Talk:Coronal Mass Ejections

Radiation shielding on Mars

The article states that "the Earth's atmosphere has the protective thickness equivalent to 32 meters of water". The Lunarpedia article referred to for the thickness of water that has a protective equivalent of Earth's atmosphere actually stated that Earth's atmosphere is equivalent to 32 feet of water. That equals about 9.75 meters. That is closer to the correct answer, but we can do better than that. According to the Wikipedia article on the pascal, the Earth's atmospheric pressure is equal to 101,325 pascal (or newtons per square meter). Divide that by 9.8 newtons per kilogram (Earth's gravity) and you get 10,340 kilograms per square meter. For water that is 10.34 cubic meters. A column of water 1 meter square and 10.34 meters high would have that volume and exert the pressure of one atmosphere on it's one square meter base on Earth. So 10.34 meters or 34 feet is the water equivalent of one atmosphere of pressure. That thickness of water also provides about the same radiation protection as Earth's atmosphere. If you divide that by the density of Mars, 3.9, you get 2.65 meters of Mars to give radiation protection like Earth's atmosphere. However the regolith at the surface is porous so we should only count on a density of 3, giving us a thickness of 3.4 meters of regolith to provide an Earth's atmosphere of radiation protection to a dwelling on Mars. --Farred 02:00, 26 October 2010 (UTC)