magnitude of −4.7, similar to that of Venus from Earth. At only 8 arcminutes across, its disc would be barely discernible. Amalthea's orbital period is only slightly longer than its parent planet's day (about 20% in this case), which means it would cross Jupiter's sky very slowly. The time between moonrise and moonset would be over 29 hours. Science journalist Willy Ley suggested Amalthea as a base for observing Jupiter, because of its nearness to the planet, almost synchronous orbit, and small size making a landing easy. From the surface of Amalthea, Jupiter would look enormous: at 46 degrees across, it would appear roughly 85 times wider than the full moon from Earth. Because Amalthea is in synchronous rotation, Jupiter would not appear to move, and would not be visible from one side of Amalthea. The Sun would disappear behind Jupiter's bulk for an hour and a half each revolution, and Amalthea's short rotation period gives it just under six hours of daylight. Though Jupiter would appear 900 times brighter than the full moon, its light would be spread over an area some 8,500 times greater and it would not look as bright per surface unit. Exploration During 1979, the unmanned Voyager 1 and Voyager 2 space probes obtained the first images of Amalthea to resolve its surface features. They also measured the visible and infrared spectra and surface temperature. Later, the Galileo orbiter completed the imaging of Amalthea's surface. Galileo made its final satellite fly-by at a distance of approximately from Amalthea's center (at a height of about 160–170 km) on 5 November 2002, permitting the moon's mass to be accurately determined, while changing Galileo's trajectory so that it would plunge into Jupiter in September 2003 at the end of its mission. In 2006, Amalthea's orbit was refined with measurements from New Horizons. In fiction Amalthea is the setting of several works of science fiction, including stories by Arthur C. Clarke, James Blish and Arkady and Boris Strugatsky. See also Galilean moons (the four biggest moons of Jupiter) Notes References Cited sources External links Amalthea Profile by NASA's Solar System Exploration Amalthea nomenclature from the USGS planetary nomenclature page Jupiter's Amalthea Surprisingly Jumbled – JPL press release (2002-12-09) Jupiter From Amalthea, a painting by Frank Hettick, 2002. Animated 3D shape model of Amalthea Moons of Jupiter Discoveries by Edward Emerson Barnard 18920909 Moons with a prograde orbit