Every second, billions of teeny-tiny missiles strike Earth. They come from outer space. But it’s not an alien attack. These speeding objects are actually bits of space dust. They come in all sizes. Some contain only a few molecules. Others are similar in size to the specks under your bed that glom together into dust bunnies. And the biggies? They can be the size of sand grains.
Some of these specks formed when asteroids slammed into planets, moons or other space rocks. Others are debris left behind by comets streaking around the sun. And a few have traveled in from way outside our solar system. What all of these motes have in common is speed. They fly at up to 72 kilometers per second (45 miles per second). That’s 50 times faster than a speeding bullet!
Such super-speedy dust grains can damage equipment orbiting in space. In fact, they can punch right through metal or glass. So why don’t these falling microrocks harm our roofs or roads — or even our bodies? Thank a gigantic shield that protects our planet. The air all around us may seem like nothing. To a dust grain zooming through the near-emptiness of space, however, that air might as well be a solid wall.
After smacking into the atmosphere, space dust slows down. Some bits vaporize, giving off a lot of heat and light. Specks the size of a grain of sand or larger can shine brightly enough to see. These are known as meteors, or shooting stars. (Larger space rocks can become shooting stars, too.) Some space dust vaporizes completely. But other specks melt, solidify again and then fall gently to the ground. There, they tend to mingle with all of the other dust from various sources.
Throughout the journey of a speck of space dust, scientists are watching and learning. Researchers study how space dust damages satellites. They work out what happens when bits of dust collide with particles in Earth’s atmosphere. And on the ground, they’re sifting through gutters in search of micrometeorites — bits of space dust that have survived the long journey to Earth.
One moment, the satellite Copernicus Sentinel 1A was minding its own business, taking pictures of Earth’s surface. The next, something smacked into one of the solar panels that provide power to the craft. The impact made a dent wider than a basketball. The culprit was a speck of space dust about as big as a grain of sand. Luckily, the damage wasn’t too bad. Lots of the satellite’s other solar panels still work.
A speck of space dust no bigger than a sand grain hit this satellite in 2016. The picture on the left shows the solar panel before the impact. The picture on the right shows the dent (red arrow) afterward.ESA
How does something as tiny as a sand grain make such a large dent? The key is speed. “These things are going insanely fast,” says Sigrid Close. She is an engineer who studies spacecraft design at Stanford University in Palo Alto, Calif. That high speed gives larger grains enough power to puncture a spacecraft.
But large grains are fairly rare. Most space dust particles are microscopic. The dents or tiny holes they make are nothing to worry about. They might cause another type of damage, though. Sometimes, electrical systems on spacecraft fail and no one can figure out why. Close thinks teeny specks of dust might be to blame for some of these failures.
When a speck slams into a spacecraft, it explodes. The explosion “looks like a tiny little nuclear detonation,” says Close. If the impact happens at a high enough speed, it creates a burst of radiation, known as an electromagnetic pulse (EMP). It will send a jolt of electricity through any nearby electronics. This may cause a glitch or shut them down.
In the lab, Sigrid Close slammed fast-moving specks of dust into spacecraft materials. The impacts caused brief, bright flashes of radiation like this one. Any electronics close to this type of flash could permanently stop working. S. Close
In experiments on Earth, Close pelted spacecraft materials with fast-moving particles. Then she measured the explosions. The EMPs were strong enough to mess up electronics, she confirmed.
These EMPs likely would not affect any equipment deep inside a spacecraft or station. But they could mess with electronics on the outside of a spacecraft, such as the antennae that transmit data. If an astronaut were out on a spacewalk and a dust speck hit the spacecraft nearby, an EMP could potentially knock out communications, says Close. Her work aims to help engineers figure out better ways to shield electrical equipment from these micro-impacts.
Dust to dust
Earthbound specks that don’t slam into satellites or other objects will have to survive a new obstacle: air. The atmosphere is made of gas molecules and bits of floating Earth dust. That air thins the higher you rise.
In the very upper reaches, 150 kilometers (more than 93 miles) off the ground, an interesting thing can happen. Space dust can “[scrape] off bits of the atmosphere,” explains Arjun Berera. He is a theoretical physicist at the University of Edinburgh in Scotland. Specks of space dust can send Earth’s native dust careening off into space.
It’s like what happens when one ball strikes another during a game of mini golf. The first ball stops or slows down as the smacked one speeds away. In the upper atmosphere, speeding space dust gives drifting gas molecules or dust specks a huge kick. They can get moving fast enough to escape the pull of Earth’s gravity, Berera’s calculations show. And in the thin air, this gives them a good chance of flying off into outer space without crashing into anything else on the way.
