112 lines
4.2 KiB
Plaintext
112 lines
4.2 KiB
Plaintext
SUBJECT: VIKING - MARS QUAKES FILE: UFO3344
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Message number 2413 in "MUFON_WIRE"
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Date: 11-08-92 1:38
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From: Don Allen
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To: All
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Subj: Viking - Mars Quakes
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** Forwarded from Usenet **
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---------------------------------------------------------------------
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Article 153 of alt.sci.planetary:
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Newsgroups: sci.space,sci.astro,alt.sci.planetary,sci.geo.geology
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From: baalke@kelvin.jpl.nasa.gov (Ron Baalke)
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Subject: Viking Photos Shows Evidence of Marsquakes
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Message-ID: <1992Nov6.234127.4444@elroy.jpl.nasa.gov>
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News-Software: VAX/VMS VNEWS 1.3-4
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Keywords: Viking, Mars, JPL, USGS, MESUR
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Sender: news@elroy.jpl.nasa.gov (Usenet)
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Nntp-Posting-Host: kelvin.jpl.nasa.gov
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Reply-To: baalke@kelvin.jpl.nasa.gov
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Organization: Jet Propulsion Laboratory
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Date: Sat, 7 Nov 1992 07:40:54 GMT
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Lines: 103
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Paula Cleggett-Haleim
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Headquarters, Washington, D.C. November 6, 1992
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(Phone: 202/358-1547)
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Jim Doyle
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Jet Propulsion Laboratory, Pasadena, Calif.
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(Phone: 818/354-5011)
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RELEASE: 92-198
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VIKING PHOTOS SHOW MARS MAY EXPERIENCE FREQUENT QUAKES
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Mars was once very active tectonically and may still be
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shaken by quakes daily, according to scientists using NASA's
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Viking Orbiter photos of the red planet's surface.
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In a science paper published today, Drs. Matthew
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Golombek, W. Bruce Banerdt and David M. Tralli of the Jet
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Propulsion Laboratory and Dr. Kenneth L. Tanaka of the U.S.
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Geological Survey said Mars is more seismically active than
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the moon, but less so than Earth.
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"Because Mars is smaller than Earth, little more than
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half the size, a magnitude 6 quake on Mars would have 10
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times the effect it would on Earth," Golombek said.
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Marsquakes of that magnitude may occur about once every
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4 and a half years, he said. A marsquake of about magnitude
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4, however, might happen somewhere on the planet once a month
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on an average. Yet, a quake of magnitude 4 would be
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detectable throughout the planet, again because of its size
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and presumed structure.
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Tectonic features on Mars are found mostly around the
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Tharsis region, a large volcanic plateau with associated
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features that cover the entire western hemisphere of the
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planet.
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Tectonism in that region occurred mainly during two
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periods in the planet's history -- the earliest possibly as
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long ago as 4-billion years and the most recent ending
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possibly less than one-billion years ago.
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Features that formed during the first seismic period
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include many narrow graben or long ditch-like or trough
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features with faults along their sides. Also formed at that
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time was a system of concentric wrinkle ridges, larger graben
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and rifts, and the deep rift valleys of Mars' great 1,860-
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mile-long (3,000-kilometer) canyon, the Valles Marineris.
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During the second period, tectonism caused an enormous
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set of radial grabens that extend up to thousands of
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kilometers from the center of the plateau and rift zones of
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Valles Marineris, along with other prominent features.
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Tectonism and seismic activity have decreased from the
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earlier period to the present, Golombek said, as would be
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expected if the seismic activity is governed by simple
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cooling of the lithosphere -- the rigid outer crust and upper
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part of the mantle -- of the planet.
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The scientists said that while Mars is less seismically
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active than Earth, their studies predict that about two
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marsquakes of magnitude 5 or greater occur per year, about a
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hundred quakes of magnitude 3 or greater occur per year.
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"That is a promising prospect for seismological
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investigations on future missions to Mars," Golombek said.
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Golombek is the Project Scientist for the Mars
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Environmental Survey (MESUR) project which would place a
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network of landers, each with a seismometer, in different
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locations on the Martian surface. Recordings of marsquakes
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by seismometers at different locations will help determine
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the internal structure of the red planet.
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