Space is vast. Yet Earth orbits are becoming increasingly littered with debris (speckled graphic). A satellite could be demolished if struck by a 10-centimeter piece of junk, about the size of a softball. Even a one-centimeter tidbit could disable a spacecraft. And the more functioning, defunct or fragmented objects up there, the more that decay in the atmosphere (pink stripe). The collision problem has become so serious that in 2016 the European Space Agency (ESA), which tracks the objects, announced it might capture derelict satellites in low orbits, starting in 2023. Clutter is rising fast as more countries and companies launch electronics. In February 2017 India sent 101 shoebox-sized “cubesats” into a low orbit on a single rocket.

Credit: Jan Willem Tulp; Sources: “Space Debris by the Numbers” (information correct as of January 2018), European Space Agency; Space Debris: The ESA Approach. ESA Br-336. European Space Agency, March 2017 ; ESA Space Debris Office (raw data)