JUPITER'S MOON IO BEARS WATCHING. The most volcanically active object in the solar system, Io has recently been visited again (in Feb /pnu/2000/) by the Galileo spacecraft, and the surface shows noticeable changes from a flyby made in Oct 1999. Results reported at last week's American Geophysical Union meeting in Washington, DC include the following: John Spencer of the Lowell Observatory summarized infrared observations of Loki, Io's (and the solar system's) greatest volcano, whose immense lava flow, the size of Connecticut, is unequaled on Earth in historic times. In the past few months the flow has warmed by 40 K and greatly grown.

Rosaly Lopes-Gautier of JPL showed several new hot spots (potential volcanos) discovered with a high-resolution infrared spectrometer. One might extrapolate from the density of sources, she said, that Io might have more than 300 volcanos, representing a colossal energy loss.

Meanwhile, Alfred McEwen of the University of Arizona described the Chaac canyon which, with a depth of 2.8 km and an average steepness of 70 degrees, is much more dramatic than the Grand Canyon in Arizona (1.5 km deep and 30 degrees in steepness). See also Science, 19 May /pnu/2000/.