IO SODIUM JET. Astronomers have previously known of a sodium cloud which precedes the moon Io in its orbit around Jupiter. The cloud is believed to arise from slow escape of sodium from Io. Now the Galileo spacecraft is providing details of another sodium feature at Io, more of a fast-escaping spray or jet, thought to come about when Io plows through Jupiter's potent magnetic field, a process which induces mega-amp currents through Io's atmosphere (see schematic at www.aip.org/png). New pictures, reported by scientists at the University of Colorado (Matthew Burger, burger@ganesh.colorado.edu, 303-492-3395, and Nicholas Schneider) and Boston University (Jody Wilson), localize the source of the sodium to a region smaller than Io's diameter, suggesting that Io's atmosphere might not be global; that is, the atmosphere might be patchy and not extend all the way to the poles. (Geophysical Research Letters, 15 November.)