Don't Clean Your Room…
by Meg Moss, art by Mike Gordon
There's space dust under your bed. But don't bother calling NASA; they're already on the case.
Space, it turns out, is a very dirty place. It's filled with particles and debris from billions of years of exploding stars, colliding asteroids, and comet tails. Space dust sometimes obscures our view into the universe, and 100 tons a day—nearly 40,000 tons a year—fall to Earth. You can be sure some of it is under your bed right now. Mars and the Moon, as well, are covered with dust and dirt we are eager to know more about.
Clues in the Dust
Why is space dust and dirt so interesting? Inside every grain is a record of the universe. Astronomers believe that our solar system, and planets and stars all over the universe, formed from huge clouds of dust and gases that are the remains of dying stars. Collecting and analyzing space dust may help us understand what happened 5 billion years ago when Earth was born. We may also find clues about what's happening right now in the far corners of the universe.
Powerful telescopes give us a front-row seat as huge, distant dust clouds, or nebulas, form new planets and stars. Astronomers call the nebulas “star nurseries.”
Here's what we already know. Teensy-weensy grains of space dust, called micrometeoroids, are much smaller than most of that other dirty stuff under your bed, smaller even than the width of a hair. They come from great distances, traveling at a rate of 150,000 miles per hour. At that speed, all that tiny stuff zipping through space can cause big damage to spacecraft and astronauts. Micrometeoroids are made of different chemicals and minerals than dust on Earth, and include traces of iron, diamonds, and gold. They even contain organic molecules, which are the particles that make up living things. This makes scientists wonder whether some of the ingredients for the first life on Earth might have arrived in space dust.
To discover all this, scientists have taken great pains to collect space dust for study. Aircraft and balloons flying 40 miles above the Earth gather grains on sticky collection plates. And on the ocean bottom, layers of dust from outer space have lain undisturbed for millions of years. Scientists scoop up samples and then separate out the precious cosmic grains using a magnet to draw out the particles with iron in them. (Earth dust contains little iron.)
A spacewalking astronaut adjusts the dust collectors on the Mir Space Station.
This tiny grain of space dust may once have been part of a comet.
Recently, NASA has launched missions into outer space designed to collect and study space dust well outside Earth's atmosphere. In January 2004, a small spacecraft called Stardust zoomed through the tail of a passing comet, gathering up dust samples from the tail and photographing the comet's head. Comets are believed to be frozen remains from the earliest days of the solar system, and dust from their tails will tell us a lot about how the system was formed. Stardust is the first such mission that will actually return to Earth, in 2006, so that scientists can study the samples firsthand.
“Don't Track that Moon Dust in Here!”
Our closest neighbor in space, the Moon, is pretty dirty, too. We know because we've been there. Between 1969 and 1972, six manned Apollo missions landed on the Moon. At first, scientists were worried. They knew the Moon's surface was dusty, but they didn't know how deep the dust was. Would a lunar lander sink out of sight? Fortunately not, and the astronauts got to work exploring. Over three years, they returned to Earth with 824 pounds of lunar rocks and soil samples.
Moon dirt, called regolith, is not at all like Earth dirt. Because the Moon has no protective atmosphere, space debris has rained down on it for millions of years, smashing its surface into a fine, shimmering dust. Much of the brightness of the Moon comes from sunshine reflecting off its sparkling surface.
Sweeping up the Moon? No, Apollo astronauts used special rakes to collect Moon dirt.
Unlike Earth dirt, Moon dust contains no life, and it is very light and annoyingly clingy. Astronauts complained that it got everywhere, even into their spacesuits and under their fingernails.
Nonetheless, this lifeless, bothersome stuff has a story to tell. By studying its chemistry, scientists know that the Moon was formed billions of years ago when the solar system was very young. A large object crashed into the baby Earth and sent a huge chunk flying into space. Captured by the Earth's gravitational pull, this chunk spun into orbit and became our Moon, whose dusty face still shines down on us today.
Dirt soon covered astronauts working on the Moon's surface, clinging to everything and generally getting in the way.
