Light spectrum from the atmospheres of two Earth-like planets could provide evidence of life, writes Rowan Philp. Two planets as friendly to life as the Earth have been found. Now, Harvard astronomers have told the Mail & Guardian that confirming the existence of life out there is just a matter of time, using an ingenious trick with starlight.
Just Google "solar spectrum", and you will see what "sunshine" really looks like under the proverbial microscope. The pair of dark shadows you will see in the burnt-yellow section of its rainbow, reflecting its strong sodium content, is our Sun's unique calling card.
The initial question for Kaltenegger and other astrobiologists was this: What would happen if that same bolt of light also passed through the atmosphere of an alien planet as it passed in front of its star before reaching our telescopes? Answer: More rainbow shadow lines. If she can find spectral lines for oxygen and methane, which a parent star itself does not have, she will have made a discovery on the scale of Hubble or Galileo.
Roughly 1000 extrasolar planets have so far been confirmed, but the vast majority are way too big or too hot for life to have a chance.
Until recently, the "signatures for life" technique was of little use, as most extrasolar planets were found because of wobbles in the orbits of their parent stars, tugged by the planet's gravity.
Most that were found this way were many times bigger than Jupiter and stiflingly close to their stars. But the Kepler mission finds smaller, Earth-like planets by patiently waiting for one to pass across the face of a star, momentarily reducing its light.
Kepler's alignment of star, planet and Earth puts this approach in pole position to make the find.
John Grunsfeld, the associate administrator for Nasa's science missions, said: "The Kepler spacecraft has certainly turned out to be a rock star of science. The discovery of these rocky planets in the habitable zone brings us a bit closer to finding a place like home.
"It is only a matter of time before we know if the galaxy is home to a multitude of planets like Earth, or if we are a rarity."