MadSci Network: Astronomy
Query:

Re: Why does the moon have less of a magnetic field than the earth.??

Date: Tue Nov 16 12:20:25 1999
Posted By: Denise Kaisler, Grad student, Astronomy, UCLA, Division of Astronomy
Area of science: Astronomy
ID: 939995666.As
Message:

The answer lies in the different compositions of the Earth and Moon. Our
home planet is made up of four different layer: crust, mantle, liquid
outer core, and solid inner core. The Earth's magnetic field is produced by
convection currents in the outer core. 

The moon, from what we can tell by seismic recorders left there by
astronauts, has a very different structure. Although it also has a crust, a
solid iron core, and a mantle-analogue called the lithosphere, the moon's
outer core is not fully liquid. It is described as "plastic". This isn't to
say that there are huge deposits of Hefty bags in the moon's interior -
just that the matierial there has a higher viscosity (resistance to flow)
than a regular liquid. So the moon's outer core is halfway between a liquid
and a solid and it doesn't move around like the Earth's outer core does, so
It can't keep up a strong magnetic field. Although the moon did have a
magnetic field to begin with (we know this because we've examined the
crystal structure in moon rocks), magnetic fields tend to fade over time
unless there is something replenishing them. That process doesn't work on
the moon so these days it has no magnetic field.




Current Queue | Current Queue for Astronomy | Astronomy archives

Try the links in the MadSci Library for more information on Astronomy.



MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci


MadSci Network, webadmin@www.madsci.org
© 1995-1999. All rights reserved.