They have been testing a laser system for measuring lunar dust and soil kicked up by rocket exhausts, and while using precipitation as a substitute to calibrate the laser, they found they could measure the average size of raindrops passing through it.
But such is their persistence that they can also be found in soil, sediment, food, air and house dust, and 97% of Americans have detectable levels in their bodies.
The government says it makes no sense to allow much of the country's best soil to lie fallow while farmers struggle to squeeze a living from minuscule, dust-blown fields.
At the start of this new drama by Shane Carruth, a botanist brushes blue dust from a plant and makes infusions and capsules from worms that he sifts from its soil.