (how would you if you were afraid of the dark in a world that never gets dark?) ...
[part of that concept was explored in Pitch Black... ] and what would happen to civilisation in the face of an unexpected (or unbelieved) event.

SolusLupus
2005-Nov-22, 03:14 PM
I didn't agree with the majority of what Asimov thought would happen, though. The whole "murder by a 10 year old girl" was just... stupid. The burning buildings to make light, though, I would understand; just not the whole "WE CRAZY! WE KILL YOU!" thing

cran
2005-Nov-22, 03:37 PM
Poor Isaac, for all his brilliance, he did occasionally wander off the beam ... but then, amongst his peers, who didn't?

George
2005-Nov-22, 04:42 PM
Evolution has a plan?
Oops. How about: "Evolution ideas are branching out in accordance with evolutionary-like patterns"? :) [There is bound to be someone who has caught the essence in a more clever phrase. Mine lacks brevity. Darwin admitted he did not like his term "natural selection" but for the sake of brevity.]