Oct 22 1998
From The Space Library
Scientists studying Galileo data published findings in the journal Nature describing the likely presence of a subsurface, liquid, salty ocean on Callisto, Jupiter's second largest moon. Margaret G. Kivelson, space physics professor at the University of California at Los Angeles and NASA's Principal Investigator for Galileo's magnetometer instrument, explained that data showed variability in Callisto's magnetic field similar to that of another Jupiter moon, Europa. However, neither Callisto's atmosphere, which lacks charged particles, nor Callisto's icy crust, is a good conductor for generating a magnetic field. Kivelson explained that a layer of salty melted ice could carry "sufficient electrical currents to produce the magnetic field." In addition, she noted that Galileo data indicated electrical currents flowing in opposite directions at different times, a "key signature consistent with the idea of a salty ocean." However, scientists had concluded that, unlike Europa, Callisto was unlikely ever to support life, even if it had an ocean, because of its insufficient energy sources. Callisto's only apparent source of heat is radioactive elements, whereas Europa's closer position to Jupiter means it possesses tidal energy.
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