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Say if a planet had either no greenhouse gases or a small percentage of a certain greenhouse gas (roughly 5% or less) in its atmosphere, but all other elements in the atmosphere could support life. What would be the effects of this certain type of atmosphere on the planet and biota (if organisms could evolve on the world)?
Twig
Posted 2016-08-16T22:37:51.500
Reputation: 311
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If there is CO2 in the soil then I think purple bacteria could be supported.
Without greenhouse gases present in the atmosphere of such a planet, there is no weather. As for the development of life, I'm unsure.
"...greenhouse effect, which acts to warm the lower atmosphere and cool the upper atmosphere, and atmospheric convection (thermals, clouds, precipitation) ... cools the lower atmosphere and warms the upper atmosphere.
There would probably still be some horizontal wind flows associated with the fact that the poles would still be cooler than the tropics..." (Spencer, 2009.)
Source:
David your friend
Posted 2016-08-16T22:37:51.500
Reputation: 121
2Seems a bit silly and overstated. Uneven heating of the Earth cause weather (weather being the redistribution of this energy). Yes the greenhouse gasses play their part, but stating without them there would be no weather is extreme and a bit silly. – Twelfth – 2016-08-17T19:40:11.767
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The Earth has an average temperature of about 15 degrees. Without the greenhouse effect, the average temperature would be sub-zero, and so the Earth would be ice covered.
If the planet were closer to the sun though it could compensate and leave the planet at the same temperature.
Carbon dioxide is an effective greenhouse gas. Without CO2 plants couldn't grow. If a planet has no CO2 it would be worth asking where all the carbon is. If a planet has no carbon, then life is hard to make work (carbon forms most of the interesting chemicals of life.) And if there is life that is respiring, it would be making CO2. Water vapour is also a greenhouse gas. It is hard to imagine life without carbon, harder still to imagine it without water, and most of the alternatives: ammonia, methane... they are also greenhouse gasses.
So planets with life probably do have a greenhouse effect.
James K
Posted 2016-08-16T22:37:51.500
Reputation: 9 236
What if C02 was in the planet's crust and/or soil and could be recycled through biological processes somewhat like the nitrogen cycle. Could life as we know it exist? – Twig – 2016-08-17T00:05:05.873
@Twig CO2 is already cycled like this here on Earth. Plus there's a lot of it locked in the Earth's crust. A low CO2 atmosphere planet would be very cold, presumably life could exist there. Just like here. – a4android – 2016-08-17T05:24:37.517
Don;t forget that CO2 levels have been falling for geological ages. Current CO2 concentrations in the atmosphere are getting close to "starvation level" for plants, supplementary concentration of CO2 in greenhouses provides the maximum output at something like 1500 -2000 ppm, well above the current 400ppm level observed today. In 500 million years, it is thought the CO2 levels will have dropped to the point plant life may become extinct (but since the Sun will be much more luminous, the greenhouse effect will not be that much of a factor then). – Thucydides – 2016-08-17T19:40:52.987
@Thucydides what do you mean "that much of a factor then"? – Twig – 2016-08-17T20:18:18.633
The increased luminosity of the sun will make the Earth progressively hotter, even without any atmosphere at all. – Thucydides – 2016-08-17T21:08:45.653
2Define greenhouse gas....remember water vapor is one of the strongest. Water, Methane, co2, ozone, nitrous oxide, and a couple others are the usual ones we consider. – Twelfth – 2016-08-16T23:44:55.067
1@Twelfth the greenhouse gas I was considering was just water vapor, but only a small percentage of it. – Twig – 2016-08-16T23:49:39.450
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Low water vapour suggests a very dry planet and possibly a very cold one too. This could be a Snowball Earth. Snow and ice lower water vapour in the air. https://en.wikipedia.org/wiki/Snowball_Earth Life could still evolve around hydrothermal vents and go on to colonise the rest of the planet. Quite plausible.
– a4android – 2016-08-17T05:29:34.4533All greenhouse gases on earth do total <5% by volume; about 97% is nitrogen and oxygen – nzaman – 2016-08-17T09:12:08.173
So only three percent or lower could create a habitable planet? – Twig – 2016-08-17T19:48:24.857
@Twig- more like point three percent or lower. Here's a link that should help: http://climate.ncsu.edu/edu/k12/.AtmComposition
– cobaltduck – 2016-08-17T20:20:27.973