Microscopic Meteorites Are All Around Us

Various types of micrometeorites (credit: © Jon Larsen)

In 1970, a machine was rigged onto a high-altitude atmospheric balloon and sent 21.7 miles (35 km) into the sky over Texas. The machine, lovingly named the Vacuum Monster after a creature in The Beatles' Yellow Submarine movie, collected microscopic particles as small as two micrometers (microns) in diameter. Some of which were determined to be extraterrestrial, marking this as the first time "space dust", or more precisely, micrometeorites, were collected at altitude.

Micrometeorites are a niche area of study within astrogeology (the study of the geology of extraterrestrial bodies), but has recently been expanding as it is now more accessible for researchers. On a large scale, international space agencies have devoted funding for missions to collect material directly from asteroids and comets, such as the ongoing Hayabusa 2 mission to the asteroid Ryugu, which has very recently completed its sampling goals and is to return to Earth in December 2020. On Earth, the study of micrometeorites has been largely regulated to remote areas such as Antarctica or in deep sea sediments, which were the first source of reported micrometeorites during a scientific expedition of the HMS Challenger from 1873-1876. Recently however, there have been several discoveries of micrometeorites in more attainable places, such as a rooftop in Brooklyn, New York, thanks to an amateur geologist.

Schematic of the Vacuum Monster that collected the first confirmed micrometeorite in 1970¹.

In 2009, Jon Larsen, a musician from Norway, took an interest in micrometeorites when one such object "literally landed on [his] porch table"². Wanting to know more about these rocks, Jon then established Project Stardust to search for micrometeorites and did so in an unorthodox locality - urban environments. He reasoned that broad, flat rooftops could be ideal for space-borne material to be deposited. After six years of hard work, he was able to verify "the world's first urban micrometeorite" and after finding several more, he wrote two books: In Search of Stardust: Amazing Micrometeorites and Their Terrestrial Imposters (2017, Voyageur Press) and On the Trail of Stardust - The Guide to Finding Micrometeorites: Tools, Techniques, and Identification (2019, Voyageur Press). 

Like typical meteorites, micrometeorites are also rare, and most of the material he has found is from other natural sources, such as volcanic dust, or is artificial, such as glass and iron from industrial sources. For his books, Jon photographed many, many wonderful examples of these artificial and natural objects, in addition to micrometeorites. I bought a copy of his second book, On the Trail of Stardust, immediately after watching this video below where Jon Larsen is interviewed by Cory Zapatka from The Verge, who goes on the hunt for micrometeorites atop a roof in Brooklyn, New York:

A follow-up to that video was recently posted by The Verge to discuss the results from the previous video:

Not all meteorites are the same, some are predominately made of iron and nickel, others may include olivine crystals, and others they may be cobbled together bits of existing rocks. So, not all micrometeorites are the same (see image at top) and are surprisingly diverse. Jon's second book details his methods of collecting and analyzing material for micrometeorites so others can get involved. Undoubtedly, Jon's research has created a new hobby for amateur geologists and will have profound positive implications for those who study meteorites and astrogeology. Check out the videos above and for more photos, visit the Project Stardust page on Facebook.


Sources:
¹ Brownlee, D.E, Hodge, P.W., and Bucher, W., 1973, The physical nature of interplanetary dust as inferred by particles collected at 35 km in Evolutionary and Physical Properties of Meteoroids, Proceedings of IAU Colloq. 13, held in Albany, NY, 14-17 June 1971, Hemenway, C.L., Millman, P.M., and Cook. A.F. (eds.): NASA SP 319, p. 291-295.

² Larsen, J., 2019, On the Trail of Stardust - The Guide to Finding Micrometeorites: Tools, Techniques, and Identification, Voyageur Press: Beverly, Massachusetts, 144 p.