HR: 15:10h
AN: P53C-07 INVITED [Abstracts]
TI: New Horizons at Jupiter: Observations of Io
AU: * Spencer, J R
EM: spencer@boulder.swri.edu
AF: Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, United
States
AU: Science Team, N
EM: spencer@boulder.swri.edu
AB:
Jupiter's volcanic moon Io was a prime target for the New Horizons
spacecraft during its early 2007 Jupiter flyby. 190 grayscale images,
17 color images, and 7 near-infrared image cubes, and numerous
ultraviolet spectra were taken during the flyby in order to map
changes in surface appearance, volcanic plumes, and hot spots since
the last close-up observations, by Galileo in late 2001. Best imaging
resolution was about 12 km/pixel. The result was the most
comprehensive global snapshot of Io volcanism yet obtained. Numerous
small surface changes were seen along with several large changes,
including new pyroclastic deposits associated with two major new lava
flows in the southern hemisphere. Several new volcanic plumes were
seen, but several plumes first seen by the Voyager spacecraft in 1979
continue to be active. Most dramatic was a 330 km high plume from the
Tvashtar volcano, which provided the most detailed view yet of a large
Pele-class Io plume. The plume maintained similar size and appearance
for eight days, displaying a bright top and little evidence for a
column of upgoing particles, suggesting that most visible particles
condense out of the plume gases during flight rather than being
ejected directly from the vent. Intricate filamentary structure
in the plume allows direct tracking of plume motions,
revealing projected speeds up to 0.7 km s-1.
Images of Io in Jupiter eclipse show visible-wavelength auroral glows
from all plumes and also very localized emission from most surface
volcanic features near the sub-Jupiter and anti-Jupiter hemispheres, a
phenomenon seen previously by Galileo. The glows do not correlate
with infrared thermal emission, suggesting that a non-thermal process
is illuminating gas tens of kilometers above volcanos in these locations.
DE: 5405 Atmospheres (0343, 1060)
DE: 5408 Aurorae and airglow
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6219 Io
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting