@Setanta,
Setanta wrote:
You shouldn't shoot your mouth off when you don't know what you're talking about. Gravity is not some big magnet. It is an expression (and an imprecise term, too) of the attractive nature of mass. It doesn't take that much mass to pin an atmosphere to a planet--or a moon such as Saturn's moon Titan, from which I have suggested we could get nitrogen.
Gases expand as they warm, and so cold planets can have denser atmospheres than warmer ones.
If you started trying to pressurize Mars' atmosphere by adding gas, the gas would begin piling up as long as it was cold, but the moment the greenhouse effect caused it to warm up, it would expand very quickly and get blown away by solar wind.
Even Earth would lose its atmosphere to solar wind if it weren't for the magnetic field caused by our molten core. As the upper atmosphere would be shaved away, the lower atmosphere would rise higher and thus decompress, lowering the boiling point of water, which would cause liquid water to vaporize, and the greenhouse effect from the vapor would result in a vicious cycle of vaporization and atmosphere loss until we were left with a relatively thin, cold atmosphere.
Earth's atmosphere in the absence of its magnetic field (molten core) would probably not be as thin as Mars' due to Mars having 1/3 Earth's gravity, but the magnetic field supposedly prevents atmosphere loss that would otherwise occur due to direct bombardment by solar wind.
Quote:This is from
NASA's Solar System Exploration page about Titan:
As exotic as Titan might sound, in some ways it’s one of the most hospitable worlds in the solar system. Titan’s nitrogen atmosphere is so dense that a human wouldn’t need a pressure suit to walk around on the surface. He or she would, however, need an oxygen mask and protection against the cold—temperatures at Titan’s surface are around minus 290 degrees Fahrenheit (minus 179 Celsius).
At cold temperatures, denser atmosphere means faster heat-loss. Denser and more humid air feel colder because they don't insulate as well as dry air that is less dense. Vacuum is ultimately the best insulator, which is why vacuum thermoses are so efficient.
Quote:Titan’s dense atmosphere, as well as gravity roughly equivalent to Earth’s Moon, mean that a raindrop falling through Titan’s sky would fall more slowly than on Earth.
And that it would be frozen solid, not that water is ever likely to evaporate at -180C.
Quote:While Earth rain falls at about 20 miles per hour (9.2 meters per second), scientists have calculated that rain on Titan falls at about 3.5 miles per hour (1.6 meters per second), or about six times more slowly than Earth’s rain. Titan’s raindrops can also be pretty large. The maximum diameter of Earth raindrops is about 0.25 inches (6.5 millimeters) while raindrops on Titan can reach diameters of 0.37 inches (9.5 millimeters), or about 50 percent larger than an Earth raindrop.
The rain is methane, not water.
Quote:Titan has 0.0225 the mass of the Earth. Mars, by contrast, has about 11% the mass of Earth. Using the atmospheric pressure of Earth at mean sea level as a base line, that means that the atmospheric pressure on mean surface level on Titan is 1.45 atmospheres--much denser and heavier than our atmosphere.
You should take to heart the dictum that it is better to remain silent and be thought a fool than to open your mouth and remove all doubt.
Not at all. If you don't post something for discussion, there's nothing to discuss. Better to post a wrong answer in order to stimulate discussion of why it's wrong and what the right answer is and why, then to keep silent and allow lots of people with similar gaps in their knowledge/reasoning to go on assuming things that are obstructing their progress toward truer perspective.
