This composite image shows particles adhering to magnetic target arrays on the Pathfinder lander. Each array consists of five magnets that increase in magnetic filed strength as seen from left to right. The red material forming a bull's-eye pattern on the arrays is magnetic Martian dust deposited from the atmosphere. An increase in magnetic dust deposition from Sol 10 to Sol 66 is clearly evident. By analyzing the patterns of dust on the various magnets, scientists are able to measure the dust's magnetic strength and infer its composition.
