A trilogy of novels co-written by Ryk E. Spoor and Eric Flint: Boundary, Threshold, and Portal. A discovery of an aeons-old alien base on Phobos with connections to a mysterious fossil sends paleontologist Helen Sutter and a crew of associates on a mission of exploration through the Solar system, first to Mars and Phobos, then to Ceres, Jupiter, and beyond.
Tropes in the Boundary series:
- Canis Latinicus: Finding a mysterious fossil of a never-before-seen organism, Helen Sutter names it Bemmius Secordi. The Secordi is for the Secord family, on whose land it was found. Only a few people catch on that the Bemmius is her covert reference to "Bug Eyed Monster", as she's convinced it's the fossil of an alien but which isn't something she dares state publicly.
- Contemptible Cover: He gets annoyed every time someone brings up the Flame-Farting Tyrannosaur cover from Boundary.
- Cool Starship: The Nebula Storm.
- Cult: Madeline's parents were members of one.
- Designated Victim: Boundary incorporates the Baen Books house joke of killing off Joe Buckley. In this book, it's subverted — despite teasing his impending doom from the very first sentence, and on multiple occasions since, he survives.
- Did Do The Research
- Driven to Suicide: Richard Fitzgerald in Threshold, after being ejected into space with no hope of rescue.
- Everything Sensor: The Fairy Dust is a relatively realistic version.
- He Is Not My Boyfriend: A.J. and Jackie are two scientists who work together and are friends; they also bicker a lot. As such, Jackie always gets ribbed by the other people in their team about her "boyfriend" A.J. She vehemently denies these accusations to the knowing reaction of the others. Ultimately subverted, as A.J. ends up with Helen, and Jackie smugly declares to everyone within hearing distance, "I told you he wasn't my boyfriend."
- Load-Bearing Hero: A cave-in in an ancient ice tunnel. Luckily, Madeline's spacesuit could become rigid on command, so the problem was merely replacing her with other bracing.
- Nanomachines: "Fairy Dust". Also once used by the Bemmies for their slate displays and dusty plasma drive.
- Phlebotinum Killed the Dinosaurs: It appears the asteroid which killed the dinosaurs was a weapon launched by the Bemmies.
- Shout-Out: to Fullmetal Alchemist, Saint Seiya, and Elf Princess Rane/Fairy Princess Rēn, for starters.
- The Sociopath: Richard Fitzgerald