Fifty years ago, in July 1969, the Apollo 11 lunar module landed on the Moon and humans left their first mark on the surface of another world. In this special issue of Science, a Review, Policy Forum, Feature from Science's news department and an Editorial by Science Editor-In-Chief, Jeremy Berg, celebrate the semicentennial anniversary of the landing, its scientific impact and explore the potential future of lunar exploration.
In the Review, Richard Carlson highlights the discoveries and contributions to planetary science that were made possible through the study of lunar rock samples returned to Earth by the Apollo and Luna missions. Because Earth is so geologically active, nearly all of the material on its surface has been recycled and reformed anew. As a result, what little evidence remains from the planet's earliest days is often difficult to discern from more recent geological events. Many of the Moon's features, however, have been preserved since the Solar System's formative years more than four billion years ago. Prior to the Apollo landings, it was widely thought that planets formed cold and as a result of the gentle accumulation of asteroid-sized debris. However, the samples retrieved from the Moon illustrated a dynamic and far more violent process, characterized by high energy impacts and global-scale melting of rocks and minerals. Lunar samples have also been used to develop a chronological record of cratering on the Moon's surface. This record forms the foundation for the age estimates of other planetary surfaces throughout the inner Solar System and the dynamic planetary interactions with the space environment. As analytical technologies and techniques continue to advance, Carlson suggests that the lunar samples brought to Earth a half-century ago will continue to provide new insights into the formation and geology of other worlds.
A Policy Forum by Chunlai Li and colleagues highlights some of the most recent lunar exploration missions. Earlier this year, the China Lunar Exploration Program's (CLEP) Chang'E-4 lander and Yutu-2 rover landed on the far side of the Moon. The authors discuss China's lunar exploration program and its goal of understanding the Moon through advances in space technology and international collaboration. Although still in its infancy, the CLEPs four lunar missions so far have built a foundation for subsequent lunar exploration. According to the authors, future missions are being developed to fly in the next decade and CLEP will develop its capabilities for both robotic and human exploration of the Moon's surface.