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Discovery of Earth-size planets rouses search for intelligent life

November 5, 2013 at 12:00 AM EDT
New data from the Kepler Spacecraft shows one in five of the sun-like stars in the universe have Earth-size planets. The potential for habitable planets has fueled excitement in the search for intelligent life. Jeffrey Brown speaks to one of the lead researchers, Geoff Marcy of the University of California, Berkeley.

GWEN IFILL: Finally tonight: The never-ending search for life beyond Earth just became more interesting. Scientists now say they think there are many planets, tens of billions, actually, beyond our solar system that feature at least some of the right conditions needed for life.

Jeffrey Brown picks up the story from there.

JEFFREY BROWN: A key condition, of course, is having the right surface temperature for water. Researchers identified planets in so-called Goldilocks zones, potentially habitable areas that are not too close to a sun-like star, making things too hot, or too far away, where it would be too cold.

To their astonishment, they found that one in five sun-like stars harbors an Earth-sized planet that may fit this category. The analysis came from data collected by the Kepler spacecraft.

Geoff Marcy of the University of California, Berkeley, is one of the lead researchers. He joins me from Mountain View, California.

And welcome back.

We have had you on this program in the past talking about the discovery of planets, so I was struck when you said about this new finding, “This is the most important work I have ever done.”

Tell us why? What’s the significance?

GEOFF MARCY, University of California, Berkeley: Well, you know, we have wondered for a long time, even going back to the time of the Greeks, whether there were planets around the twinkling lights you see in the night sky.

But the real question has always been, what about habitable planets, Earth-like planets that could support primitive life and maybe even intelligent life? And now for the first time, we have a census of stars showing that about one in five of the sun-like stars out there really do have planets the size of the Earth, the temperature of the Earth, and perhaps conditions conducive to life as we know it.

JEFFREY BROWN: And that’s what we mean by a habitable planet or potentially habitable, and this idea of a Goldilocks zone? 

GEOFF MARCY: That’s right.

Of course, the properties of a planet that make it suitable for life is — the basics have to be water, because our own human bodies are made of water. All life-forms on the Earth depend on water. And so we assume — perhaps incorrectly — that life out there among the stars would also depend on liquid water.

JEFFREY BROWN: So, how do you come up with this number of billions of potentially habitable planets? What — in layman’s terms, what does Kepler actually see?

GEOFF MARCY: What we have been surveying with the NASA Kepler telescope is 150,000 stars for four years. It was a brilliant stroke by NASA to build this new spaceborne telescope.

And we watch for stars that dim as the Earth-like planet crosses in front of the star, blocking a little of the starlight. And that census of 150,000 stars shows that about one in five of them has a planet the size of the Earth and the temperature of the Earth. 

JEFFREY BROWN: Now, there are caveats, even a number of caveats. Right?

Tell us what we — tell us what we don’t know about these planets and whether they’re, in fact, suitable for life.


This is the $64 million question. Do these planets that orbit their stars in orbits that remind us of the Earth, the size of the Earth, do they actually have liquid water? Do they have lakes and oceans within which the biochemistry of life could flourish? Do they have atmospheres that are conducive to life? Do these planets have a moon that might stabilize the spin of their planets? So there could be properties of planets that render them suitable for life that we don’t even know about.

JEFFREY BROWN: And, of course, they’re rather far away, right? So it’s going to be hard to verify.

GEOFF MARCY: Well, one tragedy is that the stars we have been surveying are 1,000 light-years away. Even traveling like the Voyager spacecraft, as its speed, it would take millions of years to get there.

But the key is, if one in five stars has an Earth-like planet, you only have to travel out a few light-years to encounter the nearest five sun-like stars. So one of them within spitting distance may have an Earth-like planet.

JEFFREY BROWN: And the future — the future work at least for now has to happen without Kepler, right, which is out of commission?

GEOFF MARCY: We are very excited about a possible revamping of Kepler.

Kepler has only two reaction wheels left to stabilize it, but it can still work. And so the scientists at NASA Ames Research Center are working very hard to revitalize Kepler so that it can continue hunting for Earth-like planets.

JEFFREY BROWN: And what does happen next for you and other researchers?

GEOFF MARCY: Well, the most exciting thing I think for the future is to actually search for intelligent technological life on any of these planets. Are there intelligent beings there? Maybe we can pick up the Andromeda “NewsHour” from Alpha Centauri and pick up their radio and television transmissions.


JEFFREY BROWN: I would like to — I would like to hear that, actually, yes, see what they’re doing on Andromeda.


GEOFF MARCY: Right. Right.


JEFFREY BROWN: Well, is this — is this — finally, is this something that you and I are likely to learn about, or are we talking generations from now before mankind, humankind, is able to pick up that kind of communications?

GEOFF MARCY: There are scientists working day and night right now using radio telescopes, optical telescopes, infrared telescopes, hoping to pick up the laser communications, the radio transmissions from any other intelligent civilization.

So it’s possible that in the next few years or decade, there could be the first detection of intelligent life elsewhere in the universe.

JEFFREY BROWN: All right, Geoff Marcy of U.C. Berkeley, thanks so much.

GEOFF MARCY: My pleasure.