What if Earth formed under different conditions?

[FungusForge]

Hello Science Labs Science and Spaceflight guys! I'm wondering how different Earth might be under a couple different conditions.

First: What if Earth's orbit had a far more extreme difference in periapsis and apoapsis? Particularly if the periapsis and apoapsis were riding on either edge of the goldilocks zone.

Second: What if Earth had a surface pressure of 4 bar?

[K^2]

4 bar - depends on composition, but if it's similar to Earth's, it should be fine. Cloud cover might end up being denser, which means even warmer temperatures on the surface, but so long as life adapts to that form the start, I don't see a problem.

Eccentricity is a bigger concern. Instead of conventional seasons due to axis inclination, which are balanced between the two hemispheres, you are going to end up with sizable global temperature swings. All of the surface is going to drop bellow freezing near the aphelion and climate will turn very hot and very humid at perihelion. I'm pretty sure you can forget about land life under these conditions. But oceans should still remain habitable. Surface will probably bloom with algae every "summer", and that will provide sufficient nutrients for more complex life to winter in the depths.

Could be an interesting world, but with no land life and reduced biodiversity, odds of it harboring something intelligent are greatly reduced.

[Camacha]

28 minutes ago, FungusForge said:

Earth had a surface pressure of 4 bar?

It had. It is what made these possible.

[GeneralVeers]

28 minutes ago, FungusForge said:

First: What if Earth's orbit had a far more extreme difference in periapsis and apoapsis? Particularly if the periapsis and apoapsis were riding on either edge of the goldilocks zone.

Probably no major differences. The Earth already has fairly wide seasonal temperature swings, for entirely different reasons--the most important one being that its axis is a bit wonky. Other factors are minor by comparison, so minor that it's impossible to conclusively link cause to effect most of the time.

 

29 minutes ago, FungusForge said:

Second: What if Earth had a surface pressure of 4 bar?

Hard to say. In the real-world oceans, at 4 atmospheres' pressure, life in general does just fine. Scuba divers can survive comfortably at those pressures (a hundred feet down, your tank air and the air in your lungs is at 4 atmospheres), the only problem being when the diver surfaces and the pressure comes off. But on this theoretical Earth's surface, it's possible some chemical processes would be affected. Oxygen, for example, starts to become toxic at high pressure; ordinary air at five to six atmospheres (around 150 feet for a scuba diver) can cause oxygen toxicity. So on this Earth, the oxygen content might need to be lower for life forms such as ourselves to survive.

That's the only example I can think of right now, but it's enough to illustrate the idea that basic chemistry might differ in a few ways.

[Findthepin1]

Well, in the latter situation it'd probably be warmer and just about all life would probably be bigger. There might be more flying animals.

I don't know about the former situation. Earth probably wouldn't have a moon like the one it has, the tidal forces from the eccentric orbit would probably pull it away eventually. I can't simulate it in US2 because it is broken, but I digress. There are probably some articles on the net about eccentric Earthlike exoplanets. This would probably be similar to this.

TL;DR: Word count: 104, Probably count: 9, 8.7% percent of the words here are "probably". Probably.

Edited February 5, 2016 by Findthepin1

[fredinno]

1 hour ago, K^2 said:

4 bar - depends on composition, but if it's similar to Earth's, it should be fine. Cloud cover might end up being denser, which means even warmer temperatures on the surface, but so long as life adapts to that form the start, I don't see a problem.

Eccentricity is a bigger concern. Instead of conventional seasons due to axis inclination, which are balanced between the two hemispheres, you are going to end up with sizable global temperature swings. All of the surface is going to drop bellow freezing near the aphelion and climate will turn very hot and very humid at perihelion. I'm pretty sure you can forget about land life under these conditions. But oceans should still remain habitable. Surface will probably bloom with algae every "summer", and that will provide sufficient nutrients for more complex life to winter in the depths.

Could be an interesting world, but with no land life and reduced biodiversity, odds of it harboring something intelligent are greatly reduced.

It depends on the eccentricity. If it remains in the habitable zone, land life might still develop.

However, Earth right now is actually pretty close to the edge of the habitable zone, in 1 billion years complex life will die from overheating.

6 minutes ago, Findthepin1 said:

Well, in the latter situation it'd probably be warmer and just about all life would probably be bigger. There might be more flying animals.

I don't know about the former situation. Earth probably wouldn't have a moon like the one it has, the tidal forces from the eccentric orbit would probably pull it away eventually. I can't simulate it in US2 because it is broken, but I digress. There are probably some articles on the net about eccentric Earthlike exoplanets. This would probably be similar to this.

TL;DR: Word count: 104, Probably count: 9, 8.7% percent of the words here are "probably". Probably.

No they wouldn't. But it would be pretty bad for life, having such variable seasons, as life would have to be adapted to much greater temperature differences,

[Shpaget]

The, so called, goldilocks zone is rubbish concept in this context. Any life that potentially develops would find whatever the conditions may be to be optimal. A emerging sentient species would probably praise the allmighty creator for providing such a well balanced world that offers a nice warm period perfect for growth and reproduction and a longer cold period "just made for" hibernation.

