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'We're Looking for Chemical Fingerprints of Life'

NASA stargazer Natalie Batalha on the discovery of a new Earth and the demographics of the galaxy.


This is "Think Tank," an occasional series of conversations with Bay Area power players, conducted by San Francisco editors. Interviews have been condensed and edited for clarity.

Name: Natalie Batalha
Job: Research astrophysicist at NASA's Ames Research Center; Kepler Mission scientist
Age: 49
Residence: Danville

In July, the Kepler Mission team announced the discovery of the most Earth-like planet yet. How’d you pull it off?
There’s a laundry list of things that astronomers can measure with current technology. Depending on the detection technique, you can measure the radius of the planet, or the orbital period—the time it takes for a planet to make one full orbit around its star. That information tells you the distance between the star and the planet. And if you know the temperature and luminosity of the central star, then given the distance of that star, you can estimate how much energy is received by the planet. In some cases you can measure the planet’s mass as well. If you have the mass and the radius, you can compute average density, which tells you if a planet is rocky, like Earth. And once you know that, you can gauge what conditions are on the surface.

And what might those conditions be on planet Kepler-452b?
If there are creatures on 452b, they are experiencing the same kind of sunshine that we experience. Kepler-452b is much larger than the Earth in radius, but it’s orbiting a normal G-type star, exactly like our sun—specifically, a G2, so its surface temperature is almost the same as our sun’s.

Is finding our doppelgänger the purpose of this mission?
Kepler was funded, built, and launched to do one very specific thing: determine the fraction of stars in our galaxy that host Earth-size, potentially habitable planets. So, really, what we’re doing is taking a census of sorts. We’re trying to infer something about demographics of planets in our galaxy.

And what are the census data?
We do have some preliminary numbers. It looks to me like somewhere between 15 and 25 percent of stars host potentially habitable Earth-size planets. In the next 20 to 30 years, we should be able to design an instrument capable of finding signatures of life.

What are those signatures?
What I’m talking about is an instrument that can capture light that has bounced off the planet from its central star and has passed through its atmosphere. When light passes through the atmosphere, a fingerprint of sorts is left on the light. We spread the light out in a spectrum, and what we look for in that rainbow are fingerprints telling us the atmosphere’s composition—we’re looking for chemical fingerprints of life; for example, oxygen.

Playing devil’s advocate, why do this when we have so many terrestrial needs? This satellite program cost some $600 million.
If you go to the website, you get some pretty good analogies: It’s estimated that in 2014, Americans spent $17.3 billion to celebrate Valentine’s Day. [NASA’s current budget is $17.5 billion.] Of every dollar spent by the government, NASA takes only a half penny. Compared to the Apollo era, that’s very tiny. Humanity needs a good dose of empathy. When we explore and understand the universe, we realize how connected we are. I think that goes a very long way toward helping the human condition.

Originally published in the September issue of
San Francisco

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