Last Days at Saturn

摘要

Cassini, an unmanned spacecraft the size of a small school bus, was orbiting Saturn on December 5,2010, just as it had been every day for more than six years, when one of its dozen instruments went berserk. Called RPWS, for Radio and Plasma Wave Science, the instrument monitors radio signals emanating from the giant gas planet, clues to the changing condition of its magnetic fields, as well as lightning in its turbulent atmosphere. On one pass, everything was normal. On the next pass the signals "had totally changed," recalls Andy Ingersoll, an atmospheric scientist at the California Institute of Technology in Pasadena.