Is finding another Earth within our reach? Dr. Sara Seager says yes. Image credit: NASA/Ames/JPL-Caltech
Is finding another Earth within our reach? Dr. Sara Seager says yes. Image credit: NASA/Ames/JPL-Caltech

What does it take to find life in the universe? Dr. Sara Seager of MIT is working hard to find out. Seager was recently interviewed by NPR’s Science Friday at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Sara believes the current search for exoplanets has broader implications for our future. “It’s a special time for us here on Earth. It’s the first time in human history that we actually have the technological capability to find other Earths, to identify them as Earths, and to hope to look for signs of life on the first handful or the first dozens or hundreds of exoplanets, and that’s a special time in history. So I’m trying to do what I can to make sure that happens now.”

Where are we in the search for exoplanets?

Recently teams of scientists determined that one in five sun-like stars likely have an Earth-sized planet in the habitable zone. According to Seager, “all evidence points to the fact that small planets are extremely common, they are literally everywhere.” How many planets have we found? It depends on how you count them, but, Seager said, “the better statement for everyone is we’re confident that every single star in our Milky Way galaxy has at least one planet.”

How do we look for life on other planets?

We will look for life by peering into the atmospheres of exoplanets in an effort to find gases that don’t belong. For example, on Earth oxygen is 20 percent of our atmosphere. If we didn’t have photosynthetic processes (used by plants and other organisms to convert sunlight into energy) then the level of oxygen in our atmosphere would be almost zero. There are a variety of gases the scientific community is considering as important in the search for extraterrestrial life.

One way in which Seager thinks we could accomplish this is through direct imaging with a starshade, "a big, big 30 meter shade that will fly tens of thousands of kilometers from a telescope … it would search nearby stars directly for an Earth and it would be able to get the spectrum and to see if there’s life there.” The starshade allows us to image planets by blocking out the bright light of the parent star. It is one concept currently being studied by NASA to image the atmospheres of exoplanets. Another is a coronagraph that is internal to the telescope.

What do we do if we find a planet with life?

Even if we find evidence indicating that life may exist on another planet, we won’t be able to tell if life is basic, complex, or intelligent. But it will give us a start on answering the question of whether there is intelligent life. 

Additionally, Seager said we could feasibly communicate with another planet (SETI for example), but that it would be a slow conversation. If a planet is ten light-years away, it would take ten years for our message to be delivered and then another ten years for a reply if they answer right away.

For more discussion on these topics and more, listen to the entire Science Friday interview here: