Ancient Tides and Life Origination

[Airbrush]

If the moon was so close to the earth Billions of years ago when life originated, and the moon was whizzing around the earth several times per (24-hour) day, how could life originate in the midst of such violent tides that were a THOUSAND times higher than they are today? Huge tsunamis over a mile high would rush in and out several times per day.

[Mokele]

What makes you think it was so close? Or so fast? Or that life originated on the coast rather than around deep-sea vents?

[Airbrush]

I tried to find a reference for you, but failed. It is common knowledge the moon is moving away from the earth an inch or two per year. A Billion years ago it was much closer. There was a History Channel program which stated ancient tides were a THOUSAND times greater than they are now, and that the moon was orbiting the earth much faster and closer than it is today.

 

Life probably did not originate around deep-sea vents, but rather originated in much milder, nutrient rich tidal pools, then some species migrated to the deep-sea vents to evolve.

[Mokele]

Looks like the History channel was wrong, as usual:

 

http://www.nature.com/nature/journal/v320/n6063/abs/320600a0.html

 

Basically, the rate of change of Earth-Moon distance is not constant - the moon's position was much more stable initially. Currently, the moon is ~60 Earth-radii away, while 2.5 billion years ago, it was ~52. Closer, but nowhere near close enough to cause the effects you suggest.

 

Life probably did not originate around deep-sea vents, but rather originated in much milder, nutrient rich tidal pools, then some species migrated to the deep-sea vents to evolve.

 

Actually, there is a strong possibility, newly suggested in the abiogenesis community, that life *did* originate around thermal vents. We don't (and probably can't) know for sure, but it's a very real possibility.

[Airbrush]

That is interesting info Mokele. That was a question that has bothered me a long time.

 

The possibility of life originating around geo-thermal vents is also interesting. I always supposed the deep ocean conditions were too extreme for life to originate, and that life had to originate in very favorable mild conditions. Then it could migrate and adapt to extreme conditions. But deep ocean vents may be even more stable and not upset by drastic changes on the surface.

[D H]

Looks like the History channel was wrong, as usual:

http://www.nature.com/nature/journal/v320/n6063/abs/320600a0.html

That is a 22 year old article you cited, Mokele. In this case it is the Nature article that is wrong, not the History Channel. The History Channel is merely reciting the currently favored hypothesis regarding the origin of the Moon -- the Giant Impact Hypothesis. In a nutshell, a large Mars-sized body collided with the recently-formed Earth about 4.5 billion years ago. The iron core of this body fell into the Earth while the mantle material rebounded into orbit. The Moon quickly coalesced from this ejected mantle material. The angular momentum inparted by the collision made the post-collision Earth day a mere 5 hours long. The Moon was a lot closer (a whole lot closer) to the Earth than it is now. Since tidal forces are inversely proportional to the cube of distance, a factor of 10 reduction in the Earth-Moon distance would yield tides 1000 times higher than present.

 

Unlikely as it seems, this hypothesis is a lot less far-fetched than any other explanation. It explains lots of wierd characteristics of the Earth and the Moon: the Earth's rather large and the Moon's rather small iron cores; the common oxygen isotope ratios on the Earth and Moon; and the presence of potassium, rare earths, and phosphorus in some lunar rocks (google KREEP) that suggest the Moon was once largely molten.

 

References (just a few; google "Giant Impact Hypothesis" for more):

http://www.nature.com/nature/journal/v412/n6848/full/412708a0.html

http://www.nature.com/nature/journal/v437/n7063/full/nature04129.html

http://physicsworld.com/cws/article/news/17802

http://arxiv.org/abs/astro-ph/0405372

 

 

Life probably did not originate around deep-sea vents, but rather originated in much milder, nutrient rich tidal pools, then some species migrated to the deep-sea vents to evolve.

In this case, Mokele is reciting the currently favored hypothesis regarding the formation of life. Moreover, those huge tides in primordial times may well have helped life along rather than having hindered it.

