ROBERT SIEGEL, HOST:
And one more question about the search for more planets like Kepler-452B - why? Katie Mack is an astrophysicist at the University of Melbourne. She happens to be in Oxford in England today. Welcome to the program, and tell us why keep looking for planets that might be sort of like Earth.
KATIE MACK: Well, I think that we're naturally curious about what else is out there. And looking for planets like the Earth gives us an idea of how special our planet is, how special life might be. So if we find planets that look like Earth, then that might give us a clue to, you know, where we might also find life like ours.
SIEGEL: So is news of Kepler-452B exciting for you?
MACK: You know, every new planet is exciting to me. I have an app on my phone that gives me a notification every time we find a new exoplanet. So each time, you know, we're getting a little bit closer to what we think might be the best possibilities for life out there. And this planet is one that has a lot of similarities to the Earth and to the Earth-Sun system, so it is always exciting.
SIEGEL: Well, let me ask a question. Is it possible that astronomers have overlooked a planet that's just as much like Earth as this one but a lot closer?
MACK: Well, this particular kind of observation requires the planet to pass right between its start and Earth. And so if the planet is orbiting in a different plane, then we might not be able to detect it with these kinds of methods.
SIEGEL: Given that a major question here, as you describe it, is, how rare is life as we know it, and is there life out there in a similar planet, what would it take to detect what kind of life might conceivably exist or have existed on a planet out there?
MACK: Well, the main thing that we need to do is study the chemistry of the atmosphere of a distant planet, and that's difficult to do. But we're starting to be able to have the technology to do that in certain situations where we can actually directly image the planet. And this isn't a situation where we're going to be likely to be able to do that, but as we find more and more exoplanets, we'll have more examples of other atmospheres. And what we really look for in other atmospheres is a sign that the atmosphere is out of equilibrium in some way where you would need to have life changing the chemistry of the atmosphere to get that mix of elements. We're starting to be able to do that, but at the moment, we haven't seen anything that really stands out as that's something can only happen with life.
SIEGEL: It sounds like the kind of work that you're talking about involves posing a question in the 21st century that might not be answered until the 23rd century. I don't know. Is that inspiring or frustrating? How do you deal with that?
MACK: (Laughter). Well, I'm a cosmologist, so I think about things that are, you know, billions of years old or billions of years in the future. So that's normal for me. But I think that we're actually closer to finding this out than we might think. The observations that we need to do to study other atmospheres - some of those are happening. We've seen planets where we have indications of clouds. We've been able to look at the chemistry of atmospheres of planets around other stars, so it's not that far off.
I think the thing that is really far off is traveling to any of these other planets. I think that's the sort of thing where, you know, it would take technology far beyond what we have, and it would take extremely long times. But in terms of actually finding signs of life on other worlds, I think we're getting pretty close to being able to do it. So I think that we have a chance of finding that out within our lifetimes.
SIEGEL: Katie Mack, thank you very much for talking with us today.
MACK: Thanks for having me.
SIEGEL: Katie Mack, astrophysicist from the University Melbourne, spoke to us from Oxford, England. Transcript provided by NPR, Copyright NPR.