The Temporal Expeditions

Sandy Lombardia's wealthy family pressed her into the field of physics, to join other family members in furthering the secret development of time travel technology. When a monstrous asteroid emerges from deep space on an impact course toward Earth, Sandy is chosen to launch two expeditions into the past. She is also chosen to lead an expedition of naval ships. The expeditions goal is to escape extinction; their mission is to prepare humanity for the future.