Dec 16 2000
From The Space Library
Ganymede, the largest moon in Jupiter's solar system, joined the planet Mars and Jovian moons Europa and Callisto as the only known bodies showing strong evidence of the presence of liquid water beneath their surfaces. During the annual meeting of the American Geophysical Union, Margaret G. Kivelson, a planetary scientist at the University of California at Los Angeles, announced that NASA's Galileo spacecraft had found evidence of a vast sea of liquid beneath the surface of Jupiter's moon Ganymede. Using data collected from Galileo's magnetometer during May 2000 and earlier, Kivelson's team had measured the moon's magnetic field. The magnetometer had registered readings "best explained by a thick layer of water-about as salty as Earth's oceans-hidden about 120 miles [190 kilometers] beneath" the moon's surface. Thomas B. McCord, a geophysicist at the University of Hawaii who also presented research at the conference, had used Galileo's Near Infrared Mapping Spectrometer to discover that portions of Ganymede appeared "to have types of salt minerals that would have been left behind by exposure of salty water near or onto the surface." Gene D. McDonald, an astrobiologist at JPL, which manages the Galileo Mission, remarked that Ganymede might be a more promising destination than Europa for robotic spacecraft searching for life. Ganymede, farther from Jupiter than Europa, has better protection than Europa from Jupiter's intense and deadly radiation. Therefore, biomarker compounds emerging on the surface of Ganymede would survive longer there than on the other Jovian moons, as would any spacecraft orbiting or landing on Ganymede.
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