Capture Magnet

For whatever reason, the fine red dust on Mars is highly magnetic. When NASA landed the rover Opportunity on the planet a little less than a year ago, one of the things they wanted to examine was why.

They mounted several electro-magnetic discs (capture magnets) on the exterior of the rover and waited for minute amounts of dust to collect on its surface. Because the magnetic fields they generate vary, the dust collects in a striated "bulls-eye" pattern.