Life and the Goldilocks Planet

[Badly Shaved Monkey]

Does anyone know what conditions would be on Earth if the geosystem did not have the large-scale tempering influence of life? Would it runaway to Venus or Mars-like conditions, or would it stay equable for life on its surface?

 

[Asolepius]

Without life it would never have got to its present state. An oxidising atmosphere is normally unsustainable. If life stopped now, Earth would revert to a reducing atmosphere. It has been said that oxygen was a waste product of early life, and actually poisonous to many primitive organisms.

 

[HeyLeroy]

Terraforming Mars

I'm not sure if that's off-topic or not, but it's the first thing I thought of. Damn free-associating brain of mine!

More.

 

[H'ethetheth]

As far as I understand, it would probably still be comparable to the way it was 3.5 billion years ago. A carbon dioxide atmosphere and lots of liquid water on the surface causing plate tectonics. However I do recall hearing that the sun puts out something like 25% more energy these days than back then, so it might have reached a different state of equilibrium, or even run away by now.

 

[robinson]

Does anyone know what conditions would be on Earth if the geosystem did not have the large-scale tempering influence of life? Would it runaway to Venus or Mars-like conditions, or would it stay equable for life on its surface?

Nobody really knows. But with new discoveries about life, and the extreme conditions in which it does thrive, it seems there might be life no matter what condition the planet is in.

 

[Badly Shaved Monkey]

"Without life it would never have got to its present state"

That's a fair point, to which I can only respond, "D'oh". Didn't think the question through properly. Of, course the oxygen-rich atmosphere would not persist without life.

To slightly shift the terms of reference, if we release sufficient (I'll leave others to argue over the amounts!) CO2 etc, could we shift the Earth to a Venus-like state or does our position in the Solar System preclude such an extreme outcome?

 

[Dancing David]

"Without life it would never have got to its present state"

That's a fair point, to which I can only respond, "D'oh". Didn't think the question through properly. Of, course the oxygen-rich atmosphere would not persist without life.

To slightly shift the terms of reference, if we release sufficient (I'll leave others to argue over the amounts!) CO2 etc, could we shift the Earth to a Venus-like state or does our position in the Solar System preclude such an extreme outcome?

That depends, a lot of our earth's climate is moderated by the oceans. then there is the whole clouds versus dust thing. Some models say that just a couple messy volcanoes could lower the temperature. Some models show that if temperatures rise the we may enter an interglacial period, or we may have an ice age. That depends on how much moisture falls on the higher latitudes.

I don't think that we would approach Venus unless we really tried to, just a guess.

 

[Myriad]

The only way we could create Venus-like conditions on earth is by taking most of the organic molecules on the planet, converting all their carbon into carbon dioxide by reacting them with oxygen at high temperatures, and pumping it into the atmosphere.

Hey, wait...



Best,
Myriad

 

[Iamme]

I have preached on the wonders of the earth as to whether or not it is all just some lucky coincidence that earth has all that it does which has allowed us to enjoy life to the degree we can and do, that goes well beyond existing. I watched a tv show the other night on the earth and it's reversing magnetic field over the eons of time.(They claim we may be due for another reversal) And they said how the earth is like a (force field) in guarding us against space radiation. MORE "luck", eh? And how about more luck; that the atmosphere, with it's myriad of gases yield clear air. Perfectly clear. It is quite amazing to me that all this just happened...one lucky thing after the next. I got on this thinking again today when watching this guy wash his car using a flexible hose and nozzle at the end, in his paved driveway in front of his beautiful home, washing this nice metal and plastic and glass and rubber and copper wiring and (on and on) car that runs on this stuff they suck out of the ground.

 

[Badly Shaved Monkey]

it's reversing magnetic field over the eons of time.(They claim we may be due for another reversal)

Come the day, I shall be just laughing myself silly at all those smugly confused pigeons flying in all directions.

I know its petty, but there has to be revenge for all that excrement.

