Adventure.

There are a lot of facts to be known in order to be a professional anything — lawyer, doctor, engineer, accountant, teacher. But with science there is one important difference. The facts serve mainly to access the ignorance… Scientists don’t concentrate on what they know, which is considerable but minuscule, but rather on what they don’t know…. Science traffics in ignorance, cultivates it, and is driven by it. Mucking about in the unknown is an adventure; doing it for a living is something most scientists consider a privilege.

Brain Pickings has a great review of Stuart Firestein's book, Ignorance: How It Drives Science, here.