Der-shing Helmer’s Mare Internum is an ongoing hard-SF webcomic.
Doctor Mike Fisher is one of the elite few chosen to explore Mars, now in the initial stages of colonization. Or rather, he was. Bitter, alarmingly hostile, and socially isolated, he was fired after the loss of his artificially intelligent LEVi robot in the mysterious catacombs under the Martian surface. As soon as transportation is available, he will be sent back to Earth.
Before he goes, however, newly arrived Doctor Rebekah “Bex” Egunsola would like to take advantage of Mike’s EVA skills. Initially reluctant to venture back into the Martian caves, Mike allows himself to be talked around. It’s just one quick foray into the labyrinth. What could go wrong?