Abstract
Sets of ridges of uncertain origin are seen in twenty-nine high-resolution
Galileo images, which sample seven locales on Io. These ridges are
on the order of a few kilometers in length with a spacing of about
a kilometer. Within each locale, the ridges have a consistent orientation,
but the orientations vary from place to place. We investigate whether
these ridges could be a result of tidal flexing of Io by comparing
their orientations with the peak tidal stress orientations at the
same locations. We find that ridges grouped near the equator are
aligned either north-south or east-west, as are the predicted principal
stress orientations there. It is not clear why particular groups
run north-south and others east-west. The one set of ridges observed
far from the equator (52degrees S) has an oblique azimuth, as do
the tidal stresses at those latitudes. Therefore, all observed ridges
have similar orientations to the tidal stress in their region. This
correlation is consistent with the hypothesis that tidal flexing
of Io plays an important role in ridge formation. (C) 2004 Elsevier
Inc. All rights reserved.
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