Temperature and Area Constraints of the South Volund Volcano on Io from 
the NIMS and SSI Instruments during the Galileo G1 Orbit.

A.G.Davies, A.S.McEwen, R.Lopes-Gautier, L.Keszthelyi, R.W.Carlson and
W.D.Smythe.


Analysis of data from darkside and eclipse observations of Io by
the NIMS and SSI instruments show that the South Volund hot spot is
probably a silicate lava flow, a series of smaller fissure-fed flows,
or a lava lake.  The multispectral color temperatures from NIMS are 
compared with the brightness temperatures from the SSI instrument, 
and show excellent agreement for the hotter of the two modelled 
components.  The temperatures and areas of these components are 
consistant with silicate volcanic activity when modelled with a two 
temperature fit.  The two components might correspond to a cooled
crust which has formed on the surface of an active flow or lava lake,
at a temperature of approximately 450 K, and covering an area of about
50 km2, and a hotter and much smaller component, at a temperature of
approximately 1100 K and an area of less than 0.1 km2.  The hot 
component corresponds to either cracks in the surface crust through 
which the hot interior radiates, a hot vent area, or breakouts of 
lava forming new lobes.