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Abstract
As humanity’s ability to detect and mitigate threats from Near-Earth Objects (NEOs) improves, planetary defence has become a critical focus to protect Earth from potentially catastrophic asteroid impacts. However, the methods employed in planetary defence such as kinetic impactors, nuclear deflection and gravity tractors raise significant concerns regarding the environmental impact particularly the generation of space debris. Space debris which includes defunct satellites, rocket stages, and fragments from collisions is a growing problem that poses a risk to satellites, spacecraft and future space missions. The creation of additional debris from planetary defence operations could exacerbate this issue complicating the sustainability of space operations and increasing the hazards for other missions.
Kinetic impactors which involve deliberately colliding spacecraft with asteroids to alter their trajectory carry the risk of generating debris from the asteroids surface or fragments created during the impact. Nuclear deflection involving the detonation of a nuclear device near or on the asteroid, presents an even higher risk of fragmenting the asteroid into numerous smaller pieces further contributing to the space junk problem. The gravity tractor, a less violent method that uses a spacecraft’s gravitational pull to nudge an asteroid produces less debris but still poses the risk of collision with existing space junk.
The environmental and legal ramifications of these planetary defence methods are profound. Under international space law, particularly the Outer Space Treaty and the Convention on International Liability for Damage Caused by Space Objects, nations are held accountable for the damage their space activities cause including debris. The increasing risk of debris generated from planetary defence missions could lead to liability disputes and requires global cooperation in space traffic management. Furthermore, the long-term sustainability of space operations depends on minimizing debris and ensuring that planetary defence efforts do not undermine future space exploration or satellite functions.
To mitigate these risks strategies such as advanced modelling and simulation, debris removal technologies, international cooperation on debris management and the prioritization of non-destructive methods like gravity tractors are crucial. Effective collaboration between nations and space agencies is necessary to develop planetary defence systems that not only safeguard Earth but also preserve the long-term viability of space operations. This article discusses the complex balance between planetary defence and space debris, emphasizing the need for responsible planning and global coordination to ensure both Earth’s protection and the sustainability of space activities.