1999 SPACE SCIENCE VIDEOTAPES |
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Tape Title | Record ID | Date Produced | TRT: |
Synoposis |
| MAGNETIC STRIPES PRESERVE RECORD OF ANCIENT MARS | G99-035 | 04/29/99 | 00:13:43 | More evidence has emerged that ancient Mars was a more dynamic, Earth-like planet than it is today, based on observations by NASA's Mars Global Surveyor (MGS) mission. Scientists using the spacecraft's magnetometer instrument have discovered surprising evidence for past movement of the Martian crust in the form of banded patterns of magnetic fields on the Martian surface. |
TAPE CONTENTS: |
| ITEM (1): MAGNETIC STRIPES ON MARS - Scientists have discovered surprising evidence for past movement of the Martian crust in the form of banded patterns of magnetic fields on the Martian surface. The first sequence begins with the Martian surface with data from the Mars Global Surveyor overlaid. The alternating magnetic stripes can be seen in red and blue. The final image shows an interpolated view of the data.
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| ITEM (2): OLDEST MARS CRUST - The map also identifies an area in the southern highlands near the Terra Cimmeria and Terra Sirenum regions as the oldest surviving unmodified crust on Mars. This area on Mars, centered around 180 degrees longitude from the equator to the pole, is where the magnetic stripes are most prominent.
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| ITEM (3): OBSERVING THE MAGNETIC STRIPES - The observations were made with the spacecraft's magnetometer/electron reflectometer instrument.
The magnetic fields in adjacent bands point in opposite directions, giving these invisible stripes a striking similarity to patterns seen in the crust of Earth's sea floors. Like a Martian tape recorder, the crust has preserved a fossil record of the magnetic field directions that prevailed at different times in the ancient past. |
| ITEM (4): EVIDENCE FOR MOVEMENT OF THE MARTIAN CRUST - On the Earth, the sea floor slowly spreads apart at mid-oceanic ridges as new crust is extruded from Earth's hot interior. The resulting stripes carry a frozen record of the past few hundred million years of Earth's magnetic history, a finding that validated the once controversial theory of plate tectonics.
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| ITEM (5): VIOLENT IMPACTS ERASE THE MAGNETISM - The map reveals that the northern regions are largely free of magnetism, indicating the northern crust formed after the dynamo died. One possibility is that later asteroid impacts followed by volcanic activity heated and shocked large areas of the northern crust, obliterating any local magnetic fields and smoothing the terrain.
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| ITEM (6): MAGNETIC FIELD FLIP CREATES "STRIPES" - The bands of magnetized crust apparently formed in the distant past when Mars had an active dynamo which generated a global magnetic field. Periodically, conditions in the Mars dynamo changed and the global magnetic field reversed direction. The oppositely directed magnetic field was then frozen into subsequent, freshly extruded crust.
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| ITEM (7): SERENDIPITY FROM EXTENDED AEROBRAKING - The observations of the so-called magnetic stripes were made possible because of Mars Global Surveyor's special aerobraking orbit, which was extended due to a problem with a solar panel on the spacecraft. The lowest point of each elliptically shaped orbit dipped below the planet's ionosphere, allowing the magnetometer to obtain better-than-planned regional views of Mars.
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| ITEM(8): MARS AND EARTH HAVE DRAMATICALLY DIFFERENT MAGNETIC FIELDS - The Earth's hot core of molten metal, or dynamo creates a global magnetic field. As Mar's hot core cooled, the dynamo ceased and the global magnetic field of Mars vanished. However, a fossilized record of the magnetic field was preserved in the crust and detected by the MGS instrument.
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| ITEM (9): PLATE TECTONICS ON EARTH - The Earth's surface is made up of tectonic plates formed from continental or oceanic crust and the top of the mantle. Convection in the mantle results in new crust being formed at the mid-oceanic ridges, which pushes the plates apart and drives the movement of the continents. Volcanoes, earthquakes, mountains and trenches are a few of the key features this produces.
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| ITEM (10): EARTH'S MAGNETIC FIELD PROTECTS - The Earth's global magnetic field shields it from fast-moving, electrically charged particles from the sun which are an impediment to life. |
| ITEM (11): VOLCANO B-ROLL - Volcanoes on Earth.
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| ITEM (12): MARS FLYOVER - Background animation of Mars from JPL's "Mars the Movie."
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| ITEM (13): B-ROLL SCIENTISTS IN LAB - Dr. Mario Acuna and Dr. Jack Connerney discuss the magnetometer findings.
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| ITEM (13): INTERVIEW EXCERPTS - DR. MARIO ACUNO, NASA GODDARD SPACE FLIGHT CENTER, GREENBELT, MARYLAND
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| ITEM (13): INTERVIEW EXCERPTS - DR. JACK CONNERNEY, NASA GODDARD SPACE FLIGHT CENTER, GREENBELT, MARYLAND
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