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Full Transcript (below)
7. Q: How can you be sure you have discovered a life form or not? Is there some kind of threshold that you can use to help you decide if your data indicates life or not?
Stoker: "It's, ah, really a new area in scientific research to try to understand how do you look for life on another planet. What things do you look for? What things would be a positive detection? What things would not be a positive detection? Um, and we're taking some kind of baby steps in that direction. I cannot say that we have solved the overall problem. But a lot of work is going on right now in terms of trying to develop instruments that are sensible ways to look for life on another planet. And, these are some of the instruments that are under development that we will be using. Ah, if you go back to the one time that NASA ever tried to search for life on another planet – it was done with the Viking experiments in the 1970s. And the, ah, question of how do you determine when you have a positive detection is a very important one because, ah, there's – if you were to do this on Earth, you could do other experiments to try to test if you are – if the experiment you used was giving you accurate results. You can do what we call ground truth. You can do other experiments to back it up. And in practice in our upcoming field test, that's what we will do. We will do other experiments to determine that we're getting accurate results. But if you were to do this on Mars, you can't do that. You can't do other experiments to test whether your mechanism is working properly, or whether you got a false positive, for example. Um, the Viking experiment had flew three life detection packages. And they had a requirement that all three life detection packages gave positive results in order for them to believe that they had found life. And that criteria was never met. Um, but that was an attempt to say how do we know when we really have a positive? " (2:07 MINUTES)