2006-12-04 20:46:19 · 5 answers · asked by Kelvin K 2 in Science & Mathematics ➔ Physics
All planets (and most moons) will have created their own atmosphere at some stage during their geological creation. All atmosphere is..........is gas. Commonly the gas that makes up an atmosphere will first be created by releases from volcanic activity. This will then be modified by other factors (in Earth's instance from the presence of plant life removing carbon dioxide and adding oxygen).
Whether the planet (or moon) keeps its atmosphere is entirely dependent on the mass (size) of the planet and therefore whether it produces enough gravity to hang on to the atmosphere.
Happily the Earth is just at the right size to keep a thick enough atmosphere to support life. Any smaller and the atmosphere would be lost, or extremely thin as it is on Mars.
2006-12-04 20:53:49 · answer #1 · answered by the_lipsiot 7 · 1⤊ 0⤋
Earth has a breathable atmosphere. Oxygen is the gas that is required for the life of most creatures. This is present in Earth's atmosphere, along with nitrogen, and in water, along with hydrogen. Oxygen is constantly put into the atmosphere by plants and trees. Fortunately, Earth's atmosphere does not contain much carbon dioxide, a poisonous gas which makes up most of the atmosphere of planets like Venus and Mars. In densely-populated areas, carbon dioxide is more present. This is because cars and factories produce it. This causes the air to be polluted. The Earth's atmosphere is kept on the planet by its pull of gravity. Mars and Mercury are too small to keep atmosphere. As a result, Mercury has no atmosphere, and Mars' atmosphere is very thin, containing gases which have not managed to escape into space yet. Earth's atmosphere is thick enough to prevent poisonous rays of radiation from getting through it (this is what has happened on Mars).
2006-12-05 04:47:47 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The quick answer is "gravity".
There was a time when the earth was a ball of hot molten rock. Over time as it cooled it gave off gasses and vapours which stayed close to the surface due to the attractive force of gravity. It is for this reason too that the atmosphere is most dense at sea level and progressivley thinner the higher you go. At elevations such as the top of Mount Everest you can barely get enough oxygen to survive.
The current composition of the atmosphere is a little more complicated to explain but much of it has to do with many millions of years of plants, especially very small aquatic plants, that have provided us with oxygen and removed carbon-dioxide and "fixed" (or removed) other substances like nitrogen and sulphur.
2006-12-05 04:59:59 · answer #3 · answered by Anonymous · 1⤊ 0⤋
cos its one of those things that just is
2006-12-05 04:47:44 · answer #4 · answered by king of spain 3 · 0⤊ 3⤋
Because God gave it to us. :-) Thankfully!
2006-12-05 04:53:47 · answer #5 · answered by Katie 3 · 1⤊ 2⤋