Before Mars (Planetfall, #3) by Emma Newman

After months of travel, Anna Kubrin finally arrives on Mars for her new job as a geologist and de facto artist-in-residence. Already she feels like she is losing the connection with her husband and baby at home on Earth–and she’ll be on Mars for over a year. Throwing herself into her work, she tries her best to fit in with the team.

But in her new room on the base, Anna finds a mysterious note written in her own handwriting, warning her not to trust the colony psychologist. A note she can’t remember writing. She unpacks her wedding ring, only to find it has been replaced by a fake.

Finding a footprint in a place the colony AI claims has never been visited by humans, Anna begins to suspect that her assignment isn’t as simple as she was led to believe. Is she caught up in an elaborate corporate conspiracy, or is she actually losing her mind? Regardless of what horrors she might discover, or what they might do to her sanity, Anna has find the truth before her own mind destroys her.