The Growing Problem Of Space Junk

(CNN) More than 3 million years ago, members of an unknown hominin species sat on a river bank at the site of Lomekwi, in what is now Kenya, and made a set of stone tools for their daily tasks. Only a trained eye can distinguish the detritus they left behind from naturally broken rocks. In the intervening millennia, human trash has grown in complexity and quantity, introducing novel materials like plastics and metal alloys. What humans discard is fodder for archaeologists, but it's also an environmental problem that is becoming interplanetary. The Soviet satellite Sputnik 1, which launched on October 4, 1957, was the first human-made object in space. It kick-started the space race and inspired dreams of holidays on the moon and Martian colonies. But the satellite's orbit decayed just three months later, and it burned up as it reentered Earth's atmosphere. It was the first piece of space trash. Nothing survived of the basketball-sized aluminum sphere with distinctive antennas. That's not likely to be the case for the Long March 5B rocket, which is expected to fall back to Earth this weekend after delivering the Tianhe module of the new Chinese space station to orbit in April. It's one of the largest uncontrolled space objects to fall out of orbit. The rocket uses cryogenic fuel, so its fuel tanks are extremely robust to contain liquid oxygen and hydrogen under high pressure. Based on my observations, fuel system components are the most common rocket element to make it back to Earth. Source