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Home Science 5,200 Tons of Extraterrestrial Dust Rain Down on Earth Every Single Year

5,200 Tons of Extraterrestrial Dust Rain Down on Earth Every Single Year

We’ve identified for some time that Earth is beneath a relentless rain of area mud, and that it is copious. Given its microscopic dimension, nonetheless, it has been very exhausting to acquire an correct estimate of the amount.


Such micrometeorites aren’t any greater than a fraction of a millimeter, shed like area dander from passing comets and asteroids.

After twenty years of amassing the stuff in Antarctica, a world group of scientists now has a quantity: round 5,200 tons of micrometeorites smaller than 700 micrometers (0.7 millimeters), yearly.

This, they mentioned, makes micrometeorites the most important supply of extraterrestrial materials delivered to Earth’s floor.

It’s truly fairly an achievement. Earth’s environment is crammed with mud, of all types. A research final 12 months discovered that round 17 million metric tonnes of coarse mud is blowing round within the environment at any given time.

To reduce this ‘background’ mud, the group turned to Antarctica on the Concordia station at Dome C. Terrestrial mud is just about absent there, and the snow accumulation price is low, which implies the snow that’s already there might be melted to acquire the speed of micrometeorite fall within the area.

micrometeoritesMicrometeorites from Antarctica. (Rojas et al., EPSL, 2021)

In six expeditions over the course of 20 years, the researchers did simply that. They recognized a complete of 1,280 unmelted micrometeorites and 808 cosmic spherules (melted area rock) beneath 350 micrograms in mass, which allowed them to calculate the speed at which these particles rain down on the floor.

According to their calculations, extrapolated throughout the globe and assuming that the rain is evenly distributed, roughly 1,600 tons of micrometeorites and three,600 tons of cosmic spherules attain the floor yearly. That’s a complete of 5,200 tons yearly.


The subsequent half of the analysis was an evaluation of the mud to find out its origin, based mostly on the density of the grains. Lower density and better porosity recommend a cometary origin, and better density and decrease porosity recommend a meteoritic origin.

From this, the group extrapolated that roughly 80 p.c of the cosmic mud that reaches Earth’s floor is ejected from comets as they zoom by on their orbital journeys – a quantity in line with earlier estimates of the cometary enter to area mud on Earth.

The group’s fashions, nonetheless, additionally confirmed that the overall mass of cosmic mud enter earlier than atmospheric entry is round 15,000 tons. The motive for this discrepancy is not clear, however there are a pair of main choices.

One is {that a} important proportion of the mud evades our capability to detect it. Another is that some of the mud is eliminated previous to atmospheric entry. A 3rd may very well be that there’s considerably much less mud within the area round Earth than we predict there’s.

Figuring out which of these it’s, the researchers mentioned, might assist us higher constrain the position of cosmic mud in delivering water molecules and carbon to Earth, within the early days of the Solar System – in flip offering items of the puzzle that’s the emergence of life itself.

The group’s analysis has been revealed in Earth and Planetary Science Letters.


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