One of the things I liked most about Jill Tarter's interview was her willingness to answer questions with "I don't know" when it applied. That's not to say Dr. Tarter isn't an expert - her work in her field has been very influential, and I learned a lot about SETI from the interview. Instead, by the nature of her field, there are a tremendous number of both known-unknowns and unknown-unknowns, and she acknowledges this gracefully.
For example, when discussing the values for the terms in the Drake equation, she says "I don't know" and states that the error bars are just too large right now, and that more research is needed. Similarly, when discussing things like what alien signals might look like and how life might originate on other planets, Tarter similarly states that we just don't know enough. But that's exactly the reason we do science - to find out the answers to these questions.