NASA’s Galileo spacecraft continues to deliver surprises with the discovery that Jupiter’s potato-shaped inner moon, named Amalthea, appears to have a very low density, indicating it is full of holes. “The density is unexpectedly low,” said Dr. John D. Anderson, an astronomer at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Amalthea is apparently a loosely packed pile of rubble.” The empty gaps between solid chunks likely take up more of the moon’s total volume than the solid pieces, and even the chunks are probably material that is not dense enough to fit some theories about the origin of Jupiter’s moons. “Amalthea now seems more likely to be mostly rock with maybe a little ice, rather than a denser mix of rock and iron,” said JPL’s Dr. Torrence Johnson, project scientist for Galileo.
Reddish spots on the icy surface of Jupiter’s moon Europa may indicate pockets of warmer ice rising from below. This upwelling could provide an elevator ride to the surface for material in an ocean beneath the ice, say scientists studying data from NASA’s Galileo spacecraft.
Before starting its 35th and final orbit around Jupiter next week, NASA’s Galileo spacecraft will visit three intriguing features of the giant planet’s neighborhood for the first time: a small moon named Amalthea, a dusty ring and the inner region of Jupiter’s high-energy magnetic environment.
With scientific instruments on NASA’s Voyagers, Galileo, Cassini and more than two dozen other spacecraft, University of Iowa physicist Dr. Don Gurnett has been recording waves that course through the thin, electrically charged gas pervading the near-vacuum of outer space. Gurnett converted the recorded plasma waves into sounds, much as a receiver turns radio waves into sound waves. “I’ve got a cardboard box full of cassette tapes of sounds that I’ve collected over nearly 40 years,” he said. Gurnett’s tapes have inspired a 10-movement musical composition called “Sun Rings.” The Grammy-nominated Kronos Quartet will premiere “Rings” this month.