Searching for stardust: How to find micrometeorites in your gutters

It was a warm summer morning in the countryside near Oslo, so John Larsen decided to have breakfast outdoors. He carefully wiped down the white plastic table on the patio and went inside to get his food. Then, when he sat down to eat, he noticed a small black dot on the table. “It was shining in the sunlight,” he says. “I thought, wow, what is this?”

That was in 2009. Ten years later, Larsen has managed to do what many thought was impossible. He showed that you can find your own micrometeorites – tiny specks of extraterrestrial dust that have been floating around since the birth of the solar system billions of years ago – just by exploring ordinary urban spaces. His collection currently consists of over 3000 of his specimens and boasts a large fan base of urban space dust hunters.

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I had heard a little about Larsen’s work and got the impression that following in his footsteps wouldn’t be all that difficult. Apparently all I needed was dirt from an intact roof and a microscope. Can you really find your own Stardust? I almost found out.

A meteorite is a mass of debris left over from the early days of the solar system that survived its passage through the atmosphere and crashed into the ground. These are almost all fragments of asteroids orbiting between Mars and Jupiter, and they provide a complete record of conditions in the early solar system, information we have used to understand how planets formed. contained.

Micrometeorites are obviously much smaller. To qualify, it must be less than 1 millimeter. But they are even more mysterious. “If you crush a meteorite, you don’t get micrometeorites,” says Cécile Angrin of the University of Paris-Saclay in France. Micrometeorites, unlike their larger cousins, appear to have not been heated at all since forming during the solar system’s birth, and represent the solar system’s most primitive material.

We don’t know for sure whether they came from the farthest reaches of the asteroid belt or from comets. But we do know that while most regular meteorites are completely dry, the majority of micrometeorites contain water and carbon-containing compounds, the building blocks of life. One hypothesis is that these particles, disseminated slowly and steadily, helped fill Earth’s oceans. “For me, it’s strange to be able to look at something so small under a microscope and use it to understand its connections to the entire solar system,” Englund said.

Finding space rocks often requires expeditions into the desert, where meteorites stand out against the background of the plains. Even there, it’s not easy. Large meteorites are rare. However, smaller meteorites are more common, and when you get down to the micrometeorite scale, you end up with a steady stream of rain. According to estimates, about 100 tons of these particles fall to Earth every day, which corresponds to approximately 2 particles of dust per square kilometer per second. In other words, there is a good chance that someone could have landed on any roof.

Searching for them has always been considered a futile task, mainly because you have to walk through vast amounts of earth dust. It’s like finding a needle in a whole barn in a haystack. Matthew Genge of Imperial College London studies micrometeorites recovered from remote areas such as Antarctica, where there is almost no Earth’s dust. He says enthusiasts regularly send him letters claiming to have discovered objects, but rarely do they actually find them.

“It is estimated that about 100 tons of micrometeorites fall to Earth every day.”

Larsen wasn’t the most obvious candidate to succeed while so many others have failed. Although he had an amateur interest in geology all his life, he made a living as one of Norway’s most famous jazz guitarists (though he recently retired, he played in the band he founded in 1979, Hot Club).・De Norvege is still active). . But he describes himself as obsessive, and once a speck that suddenly appeared on his breakfast table intrigued him, there was no turning back. “Every day he would get two truckloads of dust coming in, and I started thinking he couldn’t find any of it,” he says. “That’s so strange.”

dust book

Larsen started a strange habit while touring with his band. At each new city, he collected dust samples and examined them under a microscope. The problem was, he had no idea what he was looking for. Some published photos of micrometeorites are grainy black and white image of a scientific paper. These suggested that he should look for black spheres about 1 millimeter wide, but the debris he collected contained a lot of debris that fit that description, and all of them came from space. That wasn’t necessarily the case.

Larsen reasoned that different types of terrestrial dust, such as those from industrial processes or the environment, should exist in different amounts depending on location. For example, industrial cities may have more dust generated by welding. But cosmic dust should appear in equal amounts everywhere. So he began a systematic investigation and over a period of seven years identified his 75 most common types of terrestrial dust.

