... To help better understand the Earth's surface, slight distance changes between a pair of identically orbiting satellites named GRACE have been used to create the best ever map of Earth's gravitational field. ... Large storms on Earth can spawn unusual, small, violent clouds known as tornadoes. ... Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars. An Ion Drive for Deep Space 1 . ... Mars Simulated View . ...