Large amounts of interplanetary dust particles floating freely in space. Also called cosmic dust, the particles are created by collisions among asteroids or released by comets as they pass by the sun. Large dust clouds can act as a shield to block out solar radiation from reaching the earth, effectively cooling the planet and helping to combat global warming.

Instead of having a dust cloud floating by itself in space, scientists have conceived the idea of using a large asteroid placed at the L1 point in space, a site where the gravitational pull of the sun and the earth cancel out, to gravitationally anchor a dust cloud in space to block sunlight and cool the earth. In this scenario, a mass driver consisting of electromagnets is used to hurl asteroid-derived matter away from the giant asteroid. The mass driver can also serve as a rocket to push the asteroid to the L1 point and then as an engine to spew out sun-shielding dust.