This is an electron microscope image of a dust particle rounded by eolian transport. It originated in the Sahara desert and was found in 7.2 million year old sediments in Greece. Disclaimer ...

Its contents: 122 grams of dust and rock from asteroid Bennu ... They examined barely visible grains of Bennu using the transmission electron microscope of the Schwiete Cosmochemistry Laboratory ...

This story appears in the July 2013 issue of National Geographic magazine. The dust speck had been plucked from the tail of a comet more than 200 million miles away. Now, under an electron ...