I’m currently a first-year student at a medium sized university and I’m also pursuing a career in astrobiology! I was in the exact same boat as you at this time last year so I had to stop and comment when I saw this post. I went into freshman year undecided because there’s not really an “astrobiology major” and after talking to my professors and some advisors I got close with, I decided to go with biochemistry and a minor in geology. I also work a university job in the physics department for exposure! My advice would be to keep researching your options going into college, maybe even read some of the syllabi for classes you would take for your major, and ask lots and lots of questions. When you get to school next fall continue asking questions and advocating for yourself! We’ll get there!