Lunar Magnetism

[Albertese]

This is probably a simple enough question, but I'm not quite sure where to start to look it up. Actually, I'm a little embarrassed to even need to ask this, but here goes:

Does the moon produce a magnetic field?

In other words, if I found myself with a spacesuit and a compass on the moon and a space vehicle just over the north ridge ready to take me off to more comfortable environs, would I be boned? Or would the compass work like normal?

--Alex

 

[xman]

I'm pretty sure there is no magnetic field on our moon, but there may have been at one point in the ancient past.

http://cubanology.com/Articles/The_Magnetism_of_the_Moon.htm

 

[Kaziarl]

http://en.wikipedia.org/wiki/Moon#Magnetic_field

Magnetic field

Main article: Magnetic field of the Moon

**HOTLINKED IMAGE REMOVED **

Total magnetic field strength at the surface of the Moon as derived from the Lunar Prospector electron reflectometer experiment


The Moon has an external magnetic field of the order of one to a hundred nanotesla—less than one hundredth that of the Earth, which is 30–60 microtesla. Other major differences are that the Moon does not currently have a dipolar magnetic field (as would be generated by a geodynamo in its core), and the magnetizations that are present are almost entirely crustal in origin.[36] One hypothesis holds that the crustal magnetizations were acquired early in lunar history when a geodynamo was still operating. The small size of the lunar core, however, is a potential obstacle to this theory. Alternatively, it is possible that on an airless body such as the Moon, transient magnetic fields could be generated during large impact events. In support of this, it has been noted that the largest crustal magnetizations appear to be located near the antipodes of the giant impact basins. It has been proposed that such a phenomenon could result from the free expansion of an impact generated plasma cloud around the Moon in the presence of an ambient magnetic field.[37]

 

[Asbo Zaprudder]

This is probably a simple enough question, but I'm not quite sure where to start to look it up. Actually, I'm a little embarrassed to even need to ask this, but here goes:

Does the moon produce a magnetic field?

In other words, if I found myself with a spacesuit and a compass on the moon and a space vehicle just over the north ridge ready to take me off to more comfortable environs, would I be boned? Or would the compass work like normal?

--Alex

Nope -- no global dipole field on the Moon.

In daylight on the near side, you could use the Earth to guide you provided you could make out the continents. The stars would be hard to make out against the glare.

In daylight on the far side, you'd have to get into shadow, try and shield out any reflected light, and look at the constellations. Polaris isn't the north star of the Moon, but it would be the right general direction. I think the Moon's north would be near Ecliptic north -- somewhere around the middle of the constellation Draco. The south would be near Canopus.

Edit: or simply use Lunar GPS:

http://www.space.com/businesstechnology/080430-tw-lunar-communication-post.html

 

[Hofner]

In the Apollo lunar landing missions the Rover had special navigational equipment. So they knew which way they were going and how far, it kept track of distance and heading to the LEM.
In other words, the gizmo always remembered where they had parked the LEM.

Robert

 

[Kaziarl]

This is probably a simple enough question, but I'm not quite sure where to start to look it up. Actually, I'm a little embarrassed to even need to ask this, but here goes:

Does the moon produce a magnetic field?

In other words, if I found myself with a spacesuit and a compass on the moon and a space vehicle just over the north ridge ready to take me off to more comfortable environs, would I be boned? Or would the compass work like normal?

--Alex

Nope -- no global dipole field on the Moon.

In daylight on the near side, you could use the Earth to guide you provided you could make out the continents. The stars would be hard to make out against the glare.

In daylight on the far side, you'd have to get into shadow, try and shield out any reflected light, and look at the constellations. Polaris isn't the north star of the Moon, but it would be the right general direction. I think the Moon's north would be near Ecliptic north -- somewhere around the middle of the constellation Draco. The south would be near Canopus.

Edit: or simply use Lunar GPS:

http://www.space.com/businesstechnology/080430-tw-lunar-communication-post.html

Ok, so a magnetic field exists, but its not a dipolar field. So how would a compass act?

 

[Asbo Zaprudder]

In the Apollo lunar landing missions the Rover had special navigational equipment. So they knew which way they were going and how far, it kept track of distance and heading to the LEM.
In other words, the gizmo always remembered where they had parked the LEM.

Robert

Looked it up on Wikipeda (lazy of me) -- http://en.wikipedia.org/wiki/Lunar_rover#Control_and_navigation

"Navigation was based on continuously recording direction and distance through use of a directional gyro and odometer and inputting this data to a computer which would keep track of the overall direction and distance back to the LM. There was also a Sun-shadow device which could give a manual heading based on the direction of the Sun, using the fact that the Sun moved very slowly in the sky."

 

[Asbo Zaprudder]

Ok, so a magnetic field exists, but its not a dipolar field. So how would a compass act?

It would barely move, and, if it did move, it would only point to a local "north" , which you couldn't use to navigate effectively. The largest field strength is on the far side around the rim of the South Pole-Aitken Basin.

http://en.wikipedia.org/wiki/Magnetic_field_of_the_Moon

The diagram doesn't indicate field direction, dip etc.