On the Moon, water molecules and other volatiles are thought to migrate along ballistic trajectories. Here, this migration process is described in terms of a two-dimensional partial differential equation for the surface concentration, based on the probability distribution of thermal ballistic hops. A ...
Solar Dynamics Observatory (SDO), U.S. satellite designed to study the Sun. It was launched on February 11, 2010. SDO is the first satellite in NASA’s Living with a Star program, which studies space weather—that is, the effects of solar activity on Ear