Don't Clean Your Room . . .

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.

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.

Dust Hunters

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.)

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.

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.

The Dirt on Nars

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.

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 dose 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.

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.

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.

Copyright Carus Publishing Company Jul/Aug 2004
Provided by ProQuest Information and Learning Company. All rights Reserved