What is dust made of?

Dust lives right under our noses, but from our perspective, the tiny specks of brilliant color blend together into a nondescript grey. What are these colorful microscopic particles?

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What distinguishes the dust in your house from, say, sand on a beach is that it is a mixture of many different ingredients. It can contain grains of sand, dead skin cells, tiny hairs and threads, animal dander, pollen, manmade pollutants, minerals from outer space, and, of course, dust mites. 

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We shed dead skin cells constantly, and wherever we live, they mix into the household dust. The same goes for our pets: their dander and hairs enter the mix, as do tiny pieces of thread and cotton fibers from our clothes. These components make every household’s dust a unique blend of bits from its particular inhabitants. Household dust also contains substances that blow in from the wider world. Depending on the local geology, finely ground quartz, coal, or volcanic ash might enter the air as atmospheric dust, along with pollen and fungal spores. Industrial activities also contribute cement powder, particles from car tires, and other chemicals to the airborne mix.

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In addition to markers of humans, animals, and landscapes, dust also contains particles from further afield. When a star explodes in a distant galaxy, super hot gases vaporize everything nearby. Then, the dust settles; minerals condense out of the gas. Floating out there between planets and galaxies, this extraterrestrial dust contains tiny pieces of extinguished stars and the building blocks of future celestial bodies. Every year, tens of thousands of tons of cosmic dust lands on Earth and mingles with terrestrial minerals. This blend of chemicals, minerals, and intergalactic particles settles out of the air onto surfaces in our homes, mixing with the detritus of each house’s occupants. Stars explode, mountains erode, and buildings, plants, and animals are all slowly but surely pulverized into fine grey powder. 

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We’re all destined to become dust, but it’s also possible that we came from it. Interstellar dust has been found to carry organic compounds through space. It’s possible that billions of years ago, some of these cosmic particles were the seed of life on our little blue planet.

From the TED-Ed Lesson What is dust made of? – Michael Marder

Animation by Mette Ilene Holmriis