What is dust made of? - Michael Marder

Meet Dermatophagoides farinae.

Crawling around on eight legs,

this creature has no eyes to appreciate the kaleidoscope of colors around her.

She relies on her extraordinary sense of smell

to lead her to food and safe places to lay eggs.

And she’s smaller than a pinhead.

Dermatophagoides farinae is a dust mite.

Less than a tenth the size of an ant,

a dust mite’s whole world is contained in the dusty film under a bed

or in a forgotten corner.

This realm is 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?

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.

Dust mites eat animal dander,

human skin,

and some fungi.

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.

The combination of these elements can be as unique as a fingerprint.

In Spain, where the land is rich in carbonate materials,

dust contains 20 times as much calcium as dust in Nigeria,

where the geology is quite different.

After a particularly violent storm,

scientists identified dust from the Sahara Desert

thousands of miles away in London,

based on its specific composition.

In the future,

we may be able to pinpoint the origins of dust samples even more specifically,

down to a particular neighborhood or even house -

something that may be of great help for forensic specialists.

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.

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.