Crustal dichotomy and remnant magnetism

Crustal dichotomy and remnant magnetism

. The magnetic fields that are currently on Mars are located mainly in the older, heavily cratered southern hemisphere, below the dichotomy boundary (solid line) that separates the highlands (bottom) from the younger, smoother lowland plains in the north (top). A global magnetic field, which no longer exists, was probably imprinted in the highland rocks when they formed more than 4.0 billion years ago, before the lowland plains existed. Hellas and Argyre are two deep impact craters blasted out of the Martian surface after the global magnetism was no longer present. The blue and red colors represent magnetic fields pointing in opposite directions, in and out of the planet, as measured by an instrument aboard the Mars Global Surveyor. They form a banded pattern shown in greater detail in Fig. 8.26. (Courtesy of NASA, JPL and GSFC.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University