In the next decade, NASA aims to launch humankind toward the moon and on to Mars—a monumental step in crewed space travel. Such a journey is filled with challenges and perils, not unlike those faced by the first explorers to cross the ocean. However, instead of stormy seas, these explorers will set sail amid the hazards of the heliosphere—the magnetic environment emanating out from the sun and encompassing the solar system. The risks of travelling through this realm ultimately ride on how well we can understand the dynamics therein.