“The [Moon] dust…clung to everything. It got on every movable surface, it got in the suits, and when we got out of our suits in the spacecraft…it got in the pores of our skin and got under our fingernails…It took three months for lunar dust to grow out from under my nails…And it has a smell very few people, if any, have smelled on the Earth. It smells something like spent gunpowder, like you've just fired a shotgun or something and you can smell that powder.”
The Dirt on Mars
Mars is none too clean, either. Scientists believe that the Martian landscape was carved by erosion, and like Earth, its soil was created largely by the weathering of rocks. Every few years, dust storms four times the size of Texas blow wildly, pushing dirt all around the planet. Mars also has the largest volcanoes in the solar system, though they are no longer active. Huge eruptions long ago covered some of the planet with iron-rich clay, giving the surface its red color.
An enormous dust storm churns up Martian soil.
What else is in that Martian soil? Is it full of life like the soil on Earth, or is it dead and dusty like the Moon? Most intriguing, does it contain evidence of long-extinct ancient life? In 1976, NASA sent two spacecraft to Mars, the first to land on the planet's surface, to get a close look. Over the years, more probes followed, poking and prodding at the surface, scooping up dirt, and taking pictures. They began to find evidence that liquid water may have once been present on the surface. And where there is water, there may be life.
So, in January 2004, NASA launched two more landers, Spirit and Opportunity. They hoped further study of the chemistry of the Martian soil and rocks might finally solve the mystery of whether there had ever been water on Mars. Equipped with highly sensitive instruments, the spunky rovers drilled into rocks. They analyzed the soil's chemistry and even took its temperature. The soil appeared strangely sticky in places, like “clumpy cocoa powder,” and it was slippery, as the rovers discovered when they tried to climb small hills. At several locations the rovers “scuffed” the surface, digging trenches with their wheels to see what lay beneath.
The nimble rovers used their wheels to dig trenches and check out what lies under the soil's surface.
Scattered around them, the rovers found odd, blueberry-sized objects. These turned out to be made of hematite, a type of iron. On Earth, hematite can often be found at the bottom of a lake or in mineral hot springs in places such as Yellowstone.
Opportunity took this closeup of Martian soil, showing some of the strange, blueberry-shaped rocks.
Scientists are now studying in detail the data returned to Earth by Spirit and Opportunity, and we may soon know for certain about water—and life—on Mars. But there's nothing like the real thing, so NASA plans a mission to return some Martian soil to Earth in 10 years or so. We hope none of it ends up under your bed.
So, the next time you clean your room, as we know you must, just vacuum around the space dust. It has a lot to tell us.
What's almost lighter than air but tough as nails? It's an amazing substance called aerogel that scientists use to collect dust particles in space. Made from silicon and other chemicals, aerogel weighs less than any other solid on Earth. Though it looks like nothing more than blue smoke, a column of aerogel the size of a human could support the weight of a small car—about 1,000 pounds. To collect space dust, aerogel is attached to special equipment on board the spacecraft Stardust.
Particles of dust traveling 12 times faster than a bullet embed themselves in the aerogel and come to a slow stop, leaving carrot-shaped trails (right) and staying safe and sound until returning to Earth.
- A piece of rock that orbits the Sun.
- A mass of ice, frozen gases, and dust particles that travels around the Sun in a long, slow path. When a comet comes close to the Sun, it can be seen in the sky as a bright object with a glowing head and a long, streaming tail.
- Why are small particles in space sometimes dangerous to spacecraft and astronauts?
[anno: Small particles are sometimes dangerous because if they are going fast enough, they could tear through spacesuits or damage equipment.]
- Why do scientists want to study space dust?
[anno: Scientists want to study space dust because they hope to find out more about what space was like when the Earth was born. They also hope to learn more about what is happening in other parts of the universe.]
- Where has space dust and dirt been collected?
[anno: Space dust has been collected on the Moon, on Mars, from Earth's atmosphere, from outer space, from the tail of a comet, from Earth's ocean floors.]