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J.K. Wilson, M. Mendillo (Boston U.), J. Spencer (Lowell Obs.), J. Stansberry (U. of Arizona)
Io's volcanoes are the ultimate source of Io's atmosphere, its extended neutral clouds, and the heavy ions of sulfur and oxygen in Jupiter's magnetosphere. Groundbased and spacebased infrared observations have shown that the level of volcanic activity on Io is highly variable. Images of the sodium “nebula” around Jupiter have shown that the escape of neutrals from Io’s atmosphere is also variable, both in the rate of escape and the means of escape. We have now merged a large infrared data set with a decade of nebula observations, and we find that the escape of material from Io's atmosphere varies systematically with volcanic activity. Our results indicate that a molecular form of sodium, probably NaCl (1), is more abundant in Io's atmosphere during volcanically active periods than during volcanically quiet periods. It is likely that the abundances of the more dominant species (SO2, S, O, etc.) are also controlled by volcanoes. Since the neutral clouds are indirectly indicative of mass input into the plasma torus, it follows that Io's dynamic volcanism may be a primary cause of long-term variability in Jupiter's plasma torus and overall magnetosphere.
At B.U., this work was supported in part by grants from the Magnetospheric Physics Program at NASA, and by seed research funds provided to the Center for Space Physics. Work at Lowell is supported by grants NAG5-9004 and NAG5-10497 from the NASA Planetary Astronomy and Planetary Geology and Geophysics programs.
(1) Lellouch, E., G. Paubert, J. I. Moses, N. M. Schneider, D. F. Strobel, Volcanically emitted sodium chloride as a source for Io’s neutral clouds and plasma torus, Nature, 421, 45-47, 2003.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.