home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Space & Astronomy
/
Space and Astronomy (October 1993).iso
/
pc
/
images
/
venus_1
/
gredr.txt
< prev
next >
Wrap
Text File
|
1993-07-13
|
2KB
|
34 lines
MAGELLAN PROJECT OFFICE
MIT ID: GREDRP.1;2
JPL ID: P-40348
Date: 6/15/92
These images show the distribution of radar reflection coefficient
(reflecting efficiency) of the Venus surface when viewed from directly
overhead by the Magellan altimeter. The lightest shades locate areas
having the highest values of normal-incidence reflectivity (as high as
70 percent in places), while darker shades indicate areas of low
reflection efficiency. 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 higher values of reflectivity than are typical of
lower-lying areas. The highest values (greater than 30 percent) are
puzzling to understand. On a cooler planet such as Earth or Mars, water
or ice might explain the observations, but at the 470-degree-Celsius
temperature of the Venus surface, neither can be present. Some theories
require the presence of minerals such as iron pyrites; others suggest a
material, as yet unidentified, that has extremely low electrical loss.
The data shown here were analyzed and projected at the Center for Space
Research, Massachusetts Institute of Technology.