To explore higher, farther, and faster, scientists and engineers have developed advanced materials for manned spacecraft and satellites for a range of sophisticated applications in transportation, global positioning, exploration, and communication. Materials used in space are exposed to vacuum, intense ultraviolet radiation from the sun, and ionizing radiation that results in material damage as well as charging (electrostatic discharge effects), micrometeoroids and debris impacts, and thermal cycling (typically from -175 to 160°C). In terms of materials degradation in space, the low Earth orbit (LEO), where LEO is defined as 200—1000 km above the Earth’s surface, is a particularly challenging synergistic environment, since atomic oxygen (AO) is present along with all other environmental elements. Hence, this special issue focuses primarily on the materials issues experienced in LEO by space environmental exposure, such as on the exterior of the International Space Station and the Hubble Space Telescope, and the challenges and opportunities of ground-based laboratory sources to mimic LEO. The combination and comparison of both in-flight and groundbased experiments are needed for the development of predictive understanding of the materials degradation and AO passivation mechanisms in LEO. Such insights are essential for the development of advanced materials and coatings to ensure the longterm durability and performance of vehicles employed in space.