I'm Nate from Design Squad, and I'm here with... We use magnets every day in speakers, they hold our refrigerator door closed, and they're also used in metal detectors.

[beep]

Today we'll make a detector that can detect a magnetic field. I can't carry any more.

[clattering]

(Maya) Ooh, fuzzy.

(Nate) Yeah. They are iron filings. They stick to... Magnets. Magnets. Exactly.

(Nate) Magnets have a field that they put out that exert a force on metal objects when they're nearby. Magnets aren't the only things that make magnetic fields. In a planet or moon, when huge amounts of fluid, such as molten rock, circulate, they can produce a magnetic field, which is where the magnet's force has an effect. NASA looks for magnetism because it indicates what's inside the planet or moon by understanding its magnetic field. To learn about a planet or moon's magnetic field, NASA sends out spacecraft with devices that could detect them.

The devices are called magnetometers. Right now you are being a magnet field detector, or a magnetometer, 'cause you're sensing the two magnetic fields. I feel them pushing away. Try flipping over the magnet. Whoa! You can feel a force you can't see. Yeah. We're going to use cardboard, cups, string, and metal shards to make our magnetometers. I'll use cardboard to make a frame and then have paper under it. I'm using a cup and cutting out the bottom to make a window.

♪

(Nicholas) I punched holes to put string through them and hold the detector easily.

(Maya) When I move the magnet, the metal moves in the cup.

(Nicholas) Oh, that's cool. You know what else is interesting? Listen.

[rustling]

You can hear the metal moving.

[rustling]

If I hold it too high, you can't see changes, but there's still a little bit. I've hidden magnets underneath the newspaper. We put a grid so they can point out the location. And this is the surface of Mars. Ready to search for magnetic fields on our planetary surface? Yes. Begin.

(Nicholas) I found one at B3.

I found one on H8. (Nate) H8?

[rustling]

Nice. Where else?

[rustling]

For instructions on building your own detector and activities related to NASA's missions, check out the Design Squad website. Accessibility provided by the U.S. Department of Education.