Consider dust. We all see it build up in our house if we don’t dust enough, and really who has time for that? This is nothing compared to the outside world, however. 

Growing up, it always mystified me that enough dust and dirt fell out of the air to somehow, over time, completely bury ancient civilizations. As an adult, I now know that plants are taking nutrients from the air and soil and converting them into structures fully capable of burying my flower beds in three inches of leaves. I know dust blown from deserts and ash exploded out of volcanoes can travel the world, layering grit on every surface in depths ranging from dustings to many inches. What I didn’t know, until today, was that 5,200 tons of space grit make it to the surface of our world every year. 5,200 tons. 

We knew, based on the number of streaks seen across the sky, that our world is regularly hit by a lot of space rocks. To determine how much material actually strikes the planet, researcher Jean Duprat traveled to the Franco-Italian Concordia station in the heart of Antarctica and collected samples from the snow in a site where there would be a near absence of terrestrial dust. By assuming that what was collected in Antarctica is representative of what fell everywhere in the world, they were able to calculate the worldwide dustfall of dust from space. 

The grains they found ranged from 30 to 200 micrometers, and it appears that 80% of the material comes from comets, with the remainder from asteroids. So now you know, when your car is filthy, you can blame air pollution, pollen, ash, dust, and space dust.

More Information

CNRS press release

“The micrometeorite flux at Dome C (Antarctica), monitoring the accretion of extraterrestrial dust on Earth,” J. Rojas et al., 2021 April 15, Earth and Planetary Science Letters