Star Challengers Trilogy: Moonbase Crisis, Space Station Crisis, Asteroid Crisis (Volume 4)

After an exhilarating field trip to the local Challenger Center, JJ Wren and her friends are hand picked by the mysterious Commander Zota to become Star Challengers—sent into the future on special adventures to a moonbase, a space station, and the asteroids. Their mission is to learn high-tech skills . . . and save the human race from an imminent alien invasion!