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  • [♪ INTRO]

  • When we think of space rocks falling to Earth,

  • we usually think of meteors blazing dramatically across the sky or dinosaurs-killing asteroids.

  • But most of the meteorites that land on this planet are pretty teeny, like,

  • smaller than a grain of sand.

  • They're called micrometeorites.

  • And astronomers estimate 60 tons of them or more fall to Earth every day.

  • That means they're theoretically everywhere,

  • so you could have a little meteorite for yourself if you wanted.

  • Fair warning, though: it'll take a bit of work to find it.

  • Micrometeorites begin as bits of comets and asteroids.

  • When asteroids collide, loose pebbles and dust are knocked off.

  • And comets are composed of rocky debris and dust encased in ice, so as they approach the sun,

  • the water often sublimates, releasing the dust it once held.

  • If this space dust survives its trip through Earth's atmosphere, it lands on our planet,

  • and the tiny particles are called micrometeorites.

  • They range in size, but the average is around 200 micrometers, which is teeny,

  • wider than a strand of hair, but only barely.

  • Basically, you need a microscope to see them properly.

  • But they're worth seeing, as many of them are beautiful.

  • They're often metallic or glasslike, though they can be all sorts of shapes, colors, and textures.

  • Among the most distinctive are cosmic spherules,

  • which are almost perfectly round because they melt and then reform upon entry into the atmosphere.

  • Setting aside the gee-whiz factor,

  • micrometeorites are also cool because they give us a better sampling of the galaxy

  • and can help us learn different things about it than their larger cousins.

  • For one, there's just more of them to look at.

  • But they also have a different travel experience out there in space than larger rocks do,

  • which means that they can sometimes be a more representative sample of

  • where they originally came from.

  • And if that's not cool enough for you?

  • One astronomer hypothesized that they could help account for the missing mass in the universe

  • that's usually attributed to dark matter.

  • Okay, so now you know how truly awesome these little space rocks are, and you want one for yourself.

  • Well, in theory, they're not all that difficult to find.

  • Really, all you need is a strong magnet, some Ziploc bags, a microscope,

  • and the goop in your rain gutters.

  • The idea is that your gutters collect all the stuff that lands on your roof

  • and gather it into one convenient location.

  • So you'll want to collect that goop, and pick the leaves and stuff out.

  • Then, you can use a strong magnet to find any tiny, magnetic bits.

  • Not all space dust is magnetic, but metallic micrometeorites containing nickel and iron

  • are the only ones you'll have a chance at distinguishing from bits of Earth dust.

  • And you'll want to place a Ziploc bag over the magnet first,

  • so that you can get the stuff that sticks to it off again.

  • Once you've collected your magnetic dust, you'll want to use a microscope to look

  • for dark, metallic or glassy semi-spherical objects with weird patterning to them.

  • Those should be your teeny space rocks.

  • Though, there's a bit of a catch.

  • See, there are other things that fit that description, too.

  • In particular, welding debris, fly ash from furnaces,

  • and industrial dust from coal power plants can masquerade as micrometeorites.

  • And it can sometimes be tough to separate those from actual space dust

  • without expensive scientific equipment.

  • That's why most researchers look for them in remote places,

  • to avoid confusing space dust with Earth dust.

  • In fact, until recently, they didn't really think it was possible to find urban micrometeorites.

  • But then, in 2017, a scientist leading an effort called Project Stardust

  • published a paper identifying over 500 of them from rooftops in Oslo, the capital of Norway.

  • It was the culmination of years of work.

  • And he and a team of volunteers had to comb through 300 kilograms of roof goop to find them.

  • From the 500 micrometeorites they identified,

  • the researchers selected 48 particularly likely suspects to study under an electron microscope.

  • That closer look allowed them to classify all of them as cosmic spherules.

  • They also performed chemical analyses to confirm that they actually included the kinds of iron, silicate, and minerals

  • you'd expect in something that's from space.

  • And all of them did, demonstrating that you really can find micrometeorites pretty much anywhere

  • if you look hard enough.

  • One thing that is rather cool is that these micrometeorites tended to be much younger

  • than the ones researchers usually find in Antarctica and other remote places,

  • probably because, well, gutters get cleaned fairly regularly.

  • They were likely only about six to 50 years old when they were recovered.

  • This means that they can tell us things about space that we might not learn from the micrometeorites

  • we find elsewhere,

  • including stuff about what's happened out there more recently.

  • For instance, the researchers found that different types of micrometeorites

  • tended to occur in different amounts in the urban sample than in older samples,

  • which implies that they arrived at Earth at different velocities.

  • The researchers suggest this could imply changes in the orbits of the clouds of dust

  • that Earth encounters over time.

  • Based on their findings, the team estimated that roughly

  • two micrometeorites fall on every square meter of roof each year,

  • though, they only recovered one thousandth of that in their search.

  • So, yeah, there are probably micrometeorites on your roof, or will be somewhat soon.

  • And with some simple tools, you can go space rock hunting right at home!

  • It's definitely possible you'll find something.

  • It just might take a while.

  • Have you ever tried to find a micrometeorite?

  • If so, let us know how it went in the comments.

  • And if you liked learning about these teeny little meteorites,

  • you might like our episode on three weird kinds of meteorites.

  • So maybe watch that one next.

  • And thanks for watching SciShow Space!

  • [♪ OUTRO]

[♪ INTRO]

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