When Project Apollo brought back lunar rocks and soil samples, it opened a new chapter of understanding Earth's lone natural satellite, a process that continues to this day, as old results are revisited and new techniques are used on existing samples. Topics such as the origin, evolution, structure and composition of the Moon, however, are still under debate.
Lunar research is still an active field of study. New technologies make it possible to continue to learn. But even so, the Moon continues to hold tight to some of its oldest and most cherished secrets. Foster examines many of the most interesting puzzles and what has been revealed by exploring them – as well as what questions remain.