The first thing I would do is try to get out of the responsibility. It will be difficult for me to take responsibility of something that is not my field of expertise. What if I mess up and my mistakes end up costing the company I work for? So, if possible, I will try to get out of the responsibility first. 

If that doesn't work, then my next move would be to study and learn as much as I can about the project. After that, I will surround myself with people who are experts on the field. I will make sure that I choose a team of qualified experts for the project and empower them to be able to the work effectively.