The discussion centers on the existence of localized mini-magnetospheres on Mars, which are more powerful than Earth's global magnetic field. These mini-magnetospheres are caused by concentrated crustal magnetic fields, primarily due to magnetized iron deposits scattered across the Martian surface. The MAVEN satellite is expected to provide further insights into how these crustal fields protect Mars from solar wind. The historical context reveals that Mars once had a molten core that generated a planetary dynamo, but this dynamo ceased functioning over 3.5 billion years ago, leading to the current state of localized magnetic anomalies.
PREREQUISITESAstronomers, planetary scientists, and geologists interested in Martian geology and magnetism, as well as those following the MAVEN mission's contributions to our understanding of Mars.
Delta Force said:The Technical University of Denmark has a page about the Martian magnetosphere in which it mentions the existence of localized mini-magnetospheres on Mars that are more powerful than the global field around Earth (http://www.space.dtu.dk/english/Research/Universe_and_Solar_System/magnetic_field).
Delta Force said:What causes the mini-magnetospheres and how extensive is their strength and coverage of Mars?
Delta Force said:What causes the mini-magnetospheres
DaveThey don't work because there is not one magnetic field on Mars, rather there are dozens. These small fields are powerful, concentrated in the crust, and scattered over the surface of the planet. In their absence, compass needles would lie still; in their presence, they spin, pointing first at one bar magnet, then another. How well these crustal fields protect the planet is a mystery, and one that may be solved soon by the MAVEN satellite, which is on its way to Mars right now.
What we do know is that if a compass ever worked well on Mars, it was over 3.5 billion years ago. Before that time, Mars had a molten core, whose contents constantly churned upward towards the surface. This process of convection permitted cooling of the interior, as well as active volcanism in the highlands and plains. Volcanoes brought iron to the surface, giving Mars its signature color. Iron in the core also moved electrons, which created a planetary dynamo: a device that converts mechanical energy into electric energy. Electric fields generate magnetic fields. Large magnetic fields can provide protection from solar wind for any planet as long its interior maintains a steadfast supply of molten metal.
Large magnetic fields also decay unless maintained. After the first billion years or so, the Martian interior cooled to the point where convection halted. When the iron ceased to flow, the dynamo died. Volcanism declined. The last iron deposits from the interior left their marks as pockets of magnetism, called crustal anomalies, largely sequestered in the southern hemisphere.