2020 was an important year of deep space exploration for China, during which the first Chinese independent Mars mission Tianwen-1 and the lunar sample return mission Chang'E-5 were successfully launched. Tianwen-1 has combined three important functions:orbiter, lander and rover into one. Chang'E-5 is the first mission for China to return samples from other celestial body. On 17 December, it brought back 1.731 kg lunar sample successfully. 2020 was also a lunching window for Mars, which occurs every 26 months. In that window two other missions were also launched, i.e. the UAE's Hope Mars orbiter and the US's Mars Laboratory Perseverance. When deep space exploration became a focus of world attention, it is necessary to review the history and plan the future. This paper briefly reviews the history of human deep space exploration, discusses the scientific motivation and technical challenges. In particular, it discusses the sustainability of deep space exploration, and puts forward some relevant suggestions for the future development of China's deep space exploration.

deep space exploration  /  technical challenges  /  sustainable development path