Space debris, also known as space trash, is the waste of human space activities and the main source of pollution of the space environment. With the increasing frequency of space activities, space debris is increasing day by day, posing a serious threat to spacecraft in near-Earth space. Falling into the atmosphere will pose a serious threat to the safety of life and property on the ground. In particular, when a nuclear-powered spacecraft falls, it will cause chemical and radioactive pollution to the environment, with serious consequences. The focus of this passage is (). ['What is space debris.', 'Why space debris is increasing.', 'Space debris is a major source of pollution of the space environment.', 'Space debris concept and its serious harm.']