BY: PHILIPPE DE JOCAS
Ever wonder why your meticulously clean furniture quickly develops a film of dust when left alone? Sometimes it seems as though you’ve only just put down the feather duster before you’re forced to take up arms once more. Dust consists of a varied “tossed salad” of ingredients – bits of dead skin, mite poop, and other unpalatable substances. What a lot of frustrated housekeepers don’t realize is that a good chunk of that dust comes from (insert a theremin cue here) outer space.
Neat-freaks of the future won’t be happy to learn that space is dusty. There are different kinds of dust: stardust, for instance, is a mishmash of leftover refractory material left over from the birth of a star, while ancient intergalactic dust lingers in the void between galaxies, remnants of galactic formations. Some dust samples coalesce into huge incandescent nebulae, but the vast majority simply drifts through space for millions of years. A small percentage of that gigantic quantity of dust gets dragged into the gravity wells of planetary bodies – including Earth. Clumps of dust melt in the atmosphere as they plummet to Earth at more than 12 kilometres a second, then waft down to the surface where they accumulate. Cosmologists estimate that every year, the Earth attracts more than 40,000 tons of dust.
Scientists have long researched the different kinds of dust that make up great swathes of the cosmos, and although there’s a lot of dust on Earth, the real problem is picking out the good space dust from the morasses of unremarkable Earthbound dust. Although 40,000 tons of space dust sounds like a lot, it’s a comparatively small amount when weighed against good old-fashioned Earth dust. When scientists do need to go hunting for some space dust, they tend to search in relatively sterile environments, such as the Antarctic ice sheets or deep underwater, where Earthbound dust couldn’t accumulate.
For a long time, there was no way to reliably locate space dust samples in greasy, grimy, cities. Recently, however, the Imperial College of London, England, has started searching for dust samples in Paris and Berlin using some remarkable new techniques involving magnets. Most space dust contains metallic residue in its structure. Using special magnets, researchers sifted through gutter runoff, street sweepings, and other dusty environments in search of these unique dust nodules. Their search yielded more than 500 grains of dust – an unprecedented amount of space dust recovered in an urban area.
You might be asking yourself why on earth scientists would be risking life, limb, and hygiene in order to get their hands on a few measly crumbs of drifting space debris. The answer: cosmic dust provides a great way to track the changing cosmology of the solar system. Over millions of years, the planetary paths have changed due to orbital fluctuations, altering the gravity exerted by each planet on the matter around it. Spectrographic analyses on dust particles allow scientists to determine when dust fell to Earth, allowing scientists to cross-reference the dust’s position with other recovered samples of cosmic dust. From there, we can learn how our Earth has changed its orbital path and eccentricity over the centuries.
The more dust we gather and analyze – and a lot of this dust has stuck around on Earth for centuries – the better we can understand the early days of the solar system and the unique circumstances surrounding life on Earth. So next time you whip out the Swiffer, take a moment to remember the epic voyage of the dust on your end table.