 

More references:

http:// http://hal.archives-ouvertes.fr/docs/00/33/03/10/PDF/bg-2-97-2005.pdf

http://arxiv.org/abs/astro-ph/0112399

[Mokele]

The angular momentum inparted by the collision made the post-collision Earth day a mere 5 hours long. The Moon was a lot closer (a whole lot closer) to the Earth than it is now. Since tidal forces are inversely proportional to the cube of distance, a factor of 10 reduction in the Earth-Moon distance would yield tides 1000 times higher than present.

 

Ahh. I knew about the Giant Impact hypothesis, but didn't know things had been that extreme.

 

Would conditions have be as extreme almost a billion years later, when life arose? What little I know of the physics of these sorts of things leads me to suspect there wouldn't be a simple linear trend over time.

 

Mokele

[Airbrush]

I'm glad to hear you say that DH. Then about a Billion years ago huge tsunamis hundreds of meters high would be the ocean norm. Tidal pools, with mild, nutrient-rich conditions would form all around the limits of tidal advance.

[D H]

Whoa, whoa, whoa! Do not extrapolate on top of something that is already just a hypothesis. One billion years represents about 2/9 of the age of the Earth. The Moon moved from wherever it formed (and we do not know that) to where it is today over a period of 4.5 billion years. Well over 7/9 of that migration occurred during the first 7/9 of that 4.5 billion years because, as Mokele noted, the tidal recession of the Moon is not linear. Not even close. As I noted, tidal forces are inversely proportional to the cube of the separation distance.

[Ophiolite]

Since the largest tides would have occured while the Earth was still actively accreting it makes for some interesting mental pictures. 4.2 b.y. ago, for example, impacts large enough to completely evaporate the oceans and melt a significant portion of the crust would have been commonplace.

So now instead of an ocean of water subject to massive tidal forces, we have a sea of lava subject to the same forces. I rather like the idea of a 150m lava tsunami rolling up a primeval beach. Not very good as an environment for abiogenesis, but it would look great in cgi.

[npts2020]

That is interesting info Mokele. That was a question that has bothered me a long time.

 

The possibility of life originating around geo-thermal vents is also interesting. I always supposed the deep ocean conditions were too extreme for life to originate, and that life had to originate in very favorable mild conditions. Then it could migrate and adapt to extreme conditions. But deep ocean vents may be even more stable and not upset by drastic changes on the surface.

 

The part I put in bold is only a matter of perspective. To an archaeon born in an deep-sea ocean vent, eating sulphur to survive, where you live and thrive is probably as extreme as the environment on the side of the moon facing the sun would be to you. IMO life forms that could withstand what we would consider to be extreme conditions should have been the first to evolve.

[Sisyphus]

The part I put in bold is only a matter of perspective. To an archaeon born in an deep-sea ocean vent, eating sulphur to survive, where you live and thrive is probably as extreme as the environment on the side of the moon facing the sun would be to you. IMO life forms that could withstand what we would consider to be extreme conditions should have been the first to evolve.

 

I agree, actually. When you think about it, an ocean vent is actually kind of an ideal cradle for life: warm, nutrient-rich, muddy water well-protected from the interruptions of surface events. What more could a fragile self-replicating pattern ask for? Don't let the fact that it's so hostile to us trick us into thinking of it as hostile, period. Moving back in with your parents is usually pretty rough...

[Airbrush]

Whoa, whoa, whoa! Do not extrapolate on top of something that is already just a hypothesis. One billion years represents about 2/9 of the age of the Earth. The Moon moved from wherever it formed (and we do not know that) to where it is today over a period of 4.5 billion years. Well over 7/9 of that migration occurred during the first 7/9 of that 4.5 billion years because, as Mokele noted, the tidal recession of the Moon is not linear. Not even close. As I noted, tidal forces are inversely proportional to the cube of the separation distance.

 

That is fascinating! So that means that about a Billion years ago the surface of the ocean was probably not a wild boiling cauldron of constant half-mile high mega-tsunamics crashing onto all the earth's coastline. By a Billion years ago the oceans had settled down to be rather sedate. The moon's orbit around the earth was (about what?) less than 2 orbits in a 24-hour period? And tides were only a few times higher than they are today?

 

As the other poster noted that would be quite a sight to see the very early earth of boiling molten rock tsunamics several miles high, caused by intense tidal action, along with the bombardment of meteors and comets, as a constant condition for millions of years! Such extreme conditions are beyond imagining.