View Full Version : Earth with a 0.5 bar atmosphere

2012-Oct-02, 04:33 PM
What would the climate be like?
How would things be different for life?
Lets say we have the same composition of elements in the atmosphere but its just 0.5 bar.

2012-Oct-02, 04:48 PM
The pressure on top of Mt Everest is about 0.33 bar, and there is some life there, and acclimatized humans can survive there briefly.

2012-Oct-02, 04:53 PM
Like what would be different with the climate like the water cycle?
How would it affect society in general and the things we use?
How would life be affected and how would it adapt?

2012-Oct-02, 05:00 PM
Do you mean if there were a sudden change and life forms we're familiar with had to adapt, or if it had always been this way and life evolved in that environment?

2012-Oct-02, 05:10 PM
No i mean if it was always like this and life evolved in this environment.

2012-Oct-02, 06:06 PM
Since we don't know exactly how life started and how it evolved, it's kind of hard to say how it would be different. My first thought is that the development of flight would have been delayed (or absent). Also, with the low pressure, there might be less liquid water, so if life evolved from water, this would certainly change things. Under these circumstances, life might evolve slower because less liquid water means less opportunity for life to form. On the other hand, it might evolve quicker because with less atmospheric pressure, viable life could form without having to evolve as strong a cellular structure. These are just random thoughts because I really don't know, but it is interesting to ponder.

2012-Oct-02, 06:14 PM
The atmospheric pressure of Earth's atmosphere has almost certainly changed over the history of Earth (the composition has obviously changed too).

Though it is not exactly know what the historic pressure was, this article from the American Chemical Society (http://pubs.acs.org/subscribe/archive/ci/30/i12/html/12learn.html) gives a lot of information about it.

What was the air pressure for the 97% of Earth’s life before the age of dinosaurs? We have three possible alternatives, as shown in Figure 1.

The pressure could have been at 1 bar throughout Earth’s earlier life, risen to 4–5 bar ~100 Mya (just at the time when the giant fliers needed it), and then returned to 1 bar (curve A).
The pressure could have been ~4–5 bar from Earth’s beginning, 4600 Mya; and ~65 Mya, it could have begun to come down to today’s 1 bar (curve B).
The atmosphere could have started at higher pressure and then decreased continuously through Earth’s life to ~4–5 bar ~100 Mya and down to 1 bar today (curve C).

2012-Oct-02, 10:37 PM
How would humans and other creatures adapt if exposed to this?
How would the climate change and what would be the differences?

2012-Oct-03, 02:14 AM
In regards to the climate i would say even with a 70 mph gust of wind, the effects would be less pronounced. With less air there would be less damage from storm winds. I would also say that there would be less thunderstorms and more rain showers because there would be less air for the storm to rise in, overall storms might be less severe. Would that be right? Also when it comes to humans we would need larger lungs to take in more oxygen so maybe we would be smaller also. I know there are some people who live in high elevations on the Andes mountains and the Himalayas.