Re: New Map Provides More Evidence Mars Once Like Earth-like

Bravo George... can you now ad that man comes from Mars... and once in your
life times, you would have told words of trutht....

Good boYYY GEORGE...

"George" <george@xxxxxxxxxxxxxxxxxxxxx> a écrit dans le message de news:
mw05f.493830$xm3.92758@xxxxxxxxxxxx
> http://www.nasa.gov/centers/goddard/news/topstory/2005/mgs_plates.html
>
> Cynthia O'Carroll
> Goddard Space Flight Center, Greenbelt, Md. October 12, 2005
>
> New Map Provides More Evidence Mars Once Like Earth
>
> NASA scientists have discovered additional evidence that Mars once
> underwent plate tectonics, slow movement of the planet's crust, like the
> present-day Earth. A new map of Mars' magnetic field made by the Mars
> Global Surveyor spacecraft reveals a world whose history was shaped by
> great crustal plates being pulled apart or smashed together.
>
> Scientists first found evidence of plate tectonics on Mars in 1999.
> Those initial observations, also done with the Mars Global Surveyor's
> magnetometer, covered only one region in the Southern Hemisphere. The
> data was taken while the spacecraft performed an aerobraking maneuver,
> and so came from differing heights above the crust.
>
> This high resolution magnetic field map, the first of its kind, covers
> the entire surface of Mars. The new map is based on four years of data
> taken in a constant orbit. Each region on the surface has been sampled
> many times. "The more measurements we obtain, the more accuracy, and
> spatial resolution, we achieve," said Dr. Jack Connerney,
> co-investigator for the Mars Global Surveyor magnetic filed
> investigation at NASA's Goddard Space Flight Center, Greenbelt, Md.
>
> "This map lends support to and expands on the 1999 results," said Dr.
> Norman Ness of the Bartol Research Institute at the University of
> Delaware, Newark. "Where the earlier data showed a "striping" of the
> magnetic field in one region, the new map finds striping elsewhere. More
> importantly, the new map shows evidence of features, transform faults,
> that are a "tell-tale" of plate tectonics on Earth." Each stripe
> represents a magnetic field pointed in one direction­ -- positive or
> negative­ -- and the alternating stripes indicate a "flipping" of the
> direction of the magnetic field from one stripe to another.
>
> Scientists see similar stripes in the crustal magnetic field on Earth.
> Stripes form whenever two plates are being pushed apart by molten rock
> coming up from the mantle, such as along the Mid-Atlantic Ridge. As the
> plate spreads and cools, it becomes magnetized in the direction of the
> Earth's strong global field. Since Earth's global field changes
> direction a few times every million years, on average, a flow that cools
> in one period will be magnetized in a different direction than a later
> flow. As the new crust is pushed out and away from the ridge, stripes of
> alternating magnetic fields aligned with the ridge axis develop.
> Transform faults, identified by "shifts" in the magnetic pattern, occur
> only in association with spreading centers.
>
> To see this characteristic magnetic imprint on Mars indicates that it,
> too, had regions where new crust came up from the mantle and spread out
> across the surface. And when you have new crust coming up, you need old
> crust plunging back down­ -- the exact mechanism for plate tectonics.
>
> Connerney points out that plate tectonics provides a unifying framework
> to explain several Martian features. First, there is the magnetic
> pattern itself. Second, the Tharsis volcanoes lie along a straight line.
> These formations could have formed from the motion of a crustal plate
> over a fixed "hotspot" in the mantle below, just as the Hawaiian islands
> on Earth are thought to have formed. Third, the Valles Marineris, a
> large canyon six times as long as the Grand Canyon and eight times as
> deep, looks just like a rift formed on Earth by a plate being pulled
> apart. Even more, it is oriented just as one would expect from plate
> motions implied by the magnetic map.
>
> "It's certainly not an exhaustive geologic analysis," said Dr. Mario
> Acuña, principal investigator for the Mars Global Surveyor magnetic
> filed investigation at Goddard Space Flight Center. "But plate tectonics
> does give us a consistent explanation of some of the most prominent
> features on Mars."
>
> Results were published in the Oct. 10 edition of the Proceedings of the
> National Academy of Science.
>
> Other scientists working on the project included Dr. G. Kletetschka of
> the Catholic University of America, Washington, DC, and Goddard Space
> Flight Center; Dr. D.L. Mitchell and Dr. R.P. Lin of the University of
> California at Berkeley; and Dr. H. Reme of the Centre d'Etude Spatiale
> des Rayonnements in France. Dr. Acuña leads the international team that
> built and operates the Mars Global Surveyor magnetometers. The Jet
> Propulsion Laboratory, a division of the California Institute of
> Technology in Pasadena, manages the mission for NASA's Science Mission
> Directorate in Washington.
>
>
>


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