The Moon's Magnetosphere

Unlike the Earth, which has a protective shield around it called the magnetosphere, the surface of the moon is not protected from the solar wind. This picture shows the magnetosphere surrounding the Earth, with the Earth a small object in the center.

A planet's magnetosphere is provided through its magnetic field. To create a magnetic field, a planet or moon must have magnetic material such has iron, which is warm enough to move around to form currents within the planet.

Over time planets and moons freeze completely through. It is possible that the moon has little magnetic field because it's iron core has frozen solid. Further exploration of the Moon through missions such as Lunar Prospector will help scientists figure out what happened to the Moon's magnetic field.