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Lava Plains and Voleanoes (P-38724)
This image - a three-dimensional map of the surface of Venus - is
a combination of Magellan synthetic aperture radar data and radar
altimetry. The perspective viewpoint is located northeast of
Western Eistla Regio at an elevation of 7.5 kilometers (4.6
miles).
At the left, just below the horizon, is the volcano Gula Mons, 3
kilometers (1.8 miles) high, located at approximately 22 degrees
north latitude, 359 degrees east longitude. Lava flows extend for
hundreds of kilometers to the base of Gula Mons across the
fractured plains shown in the foreground. Sif Mons, a volcano with
a diameter of 300 kilometers (180 miles) and a height of 2
kilometers (1.2 miles), is seen at the right. The distance between
Sif and Gula is approximately 730 kilometers (453 miles). Sif and
Gula may have formed over a region of hot material rising from
deep within the planet - the same process responsible for forming
the Hawaiian Islands on Earth.
For this image, rays cast in a computer intersect the surface to
create a three-dimensional perspective view. Features are
exaggerated to facilitate scientific analysis; the topographic
relief shown is approximately 20 times greater than the actual
terrain. The color approximates what would be seen by the human
eye at the surface of Venus under daytime conditions and is based
on color images recorded in the early 1980s by the Soviet Venera
13 and 14 landers.
The Magellan Mission
Magellan, a NASA spacecraft mission to map the surface of
Venus with imaging radar, was launched on 4 May 1989 aboard the
Space Shuttle Atlantis. After a 15-month cruise, the spacecraft
went into orbit around Venus on 10 August 1990 and began mapping.
Magellan's synthetic aperture radar (SAR) penetrates the dense,
sulfurous clouds that perpetually shield the planet's surface,
producing one image "swath" with each orbit of the spacecraft. One
mapping cycle is completed with each Venus rotation, which is
equivalent to 243 Earth days.
The spacecraft successfully completed its first mapping cycle and
primary mission on 15 May 1991 after 1,680 orbits of Venus. The
second cycle followed immediately; the third cycle began on 1
January 1992. Designed to map at least 70 percent of Venus,
Magellan covered more than 97 percent of Venus' surface during the
first three cycles. Magellan continues to study the planet,
looking for evidence of recent volcanic eruptions and other
surface changes. A fourth cycle, beginning 15 September 1992, is
dedicated to a global gravity survey, which will help scientists
determine the internal structure of Venus.
Magellan's high-resolution SAR has revealed a planet dominated by
volcanic processes. The surface is characterized by volcanic
domes, rift valleys, extensive plains and complex faults. At least
85 percent of Venus is covered by volcanic rock - mostly lava
flows that form the vast plains. Much of the remaining surface
comprises mountainous areas that appear to have been repeatedly
deformed by geologic activity. Analyzing Magellan's enormous
wealth of information about Venus will be a challenge to
scientists for years to come. The data will improve our
understanding of all four terrestrial planets - Mercury, Venus,
Earth and Mars - through comparative planetology studies.
The Magellan project is managed for NASA by the Jet Propulsion
Laboratory (JPL) of the California Institute of Technology. The
prime contractors were Martin Marietta Astronautics Group in
Denver, Colorado, and Hughes Aircraft Company in El Segundo,
California, who built the spacecraft and the radar system,
respectively.
NASA - National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, California