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1993-05-03
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Contact: Jim Doyle
FOR RELEASE FRIDAY, AUG. 30, AND THEREAFTER
The Magellan spacecraft, mapping the surface of Venus with
imaging radar, has discovered the longest channel known in the
solar system, a project spokesman at NASA's Jet Propulsion
Laboratory said.
The channel crosses the plains of Venus for 6,800 kilometers
(4,200 miles), longer than the Nile River, the longest river on
Earth, said Project Scientist Dr. Steve Saunders.
"The very existence of such a long channel is a great
puzzle," Saunders said. "If the long channel were carved by
something flowing on the surface the liquid must have had unusual
properties."
Saunders said it may have been some material that was near
its freezing or melting point at the average surface conditions
of Venus -- surface pressure 90 times that of Earth and a
temperature of 864 degrees Fahrenheit.
"There are no very likely candidates for a liquid," Saunders
said. "Lava, even very high temperature types, would need to have
a very high rate of flow to go so far. This is not consistent
with the uniform narrow channel morphology."
He said the channel is very uniform in width, averaging
little more than one mile across (1.8 kilometers). "It follows a
sinuous, smoothly-curving course that can be traced continuouslyon the surface just west of Atla Regio northward nearly to the
large basin called Atalanta Planitia."
A few segments of the channel were mapped in 1984 by the
Soviet Venera 15 and 16 orbiters which carried radar capable of
resolving features down to 1 to 2 kilometers (0.6 to 1.2 miles).
With the higher resolution of Magellan, about 400 feet (120
meters) the channel can be traced unbroken along its course,
Saunders said.
Similar channels have been seen on many of the plains
surfaces in other parts of Venus, he said. In some cases the
channels terminate in lava flows, indicating that they probably
were carved out by molten lava from a volcanic eruption. No
similar features are now known on Earth, although lava channels
are known to have formed on Earth billions of years ago.
"The challenge of understanding the origin of this channel
will lead to better understanding of planetary geological
processes and many related fields such as material properties and
fluid mechanics," Saunders said.
Magellan is currently mapping the south pole of Venus. In
the first 243-day mapping cycle which ended May 15, the
spacecraft mapped 84 percent of the planet. In its second cycle,
it has mapped for the second time a 600-mile wide strip and that
section of Venus is being examined to see if any changes occurred
from one cycle to the other.
Preliminary analysis of that data has so far revealed no
changes occurring on the surface of Venus between mapping cycles.
Magellan now has its high-gain antenna turned to the right
as it maps long strips of the surface. During the first mapping
cycle the side-looking radar was turned to the left. The antenna
was turned to the right to map the south pole.
Many of the same features that were imaged from the left
during the first cycle are being imaged now from the new angle,
which will permit investigators to get more accurate measurements
and also will provide three-dimensional views of some features.
The project said that because the spacecraft is currently in
the sun during most of each orbit, measures are being taken to
prevent temperatures from getting too high. A command sequence
went into effect Thursday which will hide the spacecraft behind
its large antenna twice in each orbit.
The Jet Propulsion Laboratory manages the Magellan project
for NASA's Office of Space Science and Applications, Washington,
D.C.
#1387 8/29/91jjd
Editors: The above release is illustrated by a set of
Magellan radar images of Venus. They will be available at the
Public Information Office, JPL.