The repair mission for the Hubble space telescope, as astronauts try to fix crucial equipment that was not designed to be repaired in orbit; studies on the brain of an epileptic to try to understand more about the link between brain structure and memory; using new data from cave stalagmites and the Mississippi riverbed to understand how and why earthquakes strike in the heartland; and a profile of neurosurgeon Alfredo Quinones-Hinojosa.