One of the most enticing ideas came this morning from Jim Green, NASA’s Planetary Science Division Director. In a talk titled, “A Future Mars Environment for Science and Exploration,” Green discussed launching a “magnetic shield” to a stable orbit between Mars and the sun, called Mars L1, to shield the planet from high-energy solar particles. The shield structure would consist of a large dipole—a closed electric circuit powerful enough to generate an artificial magnetic field.

Such a shield could leave Mars in the relatively protected magnetotail of the magnetic field created by the object, allowing the Red Planet to slowly restore its atmosphere. About 90 percent of Mars’s atmosphere was stripped away by solar particles in the lifetime of the planet, which was likely temperate and had surface water about 3.5 billion years ago.