Transcripts of magnetometry_101_ipod_lg [silence] [silence] [music] Narrator: You're probably more familiar with magnetic fields than you realize. If you have a compass and a map, you can use the Earth's magnetic field to help you find your way. You've probably also seen what a magnetic field looks like. Drop iron filings around a bar magnet, and the field shows itself as a series of lines. If you take the filings away, you can still get an idea of what the field looks like by flying a tiny compass around the magnet. The compass points in the direction of the magnetic field, allowing you to draw its shape. But how do you find out what a planet's magnetic field looks like? You basically do the same thing. However, instead of flying a simple compass around the planet, NASA scientists use satellites carrying a much more sensitive device called a magnetometer. Mounted far away from the spacecraft, a magnetometer uses electric currents to measure the magnetic field of the planet. By flying this "electronic compass" around the planet, scientists can draw an accurate model of what its magnetic field looks like. And magnetometers have helped scientsts discover more than just the shape of the Earth's magnetic field. Other planets in our solar system, such as Jupiter, have magnetic fields that are similar to ours. The Sun also generates its own magnetic field that affects the entire solar system. But not every planet in our solar system has a magnetic field. For example, we've discovered that, unlike Earth, Mars doesn't have a global magnetic field at all. Instead, it has small pockets of local magnetic fields. But after all is said and done, even with all the advanced technology, the most amazing thing is that we've made all these discoveries using something that's essentially an upgraded compass. [music fading, beeping] [beeping] [silence] [silence]