MAGELLAN PROJECT OFFICE

MIT ID: GSDRP.1;2
JPL ID: P-40144
Date:   5/4/92

These images display the meter-scale  roughness  of  the  Venus  surface
(characterized  by  its  root-mean-square average slope), as observed by
the Magellan radar altimeter.  The lightest shades locate  areas  having
the steepest values of average slope, while darker shades indicate areas
that are smoother.  The upper  image  shows  that  part  of  the  planet
between  69  degrees  north  and  69  degrees south latitude in Mercator
projection; beneath it are the  two  polar  regions  covering  latitudes
above  44  degrees in stereographic projection.  Easterly longitudes run
across the Mercator map from left to right, and around the periphery  of
the  polar  stereographic projections.  Resolution of the surface varies
with spacecraft altitude, being about 10 kilometers near the equator and
degrading  to  as  much as 25 kilometers at high latitudes.  Black areas
indicate where data had not yet been  obtained  by  Magellan  after  the
first eight months of operation.

There is a tendency for elevated regions, e.g. the Maxwell Montes  (left
of the data gap at top center) and Aphrodite Terra (along the equator at
right), to show steeper meter-scale slopes than are  typical  of  lower-
lying  areas.  The steeper slopes probably result from disruption of the
surface associated with tectonic activity in these  regions.   Note  the
large  2300-kilometer  (1400-mile)  diameter  circular  feature (Artemis
Chasma) in the lower right of  the  Mercator  image.   This  feature  is
thought  to  have  been caused by a gigantic plume of heated rock rising
from the planet's interior.  The  data  shown  here  were  analyzed  and
projected  at  the Center for Space Research, Massachusetts Institute of
Technology.