Whenever I wipe the dust off my coffee table or catch a glimpse of dust motifs floating in the sunlight, my space-worthy mind always wonders if this cosmic dust is something.
It could be easy. But the amount of space dust that lands on our planet each year might surprise you.
Scientists have long known that extraterrestrial material is deposited on Earth each year, mostly in the form of tiny particles, mostly from comets and asteroids. These grains of dust, less than a millimeter in size, can make it through our atmosphere unscathed. However, the exact amount has never been calculated due to the difficulty of collecting and monitoring this dust. The biggest problem is that the earth itself and the atmosphere are dusty places. So when you collect dust, how do you differentiate between earth dust and space dust?
For the past 20 years, a group of scientists has been collecting dust from the least dusty place on earth: the plains of Central Antarctica, which are always covered in snow and ice.
Dome C Antarctica Station. Photo credit: Stephen Hudson, public domain, via Wikimedia Commons.
An international collaboration of researchers from France, the USA and the UK carried out six expeditions over two decades to the Franco-Italian Concordia station called Dome C, which is 1,100 kilometers from the coast of Antarctica. The area of Dome C is considered ideal for the study of micrometeorites due to the almost no formation of earth dust and the low rate of snow accumulation.
With the help of a calculated system for taking snow samples in 2-meter-deep trenches, the researchers collected extraterrestrial particles with a size of 30 to 200 micrometers. They have been able to collect enough samples over the years to measure an annual flux equal to the mass accumulated on Earth per square meter per year.
The team reports that the total annual flux of micrometeorites is 5,200 tons per year when their results are applied to the entire planet.
Collecting micrometeorites in the Central Antarctic regions, 2002 in Dome C. Snow samples. Photo credits and copyright: Jean Duprat / Cécile Engrand / CNRS Photo Library
“This is the main source of extraterrestrial matter on our planet, far ahead of larger objects like meteorites, for which the flow is less than ten tons per year,” said Jean Duprat, lead researcher from the French National Center for Scientific Research (CNRS).
To determine how much cosmic dust falls into my environment per year, a quick calculation of the back of the envelope gives about 9 grams per square kilometer, or 0.85 ounces per square mile.
In other words, we don’t have to worry about a Pompeii-type event covering us in cosmic dust every year.
The team’s paper also explains how small particles of space dust get through our atmosphere without being burned:
The degree of heating of the particles during their atmospheric entry depends on several factors including the initial mass of the particles, their entry angle and their velocity. The removed metal vapors oxidize and the resulting metal oxides, hydroxides and carbonates condense into nanometer-sized particles known as meteor smoke (Plane et al., 2015). These particles are transported through the general atmospheric circulation until they finally settle on the surface, where their flow can be assessed by elementary or isotope measurements (Gabrielli et al. (2004)).
The research team compared the flow of micrometeorites with theoretical predictions and confirmed that most of the micrometeorites likely came from comets (80%) and the rest from asteroids.
The researchers say their study provides valuable information to better understand the role of interplanetary dust particles in supplying the young earth with water and carbonaceous molecules.
The study will be available on April 15 in the journal Earth & Planetary Science Letters and is available here.
Further reading: CNRS press release
Caption: Electron microscope image of a Concordia micrometeorite extracted from Antarctic snow at Dome C. Photo credit: Cécile Engrand / Jean Duprat
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