So I went down this rabbit hole a while ago, because the ending of 'Mariposa 1' left me with so many questions. From what I could dig up, there isn't a direct, titled 'Mariposa 2' sitting on a bookstore shelf. The author seems to have explored related ideas in other works, but as a sequel, it's a bit of a 'maybe, but not really.' I kept searching forums and old blog posts, and the consensus leans toward it being a standalone. It's a shame, because the world-building hinted at so much more—I really wanted to know what happened after that final, ambiguous scene with the signal from the nebula. Sometimes a story's power is in its singularity, I guess, even if it leaves you wanting.
That said, if you're craving more of that specific vibe—cosmic mystery with a touch of body horror and deep-space loneliness—I'd point you toward things like 'The Last Astronaut' or some of Jeff VanderMeer's short stories. They scratch a similar itch, though they're obviously not the same characters or plot. The author's other novels might have thematic echoes, but 'Mariposa 1' feels like its own unique creature. In the end, you just have to sit with its haunting, open-ended finish.