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.
