Landing attempts on Mars and a comet have proven to be incredibly arduous, and the moon’s unique topography comes with its own difficulties. “It’s a complex engineering undertaking to not only design the vehicles to get to the moon, but to design the control systems that have to work autonomously and that have to be able to account for the limited atmosphere, rugged terrain, the variation in lighting. All of those have to be taken into consideration in concert,” says Ron Birk, a development executive at the Aerospace Corporation, a nonprofit think tank, and president of the American Astronautical Society.