1. Garbage

    Space Junk Crisis Looming

    NASA / AP Photo

    You won't see this on space tourism brochures. A report by the National Research Council says space debris has reached “a tipping point." It's crashing into other debris, creating dangerous levels of orbiting fragments. There are 22,000 pieces of debris orbiting the Earth that are large enough to be tracked from the ground, and many more smaller objects, some of which fly at 17,500 mph. Orbiting debris could pose a risk to satellites and astronauts. The report refers to a study by the Defense Advanced Research Projects Agency that proposes nets and umbrella-shaped devices that would sweep up debris.

    Read it at BBC