 

[Dancing David]

I have preached on the wonders of the earth as to whether or not it is all just some lucky coincidence that earth has all that it does which has allowed us to enjoy life to the degree we can and do, that goes well beyond existing. I watched a tv show the other night on the earth and it's reversing magnetic field over the eons of time.(They claim we may be due for another reversal) And they said how the earth is like a (force field) in guarding us against space radiation. MORE "luck", eh? And how about more luck; that the atmosphere, with it's myriad of gases yield clear air. Perfectly clear. It is quite amazing to me that all this just happened...one lucky thing after the next. I got on this thinking again today when watching this guy wash his car using a flexible hose and nozzle at the end, in his paved driveway in front of his beautiful home, washing this nice metal and plastic and glass and rubber and copper wiring and (on and on) car that runs on this stuff they suck out of the ground.

The real wonder is that guy in the shabby coat offering to wash his windshield for a buck with a grimy rag.

 

[DavidS]

As far as I understand, it would probably still be comparable to the way it was 3.5 billion years ago. A carbon dioxide atmosphere... ...However I do recall hearing that the sun puts out something like 25% more energy these days than back then, so it might have reached a different state of equilibrium, or even run away by now.

<shrug> No bones to pick there, at least not without doing more research than I'd like.

... and lots of liquid water on the surface causing plate tectonics.

I *would* be interested in an explanation linking water -- liquid, surface, or other primarily aqueous phase -- to the cause of plate tectonics.

I've been led to believe plate tectonics is caused by convection currents in the earth's mantle, where nearly water-free "rock" at very high temperatures and pressures flows like a viscous fluid. That is, plate tectonics would occur essentially the same if Earth were water-free.

My belief may be a bit entrenched, considering that other predictions derived from that model, its supporting evidence, and other evidence of the same genre have been putting beans on my table for many years. I'm not personally a geologist nor geophysicist, but I work closely with both; they assure me this is true, and they've established a record of being right about most big-picture stuff.

The only way we could create Venus-like conditions on earth is by taking most of the organic molecules on the planet, converting all their carbon into carbon dioxide by reacting them with oxygen at high temperatures, and pumping it into the atmosphere.

I'm doing what I can

 

[Buckaroo]

Here's a good article on the subject:

http://www.nasa.gov/centers/ames/news/releases/2002/02_60AR.html

Regarding the oxygen issue, an interesting side-effect of persistent oxygen on a rocky planet is that it makes a really good indicator of the existence of life -- at least the kind that has similar metabolic processes to ours. Using ozone (which a nice, sharp absorption feature at around 9.6 microns) as a proxy, a space-based interferometer could in principle remotely detect life on planets outside the solar system by looking at their near-infrared spectrum.

Cool.

 

[H'ethetheth]

I *would* be interested in an explanation linking water -- liquid, surface, or other primarily aqueous phase -- to the cause of plate tectonics.

I've been led to believe plate tectonics is caused by convection currents in the earth's mantle, where nearly water-free "rock" at very high temperatures and pressures flows like a viscous fluid. That is, plate tectonics would occur essentially the same if Earth were water-free.

My belief may be a bit entrenched, considering that other predictions derived from that model, its supporting evidence, and other evidence of the same genre have been putting beans on my table for many years. I'm not personally a geologist nor geophysicist, but I work closely with both; they assure me this is true, and they've established a record of being right about most big-picture stuff.



I'm doing what I can

Without water, there is no difference between oceanic and continental crust. The fact that subduction occurs is because there is a difference in density between the two, which keeps the whole process going. Water is a key factor in this, if not the key.
Venus is a very good example of what happens without water. It has an active mantle but no plate tectonics, if I recall correctly.

This is my understanding of course, and I'm willing to be corrected.

 

[Cuddles]

Without water, there is no difference between oceanic and continental crust. The fact that subduction occurs is because there is a difference in density between the two, which keeps the whole process going. Water is a key factor in this, if not the key.
Venus is a very good example of what happens without water. It has an active mantle but no plate tectonics, if I recall correctly.

This is my understanding of course, and I'm willing to be corrected.

I believe there is also a lubrication effect from the water. Rather than rock rubbing against rock, the contact between oceanic and continental plates contains mostly loose sediment mixed with water, which allows it to slide much more easily.

