Abstract
1 The Melas Chasma landing site was considered a high-priority site
for the Mars Exploration Rover ( MER) mission because of the opportunity
to land on and study potential layered sedimentary deposits. Though
no longer considered a candidate site because of safety concerns,
the site remains a scientifically interesting area that provides
insight into the geologic history of Valles Marineris. Within the
landing ellipse are dunes, landslide material, and unusual blocky
deposits. The blocky deposits are composed of rounded blocks, some
of which have meter-scale layering, and they show evidence of ductile
deformation, including bending and distortion of coherent blocks
around each other. The morphologic characteristics of the blocks
are unique, and they appear to have no terrestrial analogue. However,
the gross morphology of these blocky deposits and their superposition
on adjacent wallrock is consistent with the blocks having been transported
downslope. Given the existence of other large mass failures in the
area, we propose the blocky deposits may also have originated from
mass movement events. The size of the blocks coupled with the distances
they traveled indicates high mobility. The distances the blocks were
transported and their rounded, irregular shapes suggest either water
in the source material or deposition in a subaqueous environment.
The source for the main blocky deposit inside the landing ellipse
is considered to be the wallrock to the south, while the other two
blocky deposits have source regions along the northern canyon walls.
The southern wallrock of Melas Chasma contains numerous valleys not
seen elsewhere in Valles Marineris. The identification of valley
networks along the southern wallrock suggests that a source of water
existed below the surface of the plateau and produced the valleys
after intersecting the edge of the exposed canyon walls.
Users
Please
log in to take part in the discussion (add own reviews or comments).