Earth's orbit is getting crowded. Last year, a record 2,409 objects were sent to orbit, the bulk of which were satellites settling into the increasingly cluttered region 1,200 miles above our planet's surface known as low Earth orbit. Another 2,000-plus satellites have joined them so far this year, according to the UN's Online Index of Objects Launched into Outer Space. As the presence of artificial objects in orbit grows, so too does the accumulation of debris, or space junk -- and the risk of collisions. Dealing with existing waste and preventing its unchecked growth has become imperative, but it's a problem that doesn't have one simple solution. Currently, the US Department of Defense's Space Surveillance Network tracks more than 25,000 objects larger than 4 inches wide, most of which are concentrated in low Earth orbit, and there are an estimated millions of smaller objects still that are trickier to pinpoint.

As the space race heats up, debris has become a burning issue. Since the beginning of the space age in the 1950s, thousands of satellites and rockets have been sent to space and are marooned there. The Union of Concerned Scientists Satellite database has listed more than 4,084 operational satellites currently orbiting the Earth. In 2010, this number was less than a thousand. In the distant future, this problem can extend to the lunar surface and the asteroid belt (the current count stands at 34,000 pieces of space junk bigger than 10 centimetres in size and millions of smaller pieces).