 

[H'ethetheth]

I believe there is also a lubrication effect from the water. Rather than rock rubbing against rock, the contact between oceanic and continental plates contains mostly loose sediment mixed with water, which allows it to slide much more easily.

Im not sure the lubrication is that literal. As I understood, the water lubricates the process by lowering the melting point of the surrounding mantle rock, which then forms new continental crust and volcanoes and such.

 

[KingMerv00]

And how about more luck; that the atmosphere, with it's myriad of gases yield clear air. Perfectly clear. It is quite amazing to me that all this just happened...

By clear I suppose you mean transparent?

Evolution favored sight based on radiation that passes through the air. What good is sight that doesn't let you see?

Douglas Adams would like to speak with you about a puddle.

 

[DavidS]

Don't get me wrong, I'm fairly well convinced that life, at least complex sentient life like us (well, most of us), required both plate tectonics and water. Not just water, but temperature and pressure reasonably near its triple point (or at least not too far removed from ). I'm pretty well convinced that the stability of that temperature and pressure and the availability of water has been strongly influenced by the presence of life. I'm just not convinced that either water or life causes plate tectonic activity,

Without water, there is no difference between oceanic and continental crust.

Reallly? Basalt is wet granite?

The fact that subduction occurs is because there is a difference in density between the two, which keeps the whole process going.

No, that's why continental crust floats on top and isn't subducted at convergent plate boundaries. If that were the cause of subduction, it wouldn't occur at convergent oceanic plate boundaries, and we wouldn't have Japan and the Aleutians.

The density difference that partially drives subduction is a mineralogical phase change and density increase in the subducting plate, induced by the increasing temperatures and pressures. The heavy diving end of the plate contributes to dragging the rest behind it.

Water is a key factor in this, if not the key.

If by "this" you mean plate tectonics: That's not yet demonstrated. If by "this" you mean all manner of other vulcanism, then I concur that water dragged into the subduction zone along with oceanic plate contributes to separation of lighter and more fusible blobs (plutons, IIRC?) that rise up to make things like Honshu, Kodiak, Ranier, El Capitan....

Venus is a very good example of what happens without water. It has an active mantle but no plate tectonics, if I recall correctly.

The absence of both doesn't implicate one as cause of the other. You can't get from

~A * ~B (lack of water AND lack of plate tectonics)

to

A -> B (water causes plate tectonics)

nor

~A -> ~B (lack of water prevents plate tectonics)

Best you can do is

~(~A -> B) (lack of water does not cause plate tectonics)

If Venus has active plate tectonics but no liquid water, that would indicate water need not be the cause of plate tectonics. I'm not competent to address whether Venus has active plate tectonics.

I believe there is also a lubrication effect from the water. Rather than rock rubbing against rock, the contact between oceanic and continental plates contains mostly loose sediment mixed with water, which allows it to slide much more easily.

I won't dispute that point, except to suggest that contribution to effect is insufficient evidence of cause. Crankcase oil makes my car's engine run better, but that ain't what makes it run. (I'll forego the gratuitous BASF paraphrase)

 

[H'ethetheth]

[...]
I'm just not convinced that either water or life causes plate tectonic activity,
[...]
If that were the cause of subduction, it wouldn't occur at convergent oceanic plate boundaries, and we wouldn't have Japan and the Aleutians.

The density difference that partially drives subduction is a mineralogical phase change and density increase in the subducting plate, induced by the increasing temperatures and pressures. The heavy diving end of the plate contributes to dragging the rest behind it.

If by "this" you mean plate tectonics: That's not yet demonstrated.
[...]
If Venus has active plate tectonics but no liquid water, that would indicate water need not be the cause of plate tectonics. I'm not competent to address whether Venus has active plate tectonics.

I'm getting in over my head here, so I clearly have some reading to do.

Thanks.

 

[Badly Shaved Monkey]

I am also at risk of getting in over my head, but, on the subject of the climate models that people use...

Presumably they could 'switch off' the functions that relate to biological processes, which would be easier to organise than arranging for a Gamma Ray Burst to go off in our near vicinity and removal all life experimentally.

Can we hazard a guess at what the model would then do?