Anything that doesn’t fit into these categories is probably cosmic dust. He started sending this photo to Genge in London. “In the first place, I just wanted him gone,” Genge says. But Larsen persisted. The particles he discovered were typically round, black, and had a kind of shiny, deeply grooved shell. This was to be expected, as micrometeorite particles dissolve as they pass through the atmosphere, and their surfaces are often shaped into small undulations by the blowing air.

Eventually, Genge was persuaded to analyze the chemical composition of the dust, and in 2015 the two announced that they had indeed discovered the first urban micrometeorite.

Now it’s my turn to find this amazing space dust. I borrowed a ladder and climbed up to the rain gutter on the roof. I then used a garden trowel to scrape out the contents and placed them in a plastic sandwich bag. The weather was nice so there was mostly just dry dusty stuff and clumps of moss that the magpies had ripped off the tiles. It wasn’t the most glamorous 15 minutes of my life, but somewhere beneath the moss, feathers, and dirt, there just might be a little cosmic prize.

On the trail of stardust, Larsen’s Guidebook for Stardust Hunters, explains that the next step is to separate the ordinary dust from the cosmic stuff. First, I transferred the bag of roofing mud to a plastic bowl, added water and detergent, and stirred it. I took out what floated and once the solids settled to the bottom, I decanted the brown water. After repeating this a few times, I was left with a nice little stone plate.

Pass these pieces through an old tea strainer to remove any large chunks. Finally, I grabbed a strong magnet I bought online, covered it with a plastic bag, stirred it in the dust, and transferred the magnetic material to a white bowl. This is a crude tactic since not all micrometeorites are magnetic, but it greatly reduces the amount of dust you’re dealing with.

The next step is to find each speck of dust. I bought a cheap USB microscope and started looking. There is a fascinating world out there. At 60x magnification, some spots look like colorful popcorn pieces or dark spiky stars. Others are translucent gemstones of various colors. Red, blue, and delicate green.

I knew to look for round black beads. But I’m also on the same level as you. At this stage I was almost heartbroken. It took at least seven hours to wade through the dust. Sometimes I would find something that looked promising, only to lose it again. Several nights, her wife had to explain that she had more important things to do right now, like reading a bedtime story to her children.

In the end, I found and photographed seven works that looked promising. The only sure way to know if you’ve found a micrometeorite is to do a chemical analysis of it, but Larsen is such an expert that you can usually tell just by looking. I sent him a photo and he laughed good-naturedly. He saw no convincing signs that these spots came from outer space.

I thought meteorite hunting was easy and inexpensive. In total the price of my magnet, USB microscope and other parts was less than £30 for him, but Mr Larsen said the size of the lab sieve he used to separate particles between 0.2 and 0.4 millimetres. I said it would be a good idea to get some. This is where most of the micrometeorites are hidden, and using the sieve will greatly reduce the time it takes to find them, he says. A binocular microscope is also required to observe the surface texture of the particles. This is the best way to identify particles of cosmic origin.

I haven’t found my space dust yet, but I tracked down the man who did. We contacted Jens Metsurat, a student at Germany’s Clausthal University of Technology. He’s been interested in hunting micrometeorites since he was a child, but his pursuit kicked into gear after discovering Larsen’s work. Metsulato said he found eight particles in three months using Larsen’s method, one of which was more than half a millimeter long, making it one of the largest micrometeorites. Obviously, it’s possible.

Larsen wrote his magnum opus, a 300-page book, star hunter. He is also continuing his search. What’s exciting for him now, he says, is that with the sheer volume of discoveries, we’re starting to find rare types of micrometeorites. Recently, he discovered a material rich in the rare element scandium, as well as a material containing the same carbon-based molecules that form the basis of all living things.

“It took at least seven hours to sift through the bowl of dust. It almost broke my heart.”

You might be wondering what happened to the speck that started it all on Larsen’s breakfast table. Well, not knowing the best way to store microscopic particles, he puts them in a matchbox and loses them. I take some kind of comfort from that story. This goes to show that even the best stardust hunters can have humble beginnings.