Second objective: mitigating outer space derelict objects

Before calling these relics ‘space junk’, it must be remembered that mass and space exploration are not compatible: a spacecraft can’t afford trailing unnecessary load, so items that are no more useful at one point into the mission become dead weight and must be shaved off quickly. For instance, the Apollo astronauts couldn’t clean up the ALSEP sites and bring back home all the packaging (see picture above): if they had done so it would have been at the expense of the precious lunar rocks and their very short time on the surface doing science. As of today, there is no other viable option to guarantee mission success and there are no means to retrieve them.

Thus, ‘derelict objects’ is a more appropriate word to qualify them and they can be classified into three groups:

  • Group 1: items that are inert and immobile, for instance aluminum parts or soft bags. As the space environment is harsher than their individual impact on it, they can be classified as ‘visual annoyance’ (see the Apollo 17’s ALSEP site in the picture above);
  • Group 2: chemically active items (e.g. spacecraft batteries or propellant tanks) that can induce pollution in probable organic or icy worlds such as Venus, Mars, Gas Giants’ Moons, dwarf planets, comets and some asteroids;
  • Group 3: items that are travelling at orbital speed in the solar system. As they represent a threat to space navigation and to the surface of celestial bodies, they can be classified as hazardous objects.
  • While all cases should be remediated, both latter groups must be emphasized to mitigate consequences. This catalogue is a step in this direction.