Read the passage below carefully, and then choose the best answer:
Space Debris
Once something is considered rubbish, we want to throw it away and forget about it. Yet if we are not careful about where we store it, our garbage could come back to haunt us. On the Earth, poorly discarded garbage can cause land, water, and air pollution. And now, people are starting to learn that space debris can also cause a host of different problems. Space debris is defined as a collection of objects that orbit the Earth. Space debris can be classified into two categories. One is man-made rubbish, such as old satellites, rockets, and other machinery left in space after past missions. The other is natural objects, such as meteors that are traveling through space. If you think the man-made garbage doesn’t amount to much, guess again. Researchers estimate that there are over 20,000 pieces of large debris floating around in space and approximately 300,000 smaller pieces in orbit as well. Traveling at speeds of up to 17,500 miles per hour, these objects create a great degree of danger for any spaceships when they leave or return to the Earth. We are lucky to some degree that there haven’t been too many accidents caused by space debris as of yet. Still some incidents have occurred. In 1996, a French satellite was damaged after it crashed into debris from an old French rocket. Then in 2009, an old Russian satellite collided with a working US satellite. The end result was an additional 2,000 pieces of space junk that was added to the junk pile. As the current situation can only worsen, it is now up to the international community to cooperate and create a plan to deal with space debris. For starters, several nations have pledged to take more care with the items they discard in space to cut down on future debris. Researchers are working on devising a way to label space junk, so it can be avoided. Others have proposed more creative techniques to recapture the garbage and discard it on the Earth, or destroy it with lasers. The nightmare scenario that everyone fears is if the Kessler Syndrome starts to occur. This is when the density of garbage becomes so high that it sets off a chain reaction of collisions which would raise the probability of accidents even further. Although there is not a long-term solution in place for space debris, nations are starting to understand the seriousness of this problem.
1. Space debris is _________ the Earth.