Such particles may now end up traveling to other planets. If they are moving fast enough, they might even sail on to other solar systems. That means Earth might be able to exchange parts of its sky with those of other worlds.
Could the planets exchange more than just gas and dust? Could microscopic life forms get caught up in the action? Berera thinks it’s possible. So space dust, he says, might help spread Earth’s life through the universe. It’s not a given, he adds — but a big “maybe.” And here’s why.
A microbe would have to be floating very high in the air for a space speck to kick it out of the atmosphere. Microscopic life forms do live in the sky. But people have only found them up to about 15 kilometers (9 miles) above Earth’s surface. That’s just a tenth the altitude they’d need to get catapulted into space by a space-dust encounter.
It’s possible that microscopic life exists at this height. To date, however, no one has seen that. In the far reaches of the upper atmosphere, everything is spread out very thinly. Finding any life up there “would be like looking for a needle in a pack of hay,” says Kostas Konstantinidis. At the Georgia Institute of Technology in Atlanta, he studies the life forms in Earth’s atmosphere.
He was not involved in Berera’s research. He does, however, think it makes sense that some life forms would make it to the upper atmosphere. They would just be very rare.
If high-flying microbes exist, they’d have to survive a rapid collision with a speck of space dust. Then they’d need to hunker down for a long journey through outer space. Finally, they would have to land somewhere with water and other necessities for staying alive.
This all seems highly unlikely. But some microscopic life is incredibly tough. Certain microbes can shut down their metabolism . That means they basically turn off their bodies. They can spend thousands of years in that suspended animation. Only when conditions improved would they can start growing again, he says.
The thought that space dust might send microscopic life rocketing between the planets is “a good, crazy idea,” Konstantinidis says. It will take many more experiments, however, to confirm whether this could happen.
Jon Larsen (right) gathers dust from a rooftop with meteorite expert Morten Bilet. They’ll sort through the dust to look for tiny rocks from space.Morten Bilet
Finding treasure in the gutters
Jon Larsen knows crazy ideas. He is a jazz musician in Oslo, Norway, who has always enjoyed rock hunting. One June morning in 2009, he was eating breakfast outside at his vacation cottage. “Suddenly this small dot appeared on my table,” he says. “I put it on my fingertip.” It was a very tiny, round rock. It seemed to have fallen straight out of the sky.
Larsen’s rock hunting suddenly took a crazy turn. He decided to search for micrometeorites — space dust that has made it all the way to the ground. He learned that such micro-rocks fall to Earth all the time. But no one thought it was possible to find them in cities. Most micrometeorites are black, shiny stones, spherical in shape. Dust from power drills, engines, factories and other human activities can look similar.
Michael E. Zolensky (left) spent 25 years working on the NASA Stardust mission, which retrieved space dust from a comet. When Jon Larsen (second from right) visited his team at the Johnson Space Center in Houston, Texas, he found five micrometeorites on the roof! Larsen joked that he could have saved the team billions of dollars. Also in the photo: James Martinez (second from left) and photographer Jan Braly Kihle (far right). Jan Braly Kihle
But Larsen didn’t let this fact stop him. He began collecting dust from roadsides and scooping it from rooftops. “It’s a very dirty job,” he says. He looked at the dust under a microscope and began sorting it. He learned the difference between specks of pavement and grains from fireworks. He looked at dust from a welding shop and a steam locomotive. He learned to recognize dust that definitely wasn’t from space.
A breakthrough came in 2015. That’s when he found his first micrometeorite. He was at his cottage again. “I found one in the rain gutter,” he says. Matthew Genge, a meteorite expert in England at Imperial College London looked at a picture of his prized speck. It looked promising, so he invited Larsen to his lab. There, Genge ran that grain and several dozen others through tests. At the end, he concluded that Larsen had found 50 micrometeorites.
Now, Larson has become a guest researcher at the University of Oslo. He’s found thousands of micrometeorites and written two books about the process. Anyone can do it, he says.
The first step is to gather dust. Rooftops are the best place to look, Larsen says. He rinses the dust and then uses a screen to filter out particles more than 300 micrometers wide — roughly four times the width of a human hair. Then he dries the dust, puts a plastic bag over a magnet and passes the magnet over the dust. Most micrometeorites are magnetic. So he carefully pulls the bag off the magnet to collect any dust that has stuck. These grains are what he looks at under a microscope.
