Jon Larsen - In Search of Stardust: Amazing Micrometeorites and Their Terrestrial Imposters

SEM images shown have a catalog number with a hyphen. These are from the South Pole Water Well (SPWW), the Antarctic reference collection of micrometeorites, SEM images by Emily Schaller, published with kind permission from Susan Taylor (US Army Cold Regions Research, CRR).

Micrometeorites belong to the oldest matter there is: mineral remnants from before the planets were formed. They may even contain stardust older than the sun, particles which have traveled farther than anything else on Earth. We are just beginning to explore these alien stones, yet they are everywhere around us.

After an incident in 2009 when a micrometeorite literally landed on my table, I wanted to find out more about them, and became intrigued by the contradiction between the global influx rate (see in this book, human tools and activities create spherules not unlike micrometeorites.

To pick out one extraterrestrial particle among billions of others requires knowledge both about what to look for and what to disregard, and initially I was in the dark. The published images of micrometeorites from the Antarctic were mainly black/white SEM sections (shown ), which are poor representations of what micrometeorites look like. And with regard to the confusing contaminants there was a plentitude of speculation, but very little empirical data. There has been research in this field earlier, from NASAs comparative analysis of cosmic and industrial spherules in the 1960s to contemporary studies of road dust in India and Hungary, but these have been fragmentary, and concluded that separation of micrometeorites in populated areas is not possible. On the other hand there have been several physics-at-home experiments searching for micrometeorites at downspouts from roofs gutters, but none of these have yet resulted in verification of extraterrestrial particles.

In the spring of 2010 I started my systematic research on dust samples from populated areas. I initially looked at skywards-facing hard surfaces where particles could accumulate over time, like roads, roofs, parking lots, and industrial areas, and then graduated to look in other cities, countries, mountains, beach sand, desertseverywhere. Now, six years later, I can look back upon nearly 1,000 field searches in nearly 50 countries, all continents represented. The samples were examined in a Zeiss binocular microscope, and interesting particles were picked out, photographed with a USB microscope, and stored in the archive. I established a photo database (now containing photos of more than 40,000 individual objects), kept an illustrated journal, and tried to look for patterns (factor analysis) while I put my complete trust in pure empiricism. The Facebook page Project Stardust was established to share the results.

To begin with the different types of anthropogenic and naturally occurring terrestrial spherules seemed infinite and chaotic, but with time I gradually started to recognise the most common ones. There are surprisingly small variations in the types of spherules found in comparable environments around the globe, and the 25 types presented in this book represent the most of all the spherules found anywhere. The micrometeorites are rare and evenly distributed, so an abundance of one type of particles found locally is one of the indications of terrestrial origin.

The breakthrough in my research came February 4, 2015, when Matthew Genge verified the first micrometeorite, a barred olivine beauty with dendritic magnetite crystals sprinkled all over the surface. The stone was only 0.27 mm, and was found at Brevik in Frogn, Akershus, Norway.

At last I knew what to look for, started immediately to search for similar stones, and found them. Within the first season I had a collection of more than 500 pristine micrometeorites, all the most common types from the classification represented.