A new age of interstellar exploration has begun; NASA’s Kepler Mission successfully launched on Friday night. Now moving into its permanent operating position in Earth’s shadow, Kepler possesses the technological capacity to detect Earth-sized worlds orbiting other stars and examine such planets for the chemical traces of life.
Kepler is slated to examine on the order of 100,000 stars in the Galaxy and chart their planets as best it can. Kepler will closely watch those stars, and where planets are found their size, mass, orbital characteristics, temperature and age can be tallied. Kepler will look at Hot Jupiters, Super-Earths, Ice Giants, Warm Neptunes, Chilly Venuses, Mega-Mercurys, Dyson Spheres, Star-Feeding Von Neumann Hives and whatever the hell else exists out there… including rocky planets of about Earth’s size and mass.
Kepler has one instrument: a gigantic, lidless eye designed to stare at one small region of the sky continuously for three and a half years. There is ample room for many more Keplers… this one will look at only a single 12-degree diameter patch of sky, and there’s plenty more sky out there. Kepler will accumulate light from its assigned patch of sky over the entire life of its mission, slowly building a detailed, high-resolution picture of everything within its field and depth of view.
Kepler’s eye can see visible to near-infrared colors, meaning it can detect the temperatures of stars and worlds, and it can tell – when conditions are right – if certain chemical compounds are abundant in the atmospheres of extrasolar planets. Kepler can detect traces of carbon dioxide, methane, ozone, molecular oxygen, water vapor, and other compounds.
To Kepler’s eye, what would another Earth look like? It would probably look like a clear signal of O2 and H2O in the atmosphere of a small, rocky planet with a surface temperature capable of supporting liquid water. Kepler will be able to find things like that.
The smaller the planet, the smaller its signal, and the more staring Kepler will need to do. Big planets are easy to detect right away, because their gravitational effects are larger and their shadows are fatter. Before Kepler finds any Earths, it will find a great many Jupiters, Saturns, Uranuses, and Neptunes. That’s fine, because as it stares it will accumulate more and more light, until eventually its view clarifies to where it can pick out little Class M planets. That will take time, but it will happen. At some point, a few months to a couple of years from now, it is possible – reasonably likely, perhaps – that NASA’s Kepler device will deliver humanity its first plausible evidence of life beyond our solar system. That evidence will arrive as lines of color, redacted from faraway sunlight passing through the air of an alien biosphere.