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Landform degradation and slope processes on Io: The Galileo view
Journal of Geophysical Research-Planets, 106 (E12): 33223--33240 (2001)
Аннотация
The Galileo mission has revealed remarkable evidence of mass movement
and landform degradation on Io. We recognize four major slope types
observed on a number of intermediate resolution (similar to250 m
pixel(-1)) images and several additional textures on very high resolution
(similar to10 m pixel(-1)) images. Slopes and scarps on Io often
show evidence of erosion, seen in the simplest form as alcove-carving
slumps and slides at all scales. Many of the mass movement deposits
on Io are probably mostly the consequence of block release and brittle
slope failure. Sputtering plays no significant role. Sapping as envisioned
by McCauley et al. 1979 remains viable. We speculate that alcove-lined
canyons seen in one observation and lobed deposits seen along the
bases of scarps in several locations may reflect the plastic deformation
and "glacial" flow of interstitial volatiles (e.g., SO2) heated by
locally high geothermal energy to mobilize the volatile. The appearance
of some slopes and near-slope surface textures seen in very high
resolution images is consistent with erosion from sublimation-degradation.
However, a suitable volatile (e.g., H2S) that can sublimate fast
enough to alter Io's youthful surface has not been identified. Disaggregation
from chemical decomposition of solid S2O and other polysulfur oxides
may conceivably operate on Io. This mechanism could degrade landforms
in a manner that resembles degradation from sublimation, and at a
rate that can compete with resurfacing.
