Wanted! Garbage collectors in space
By Stephen Ornes / September 21, 2011
Using telescopes on Earth, space agencies track large pieces of debris orbiting the planet. Most of the garbage is in low-Earth
orbit, or LEO, which extends as high as 2,000 kilometers (1,243 miles) above Earth’s surface. This is an artist’s conception of
space junk; the sizes of the pieces are greatly exaggerated. Credit: ESA
Every messy kid gets told to clean up his or her room. City governments send out trucks and crews to clean up roads
and parks. Now, scientists say if we want to keep our astronauts and satellites safe, it’s time to clean up space, and soon.
A sprawling garbage heap floats high above Earth. It contains fragments of broken-down satellites and pieces of used rockets,
as well as a few unusual objects like gloves and cameras accidentally dropped by astronauts. The problem isn’t going away; it’s
getting worse. The number of pieces of space garbage gets larger every year. Around the world, space agencies worry about the
trash because even small bits of litter — no larger than the fingernail on your pinkie — can cause serious damage to satellites or
spacecraft.
In a recent study, engineer Hugh Lewis and his colleagues from the University of Southampton in England ran some
calculations on space junk. In August, they reported that the growth of space junk could slow down if every year about 10 large
pieces were removed. (The largest piece of space junk is about the size of a refrigerator. If a broken or defunct satellite doesn’t
fall back toward Earth and burn up in the atmosphere, it continues to whiz around our planet. It may crash into another satellite
or used rocket and break into smaller pieces. These pieces are called orbital debris. In February 2009, a Russian satellite and a
U.S. satellite plowed into each other over northern Siberia. The collision resulted in more than 2,000 new pieces of space junk
that continue to orbit Earth. NASA’s Orbital Debris Program Office tracks the larger of these pieces to make sure they don’t
smash into other satellites.
In March of this year, scientists saw that the International Space Station was headed toward a four-inch piece of space
garbage left over from the 2009 collision. They sounded the alarm, and in April the space station changed its course to avoid
the debris. This was the fifth time in less than three years that the station has changed its course to stay safe from floating
debris.
Not all space junk stays in space. In January 2001, this heavy chunk of a Delta 2 rocket fell to earth about 240 kilometers (150
miles) from Saudi Arabia’s capital, Riyadh. Credit: NASA Orbital Debris Program Office
Another situation, related to greenhouse gas emissions, is lengthening how long any piece of space trash remains in
orbit. As things in orbit push through Earth’s atmosphere, they slow down. This braking action, called friction, not only lowers
the orbit of space junk but also increases the chance it will burn up as it slows down. Friction is currently the only thing that
removes space junk from orbit. But as more emissions of carbon dioxide, a greenhouse gas, rise into the upper atmosphere, this
gas cools off a layer called the thermosphere. As a result, the thermosphere is becoming less dense. (Density is the amount of
matter packed into a particular volume, and materials with more density are thicker. Maple syrup, for example, is denser than
water.) The drop in density means there’s less friction on space junk, allowing the trash to orbit longer. And this increases its
opportunity to hit something.
The recommendation by Lewis and his team to send up space-garbage collectors is easier said than done. Scientists
can’t remove 10 pieces a year because “we don’t know how to clean up even one,” Nicholas Johnson told Science News.
Johnson is the scientist in charge of NASA’s Orbital Debris Program Office, which keeps track of large pieces of debris and
helps spacecraft and satellites avoid dangerous situations. He said that even though a space cleanup is “desirable,” it’s not going
to happen in the next few years. “There’s nothing on the horizon” for a space trash pickup program, he said.
Right now, the risk of a serious collision is low. Since people began sending rockets into space, Johnson said only two
operational satellites have ever been damaged. He said it’s possible that a dangerous or deadly collision could occur, but the
chance of that happening is small.
For now, Johnson told Science News, his team’s near-term priority is tracking smallish pieces of space debris. There
are more of them, they’re harder to see from Earth and they’re more likely to cause trouble.
“If we’re going to lose spacecraft in the next two decades,” Johnson said, “we’re [probably] going to lose them to small things
we [currently] can’t track.”
POWER WORDS (adapted from the New Oxford American Dictionary and NASA.gov)
atmosphere The envelope of gases surrounding Earth or another planet.
debris Scattered fragments, typically of something wrecked or destroyed. Space debris includes the wreckage of defunct
satellites and spacecraft.
density A measure of the consistency of an object, found by dividing the mass by the volume.
friction The resistance to movement that occurs when two things — solids, gases, liquids or a combination of two of these —
are in contact. Friction generally causes a heating, which can damage the surface of the materials rubbing against one another.
orbit The curved path of an object or spacecraft around a star, planet or moon.
thermosphere An upper region of the atmosphere that extends to nearly 400 miles above Earth’s surface. In the thermosphere,
temperature increases with height because of the sun’s energy.
Remember to answer the questions in COMPLETE sentences and provide details!
1. What are some of the objects that make up “space junk”?
2. What are the dangers if space junk stays in orbit and continues to build up?
3. What is the only thing that can slow down space junk?
4. Explain how the greenhouse effect is affecting space junk. BE DETAILED!
5. What plans are in place right now to try and remove trash from space?
6. What ideas do you have on how to remove space junk?