Over the Milky Way — Diane L. Nees

Chi and Nikea are not only brother and sister; they are friends. Together they explore their planet, Zeptune, and enjoy playing space games. Nikea has a great zest for exploration and this time she decides to daringly jump craters. She pushes her luck and finds she has a huge problem on her hands. Who can help her? Who will help her? She feels very alone. But, even in outer space, Nikea finds that 'alone' does not really exist... and she is forever grateful.