Chapter 43 - Volcanism on Io

differentiation The process by which planets and satellites develop layers or zones of different chemical and mineralogical composition. flyby Term used to describe the close approach of a spacecraft to a body, without the spacecraft going into orbit around that body. Galilean satellites The four largest satellites of Jupiter (Io, Europa, Ganymede, Callisto), named after their discoverer Galileo Galilei. heat flow Heat that comes out of a body from its interior and is ultimately radiated to space. hot spots Regions of enhanced thermal emission on Io, a sign of volcanic activity. The term does not imply a particular eruption mechanism, and does not have the same meaning as hot spots on Earth. IRIS Acronym for Infrared Interferometer Spectrometer, an instrument aboard Voyager. NIMS Acronym for Near-Infrared Mapping Spectrometer, an instrument aboard Galileo that obtained spectra in the wavelength range 0.7e5.2 mm. The spectra are used to analyze the composition of Io’s surface and to measure the temperatures of its volcanic regions. Patera A collective term for a variety of saucer-shaped, shallow volcanic constructs that often have a central caldera-like depression. pyroclastic materials Fragmented materials ejected during a volcanic eruption, including ash, pumice, and rock fragments. SSI Acronym for solid state imaging system, the CCD camera aboard the Galileo spacecraft. sulfur allotropes Sulfur cooled rapidly from different temperatures, resulting in different colors. thermal emission Electromagnetic radiation produced by a body due to its temperature. volatiles Chemical compounds or elements contained in magmas that are generally released as gases to the atmosphere during a volcanic eruption.