The Earth's magnetosphere protects the planet from solar winds and high-energy particles by redirecting this energy around the planet. When charged particles approach the Earth, the magnetosphere affects them due to their magnetic properties. Particles blown by the solar wind simply sweep around the Earth, while slower radioactive particles may become part of the Earth's radiation belts, held safely above the surface by the magnetosphere.
In 2012 the European Space Agency was able to demonstrate the protective effect of Earth's magnetosphere. When a wave of solar wind struck both Earth and Mars, the agency measured the effects of the impact on both planets. In both cases, the solar wind depleted the planets' atmospheres of oxygen, but the effect on Mars was approximately 10 times as severe. This may explain why the planet Mars has such a thin atmosphere, as over time the solar wind would deprive it of many of its heavier molecules. Study of the planet Mercury has shown its atmosphere is constantly being blown from its surface by the intense solar winds at the heart of the solar system.
While the term "magnetosphere" implies a circular structure, in reality the Earth's magnetosphere resembles a comet's tail. The side nearest the sun is compressed by the solar wind, while on the night side, the magnetic field draws out in a tail that may be 1,000 times as long as the diameter of the planet.