"Igneous rocks come from melted rock material, or magma, that lies under Earth's surface" ("How can you tell," n.d.), forming when magma from inside the Earth travels toward the Earth's surface, or a volcano forced it in the form of lava and ash above the Earth's surface, where it cools and crystallizes into rock. Metamorphic rocks, rocks, which may be sedimentary and igneous rocks, changed by intense heat or pressure while they form, come from hot, pressured conditions inside the Earth's crust. At times, these rocks cool and crystallize, into bands of crystals. A researcher may determine if a rock sample is metamorphic by examining the crystals to see if they are arranged in bands ("How can you tell," n.d.).
Images Worth a World of Words
On Mars's surface, magnetic stripes replicate fields in the Earth's sea floors, which some scientes assert could indicate that ancient crustal movements occurred on the Red Planet. ("Plate Tectonics on Mars?" 1999).
The following figure depicts "a map of Martian magnetic fields in the southern highlands near the Terra Cimmeria and Terra Sirenum regions centered around 180 degrees longitude from the equator to the pole" ("Plate Tectonics on Mars?" 1999).
It is where magnetic stripes possibly resulting from crustal movement are most prominent. The bands are oriented approximately east - west and are about 100 miles wide and 600 miles long, although the longest band stretches more than 1200 miles. The false blue and red colors represent invisible magnetic fields in the Martian crust that point in opposite directions. The magnetic fields appear to be organized in bands, with adjacent bands pointing in opposite directions, giving these stripes a striking similarity to patterns seen in the Earth's crust at the mid-oceanic ridges.
Imagine a thin coat of dried paint on a balloon, where the paint is the crust of Mars," explained Dr. Mario Acuna of Goddard, principal investigator on the Global Surveyor magnetometer. "If we inflate the balloon further, cracks can develop in the paint, and the edges of the cracks will automatically have opposite polarities, because nature does not allow there to be a positive pole without a negative countepart." ("Plate Tectonics on Mars?" 1999)
Plate Tectonics on Mars?" 1999). PHOTO CREDIT: NASA, Jack Connerney, Mario Acuna, Carol Ladd
Plate Tectonics on Mars?" 1999)
Info in Red not yet rewritten Apr. 29, 1999: NASA's Mars Global Surveyor has discovered surprising new evidence of past movement of the Martian crust, suggesting that ancient Mars was a more dynamic, Earth-like planet than it is today.
Scientists using the spacecraft's magnetometer have found banded patterns of magnetic fields on the Martian surface. The adjacent magnetic bands point in opposite directions, giving these invisible stripes a striking similarity to patterns seen in the crust of Earth's sea floors.
An artist's concept comparing the present day magnetic fields on Earth and Mars. Earth's magnetic field is generated by an active dynamo - a hot core of molten metal. The magnetic field surrounds Earth and is considered global (image B, below). The various Martian magnetic fields (image a, above) do not encompass the entire planet and are local. The Martian dynamo is extinct, and its magnetic fields are "fossil" remnants of its ancient, global magnetic field. IMAGE CREDIT: NASA Mario Acuna, Jack Connerney, Chris Meaney
The bands of magnetized crust apparently formed in the distant past when Mars had an active dynamo, or hot core of molten metal, which generated a global magnetic field. Mars was geologically active, with molten rock rising from below cooling at the surface and...
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