After nearly 70 years of space exploration, Earth is now surrounded by space junk. Recently, an accident made the cleanup more difficult to start.
According to the European Space Agency (ESA), scientists plan on testing their "junk truck", ClearSpace-1, in 2025. It's a spacecraft with four arms that can catch debris (碎片) and bring it back to Earth. They have chosen to bring back VESPA, a 113-kilogram, two-meter-wide rocket part. However, in August, it was hit by another piece of space junk, creating new pieces. The ESA is now revising its cleanup plan.
Most satellites today are sent into Earth's low orbit, which reaches up to around 2,000 kilometers above the Earth. There, spacecraft are most likely to crash with each other. There may be as many as 170 million pieces of space junk in orbit. Big or small, any of the pieces can cause harm to a spacecraft.
In terms of the cleanup, scientists have some other ideas. One popular plan is to equip a spacecraft with harpoons (叉) and magnets (磁铁). The craft would shoot the harpoon to stick into the debris before "throwing" it back to Earth. Magnets could move the debris, changing its direction. The debris would burn after entering Earth's atmosphere so there wouldn't be much left when it reaches Earth. Scientists are also considering shooting lasers (激光) from spacecraft to heat up the debris' surface, creating a small push that would change the debris' orbit. This change would allow the debris to be caught by Earth's gravity.
Space junk can be very dangerous, and space agencies around the world are testing and planning the cleanup. But why haven't they done anything yet? One reason is the expense.
It would take between $4, 000 and $60, 000 per kilogram to catch one piece of debris larger than 10 cm. And around $300 million is needed to develop the laser technology.