[kerbiloid]

4 bar means pressure x 4 which means either temperature x 4, or air density x 4, or their intermediate combination.
Even if temperature is 1.3 greater than now (i.e. 100°C), the answer is obvious.
So, 4 bar means density x 4.

Earth atmosphere 80% consists of nitrogen released from protogenic ammonia.
It's released almost totally, so 4 bar means (400% - 80%)/(20%) = 16 times more oxygen in atmosphere.
Oxygen is made of volcanic CO2. This means 16 times more volcanic CO2 would be released.
Volcanic gases consist of H2O and CO2. H2O condensate we call "an ocean".

So, 4 bars mean 16 times more intensive vulcanic activity, 16 times greater greenhouse effect, irreversible heating and a nice second Venus instead of the Earth.

[FungusForge]

3 minutes ago, Shpaget said:

The, so called, goldilocks zone is rubbish concept in this context.

Correct me if I'm wrong, but last I heard the goldilocks zone is a particular area where liquid dihydrogen oxide (fancy speak for water) has the potential to naturally exist on a planet. Not where human-like life could comfortably live.

So in the context of my question, it should be applicable.

[Shpaget]

In your scenario it is likely that human like life would not evolve. The evolution would certainly take another path. Whatever life that may develop would find different conditions optimal, liquid water or no liquid water. Life does not necessarily need water. After all, we only have one tree of life to study.

[K^2]

3 hours ago, fredinno said:

It depends on the eccentricity. If it remains in the habitable zone, land life might still develop.

OP specifically mentioned going to the outer edge of the hab zone, and that means permafrost on any world without significant greenhouse effect. Combine that with going to inner edge on the other side of the swing, and I cannot imagine any life that would survive on land.

I should, perhaps, specify terrestrial life. But if we imagine life that's drastically different to our own, our definition of habitable zone might not be applicable either.

[magnemoe]

5 hours ago, Camacha said:

It had. It is what made these possible.

Interesting, most say it was just the high oxygen content, but higher pressure would help even more for large things to fly and some other has also claimed higher pressures.
High pressure makes flying far easier, 

Now high pressure also trap more heat so put earth outward and give us mars for moon. 

[magnemoe]

2 hours ago, kerbiloid said:

4 bar means pressure x 4 which means either temperature x 4, or air density x 4, or their intermediate combination.
Even if temperature is 1.3 greater than now (i.e. 100°C), the answer is obvious.
So, 4 bar means density x 4.

Earth atmosphere 80% consists of nitrogen released from protogenic ammonia.
It's released almost totally, so 4 bar means (400% - 80%)/(20%) = 16 times more oxygen in atmosphere.
Oxygen is made of volcanic CO2. This means 16 times more volcanic CO2 would be released.
Volcanic gases consist of H2O and CO2. H2O condensate we call "an ocean".

So, 4 bars mean 16 times more intensive vulcanic activity, 16 times greater greenhouse effect, irreversible heating and a nice second Venus instead of the Earth.

This I don't get, Oxygen content has changed plenty over time.
In http://pubs.acs.org/subscribe/archive/ci/30/i12/html/12learn.html claimed pressure was hight earlier. 
Yes denser atmosphere trap more heat its however far to Venus conditions.

With more eccentricity you would want more greenhouse effect. Note that non tropic areas has strong temperature differences because of axial tilt. 
Temprature changes would be larger, you would also push climate belts towards equator. 

[kerbiloid]

 

1 hour ago, magnemoe said:

This I don't get, Oxygen content has changed plenty over time.
In http://pubs.acs.org/subscribe/archive/ci/30/i12/html/12learn.html claimed pressure was hight earlier. 
Yes denser atmosphere trap more heat its however far to Venus conditions.

With more eccentricity you would want more greenhouse effect. Note that non tropic areas has strong temperature differences because of axial tilt. 
Temprature changes would be larger, you would also push climate belts towards equator. 

According to the book I've read about the Earth pre-history

( Say, original version of this book:

https://books.google.ru/books?id=QHbeAq8YeXoC&lpg=PA568&ots=72H1SoPUw9&dq=sorokhtin%20ushakov%20earth&hl=ru&pg=PA449#v=onepage&q=pressure&f=false

- sorry, the original is not in English),

the Earth atmospheric pressure change was much less dramatical than that site tells.

 

As you can see here, 5-6 bar were here only once and not for a long time, right after great vulcanic activity had stopped.
Also, this CO2 has been quickly absorbed into carbonates and so on.
While a billion years later (when presumably the FeO in the Earth core will decay under the pressure into Fe and O, oxygen concentration will catastrophically increase and kill all life on the Earth).

Btw, many of the species living 60 mln years ago are still alive and feel good: mammals, birds, reptiles, so that site's data looks absolutely fantastic.
None of the mammals can live in 1 bar today and 5 bars earlier.

But I have consulted right now with this book - and you're right that 5-6 bar of O is not enough to greenhouse the Earth.
The book tells, that greenhouse would be "if the pressure would be several dozens bars".