Even after all these steps, Larsen might look at 10,000 grains to find just one from space. “They are rare, lonely, small rocks,” he says. “But they are everywhere. You will find them on absolutely every roof.”
Larsen takes beautiful photographs of the micrometeorites he finds. He’s even displayed their images in an art gallery. But his work has had an impact on science, too. Researchers study micrometeorites to learn about the solar system. Each speck is like a time capsule from a long-ago collision or other cosmic event. Larsen has made it easier than ever to locate these rare bits of space dust. In his spare time between gigs as a jazz artist, “He ended up making a discovery that professional scientists missed,” Genge says.
Grains of space dust may be small, but they can have a huge impact. Sometimes it’s a headlong crash into a satellite or a particle careening through Earth’s atmosphere. At other times, its impact can be seen on science itself. When people find these minuscule missiles from space, they can give science a glimpse into the history of our solar system and the universe beyond.
Jon Larsen found all of these micrometeorites on rooftops. They were mixed in with Earth dust.JAN BRALY KIHLE/J. LARSEN
Jon Larsen found all of these micrometeorites on rooftops. They were mixed in with Earth dust.JAN BRALY KIHLE/J. LARSEN
alien A non-native organism. (in astronomy) Life on or from a distant world.
asteroid A rocky object in orbit around the sun. Most asteroids orbit in a region that falls between the orbits of Mars and Jupiter. Astronomers refer to this region as the asteroid belt.
astronaut Someone trained to travel into space for research and exploration.
atmosphere The envelope of gases surrounding Earth or another planet.
comet A celestial object consisting of a nucleus of ice and dust. When a comet passes near the sun, gas and dust vaporize off the comet’s surface, creating its trailing “tail.”
cosmic An adjective that refers to the cosmos — the universe and everything within it.
debris Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.
electricity A flow of charge, usually from the movement of negatively charged particles, called electrons.
electromagnetic pulse (or EMP) A rain of high-energy electrons emitted by an explosion. This radiation travels speedily in a line of sight direction out from its source. Unlike radioactive fallout, this radiation won’t directly harm living things. It will, however, catastrophically fry all electronics and modern electrical systems by inducing staggeringly large and rapid current or voltage surges. EMPs have been discussed as a potential type of non-lethal weaponry. A nuclear detonation at high altitude could cripple electronics throughout the areas below hit by its EMP. It would leave people without electric appliances, computers, vehicles or phones.
electronics Devices that are powered by electricity but whose properties are controlled by the semiconductors or other circuitry that channel or gate the movement of electric charges.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
filter (in chemistry and environmental science) A device or system that allows some materials to pass through but not others, based on their size or some other feature.
gravity The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.
magnet A material that usually contains iron and whose atoms are arranged so they attract certain metals.
metabolism (adj. metabolic) The set of life-sustaining chemical reactions that take place inside cells and bigger structures, such as organs. These reactions enable organisms to grow, reproduce, move and otherwise respond to their environments.
metal Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure).
meteor A lump of rock or metal from space that hits the atmosphere of Earth. In space it is known as a meteoroid. When you see it in the sky it is a meteor. And when it hits the ground it is called a meteorite.
meteorite A lump of rock or metal from space that passes through Earth’s atmosphere and collides with the ground.
microbe Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.
microscope (adj. microscopic) An instrument used to view objects, like bacteria, or the single cells of plants or animals, that are too small to be visible to the unaided eye.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O 2 ), but water is made of two hydrogen atoms and one oxygen atom (H 2 O).
native Associated with a particular location; native plants and animals have been found in a particular location since recorded history began. These species also tend to have developed within a region, occurring there naturally (not because they were planted or moved there by people). Most are particularly well adapted to their environment.
particle A minute amount of something.
physicist A scientist who studies the nature and properties of matter and energy.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood.
radiation (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
sentinel A guard or something that watches over others, or that effectively offers some warning of a potential problem. (in ecology) Species that scientists monitor to get information about the environment in which those organisms live. These species might be more sensitive to some environmental hazards, and so can indicate to researchers when those hazards are reaching dangerous levels.
solar system The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
spherical Adjective for something that is round (as a sphere).
theoretical An adjective for an analysis or assessment of something that based on pre-existing knowledge of how things behave. It is not based on experimental trials. Theoretical research tends to use math — usually performed by computers — to predict how or what will occur for some specified series of conditions. Experimental testing or observations of natural systems will then be needed to confirm what had been predicted.
transmit (n. transmission) To send or pass along.
universe The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
vaporize To convert from a liquid to a gas (or vapor) through the application of heat.