Tons of Invisible Asteroid and Comet Dust Falls on Us Every Year

Some 10,000 grand pianos’ worth of space dust lands on Earth each year, according to a new paper published in Earth & Planetary Science Letters.

The finding emerged from six French National Scientific Research Center expeditions in Antarctica, which spanned 20 years at the extremely isolated Concordia Research Station. Concordia made a great venue for spotting extraterrestrial dust because of the minimal amounts of Earth dust there and, despite being in Antarctica, a low rate of snow accumulation.

You don’t see this dust because it’s minuscule, about 1/50th the size of a grain of sand at most. But annually, the researchers reported, 5,200 tons of the stuff falls from the heavens from a variety of cosmic sources. The dust is most likely shed by asteroids or comets and is the biggest source of space material to Earth, according to the researchers.

Under the microscope, the particles look like forbidden bits of interplanetary cotton candy. They were collected in what can only be considered the 21st-century version of gold prospecting: The research team collected big buckets of snow, melted it, and then sieved the water for anything that fell from space.

From the 2,000-odd bits and bobs from space they managed to find, the team then extrapolated the amount of micrometeoritic mass that falls to Earth each year. Most of that stuff is unobtainable, lost in the hubbub of earthly activity, human and otherwise. It’s the same reason the best meteorites for chemical analysis are those found on frozen lakes or deserts—they’re most devoid of the contamination us lifeforms bring.

The researchers also conducted a chemical analysis to determine the origin of the space dust. They found that the primary source (80%) of the matter could be attributed to comets. But the researchers also surmised that there’s probably about 15,000 tons of dust that orbits near us before entering Earth’s atmosphere. The researchers wrote that some of that dust may not come down to roost.

Whatever the case, the implications of this dust are palpable. Since it comes from meteorites, there’s a chance that the dust could fill holes in our understanding of carbonaceous chondrites, the meteorites as ancient as the solar system that are seen as major candidates bringing water to young Earth.

Since this 5,200-ton dust estimate is annual, it also theoretically means a steady stream of new meteoritic data can be found on Antarctica’s frozen sprawl. Researchers just need to keep sieves at the ready.