 

Edited February 5, 2016 by kerbiloid

[fredinno]

11 hours ago, Shpaget said:

The, so called, goldilocks zone is rubbish concept in this context. Any life that potentially develops would find whatever the conditions may be to be optimal. A emerging sentient species would probably praise the allmighty creator for providing such a well balanced world that offers a nice warm period perfect for growth and reproduction and a longer cold period "just made for" hibernation.

The "habitable zone" is the zone habitable for liquid water to exist on the surface (assuming you also have a atmosphere and magnetic field).

A slightly smaller Trojan Mars (Mars is 0.102x Earth Mass, and an object up to 10% of the parent body can become a Trojan of the parent body) with a large moon would be a smaller twin Earth.

10 hours ago, Shpaget said:

In your scenario it is likely that human like life would not evolve. The evolution would certainly take another path. Whatever life that may develop would find different conditions optimal, liquid water or no liquid water. Life does not necessarily need water. After all, we only have one tree of life to study.

We only have evidence of water-carbon-phosphorous biology on Earth.

10 hours ago, kerbiloid said:

4 bar means pressure x 4 which means either temperature x 4, or air density x 4, or their intermediate combination.
Even if temperature is 1.3 greater than now (i.e. 100°C), the answer is obvious.
So, 4 bar means density x 4.

Earth atmosphere 80% consists of nitrogen released from protogenic ammonia.
It's released almost totally, so 4 bar means (400% - 80%)/(20%) = 16 times more oxygen in atmosphere.
Oxygen is made of volcanic CO2. This means 16 times more volcanic CO2 would be released.
Volcanic gases consist of H2O and CO2. H2O condensate we call "an ocean".

So, 4 bars mean 16 times more intensive vulcanic activity, 16 times greater greenhouse effect, irreversible heating and a nice second Venus instead of the Earth.

Well, you need more heating for that likely, meaning perhaps a larger moon closer to Earth (possibly spiraling in due to a super-syncronous orbit and a larger earth 1.5x Earth size?

Either way, Earth would only be habitable if it was farther out in this case. The heat would likely be too much.

7 hours ago, kerbiloid said:

 

According to the book I've read about the Earth pre-history

( Say, original version of this book:

https://books.google.ru/books?id=QHbeAq8YeXoC&lpg=PA568&ots=72H1SoPUw9&dq=sorokhtin%20ushakov%20earth&hl=ru&pg=PA449#v=onepage&q=pressure&f=false

- sorry, the original is not in English),

the Earth atmospheric pressure change was much less dramatical than that site tells.

 

As you can see here, 5-6 bar were here only once and not for a long time, right after great vulcanic activity had stopped.
Also, this CO2 has been quickly absorbed into carbonates and so on.
While a billion years later (when presumably the FeO in the Earth core will decay under the pressure into Fe and O, oxygen concentration will catastrophically increase and kill all life on the Earth).

Btw, many of the species living 60 mln years ago are still alive and feel good: mammals, birds, reptiles, so that site's data looks absolutely fantastic.
None of the mammals can live in 1 bar today and 5 bars earlier.

But I have consulted right now with this book - and you're right that 5-6 bar of O is not enough to greenhouse the Earth.
The book tells, that greenhouse would be "if the pressure would be several dozens bars".

Won't matter, the Sun will burn off all complex life on Earth by that time. The extra oxygen will only fuel Earth's Venus-like atmosphere.

[K^2]

26 minutes ago, fredinno said:

We only have evidence of water-carbon-phosphorous biology on Earth.

I'd like to hope that shortage of acetylene in Titan's oceans is due to metabolism rather than geological process. So fingers crossed for us changing that statement in the next few of decades, and adding methane-carbon-??? to this list. But for now, this is definitely true. Hence the liquid water being pretty much the definition for habitable zone.

The reason that I'm suggesting that Earth would be frozen on the surface on the outer rim of habitable zone is because we allow for a bit of an overrun to allow for something with a very dense atmosphere and very strong greenhouse effect to maintain water just above freezing, when it would have been an icicle otherwise. Which means Earth would actually have 100% ice coverage on the very edge of habitable zone.

[fredinno]

54 minutes ago, K^2 said:

I'd like to hope that shortage of acetylene in Titan's oceans is due to metabolism rather than geological process. So fingers crossed for us changing that statement in the next few of decades, and adding methane-carbon-??? to this list. But for now, this is definitely true. Hence the liquid water being pretty much the definition for habitable zone.

The reason that I'm suggesting that Earth would be frozen on the surface on the outer rim of habitable zone is because we allow for a bit of an overrun to allow for something with a very dense atmosphere and very strong greenhouse effect to maintain water just above freezing, when it would have been an icicle otherwise. Which means Earth would actually have 100% ice coverage on the very edge of habitable zone.

Actually, that area is called the "extended habitable zone". Desert planets with (almost) no water, or Super-Earths with a lot of atmosphere are habitable on the far side of that zone (which extends to Ceres) and the inner edge of the extended habitable zone is habitable by sub-earths with less atmosphere.

But yeah, Earth would likely be covered mostly by ice at the edge of the conservative habitable zone.