astroengine writes "At one time, Mars had a thick, protective atmosphere — possibly even cushier than Earth's — but the bubble of gases mostly dissipated about 4 billion years ago and has never been replenished, new research shows. The findings come from NASA's Mars rover Curiosity, which has been moonlighting as an atmospheric probe as it scours planet's surface for habitats that could have supported ancient microbial life. 'On Earth, our magnetic field protects us, it shields us from the solar wind particles. Without Earth's magnetic field, we would have no atmosphere and there would be no life on this planet. Everything would be wiped out — especially when you go back 4 billion years. The solar wind was at least 100 times stronger then than it is today. It was a young sun with a very intense radiation,' Chris Webster, manager of the Planetary Sciences Instruments Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News. Unfortunately for Mars, the last 4 billion years have not been kind."