Complete the statements. Choose the correct answer.
1. Most space debris is created when satellites _______.
A. stop working
B. fall back to Earth
C. collide or explode
2. Debris _______ in a large debris cloud.
A. falls to Earth
B. orbits Earth
C. travels into deep space
3. Falling debris _______.
A. sometimes causes injury to people on Earth
B. frequently falls into cities and towns
C. usually burns up before it reaches the ground
4. Debris fragments in space are dangerous because they _______.
A. travel very fast
B. all move in the same direction
C. orbit close to Earth
5. _______ must cooperate to solve the problem of space debris.
A. Scientists and researchers
B. Governments and businesses
C. The international community
Transcript
Reporter: When NASA announced in 2011 that an old weather satellite-a six-ton piece of space junk, the size of a bus, was falling back to earth, people worried. Scientists knew when it would fall, but not where. As it turned out, it came down harmlessly in the Pacific Ocean. But this made us wonder: How much space junk is up there? And are we in danger?
Michaela Johnson: Well, we call it orbital debris, not space junk.
Reporter: That’s Michaela Johnson, a scientist who studies debris in space.
Michaela Johnson: Most of it’s created when satellites collide or explode. Two recent events created one third of the debris now in space: In 2007, an old Chinese satellite exploded. And in 2009, an old Russian satellite hit an active American satellite.
Reporter: NASA tracks 21,000 large fragments – fragments more than 10 centimeters in width, or the size of a large apple. But there are 500,000 smaller fragments-the size of a grape – that we can’t track. And the number of tiny particles, less than 1 centimeter, could be in the hundreds of millions. All these fragments orbit the earth in a giant debris cloud. We’re looking at a map of the debris on a computer screen.
Michaela Johnson: So, this is the earth. And you see here, each dot is a piece of debris larger than 10 centimeters.
Reporter: So far, no one has been injured or killed by space debris falling to Earth.
Michaela Johnson: Most of it burns up long before it reaches the ground. But on average, one piece of space debris falls to Earth each day, usually in the ocean or a place where no people live.
Reporter: A bigger problem is the fragments in Earth’s orbit. These fragments are dangerous because they travel incredibly fast, about 8 kilometers per second.
Michaela Johnson: That’s eight times faster than a speeding bullet.
Reporter: At that speed, even small fragments can do serious damage to a spacecraft. And with each collision, more debris is created, increasing the chances of another collision. The problem will only get worse unless we can stop the creation of more space debris. And with over 1,000 working satellites in orbit, we might all feel the effects.
Michaela Johnson: Our communication satellites, our weather satellites, our navigation satellites are all in danger.
Reporter: That means our phone calls, TV signals, weather reports, and GPS map systems.
Michaela Johnson: And it’s not just a U.S. problem, it’s an international problem. Every country that sends a spacecraft or satellite into space, we’re all part of the problem. So the international community needs to cooperate. We have to stop creating new debris, and to clean up the debris that’s already there.
Reporter: There is some progress. Space agencies from 12 countries have formed an organization, the Inter-Agency Space Debris Coordination Committee, to find a solution. But until then, we’ll keep an eye on the sky. Just in case.