Do I have a chance of getting on the Mars mission?

I plan on being a doctor in the future, preferably a neurosurgeon which have the most training and most knowledge of medicine, I am wondering that if I become an experienced doctor if NASA would hire me to be a part of the Mars mission. I can't see a 2-year space mission leaving without a doctor. I will be 32 when I am a neurosurgeon and it will be the year 2028.