Space dust bunnies

The Earth is collecting dust. That’s the pronouncement from French scientists who set up an Antarctic experiment to look for micrometeorites that collide with Earth, survive the planet’s atmosphere, and land on the surface. In an April 15 entry into Earth & Planetary Science Letters, the team estimated that roughly 5,700 tons (or 5,200 metric tons) of extraterrestrial dust falls to Earth in any given year.

Researchers conducted the experiment at the French and Italian facility Concordia Station. Nearly 700 miles inland from the Antarctic coast, the Concordia location offered something almost no other place on Earth could. Far away from humans, plants and animals, it’s one of the few places on the planet with nearly zero terrestrial dust.

That meant any dust that fell onto the collection site on the Antarctic Plateau had to come from space. Sorbonne University cosmochemist Jean Duprat led a team that dug up huge amounts of snow at one location until they reached a layer that accumulated in 1995, the year work began towards the international research station. Below that, the snow would be clean of human interference.

The team used carefully cleaned tools to remove hundreds of pounds of older snow for analysis. After melting it, the scientists strained the water through a fine sieve, looking for alien objects. The team identified more than 2,000 particles they believed fell from space ranging from a thousandth of an inch to a hundredth of an inch in size.

Duprat’s team said about 80 percent of the extraterrestrial objects came from comets, icy chunks of rock that are sometimes visible from Earth due to their unusual orbits around the Sun. Comet tails are made up of dust particles and gases. Sometimes the particles released by comets collide with a larger celestial body, like the Earth. Researchers estimated that another 20 percent of the fine particles discovered in the Antarctic snow came from dust sluffed off of larger asteroids.

To calculate the amount of alien dust that reaches Earth each year, the French scientists assumed the distribution of tiny extraterrestrial objects is evenly distributed around the world, extrapolating from the relatively small sample area to the entire area of the Earth.