Hello,

 Astrobilology can be related to Physics. Physics and relative physics is the mantra. However, you also need to be in constant touch with chemistry, astronomy, biology, molecular biology, ecology, planetary science, geography, and geology.Prospective candidates in the field will need at least a bachelor's degree for entry-level positions. There are not many educational institutions that offer astrobiology degrees, so students will want to pursue degrees in astronomy, geology, chemistry, or related fields. More advanced positions require a master's or doctoral degree. Doctoral degrees are not available in astrobiology. Instead, prospective candidates will need to determine in what area of research, such as studying microbes in extreme environments, they want to specialize. The NASA Astrobiology Institute offers those in the field training, seminars, and relevant update.

 After completing your B.sc you should join any reputed institute for higher studies in Astronomy and then you can specialize in Astrobilology. Please keep in mind that NASA recruits people with outstanding Academic background and some experience in the same field with some research work or so on. 

Hope this helps