Earth’s Magnetic Field

At http://tallbloke.wordpress.com/2012/05/14/solar-wind-stripping-atmospher… there is a post on a chance alignment of planets during a passing gust of the solar wind that has allowed scientists to compare the protective effects of Earth's magnetic field with that of Mars, which as a negligible atmosphere. It was found that pressure from the solar wind led to loss of oxygen on Mars at a rate ten times higher than on Earth – which explains why the atmosphgere of Mars is depleted (as a result of continous bombardments from the solar wind),