Scientists half-jokingly call it the "ignorosphere" -- a region about 50-100 kilometers above the Earth that's too high for airplanes, but too low for satellites. "It earned its name because even though the area is valuable to researchers, there has been no easy way to get to it," said Alan Stern, planetary scientist at the Southwest Research Institute. But, Stern says, suborbital flights, like those made by Virgin Galactic's SpaceShipTwo, go right to the heart of this region, which includes the layer of the Earth's atmosphere that lies above the stratosphere and below the thermosphere.