How to Find Aliens (Alien Plants, Too) by Probing a Planet’s Colors

For all our obsession with the possibility of intelligent alien life, the search for E.T. has so far been a letdown. What's a self-respecting alien-hunter to do?

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For all our obsession with the possibility of intelligent alien life, the search for E.T. has so far been a letdown. SETI, the organization famously scouring the heavens for alien life by scrutinizing radio signals for decades, has turned up nothing to speak of. What’s a self-respecting alien-hunter to do?

Start scrutinizing exoplanets more closely, for starters — specifically their colors, say scientists in a new paper titled “Colors of Extreme Exo-Earth Environments.”

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Let’s talk lingo: An “exoplanet” is just the fancy scientist way of referring to planets found orbiting stars outside our solar system. We’ve identified slightly more than 850 so far, with upwards of 18,000 additional candidates awaiting verification. And that’s just the start: NASA reports there may be hundreds of billions of exoplanets winging around our Milky Way galaxy alone.

Here’s another funny-sounding term: extremophiles, the word we use for microorganisms that can exist in humans might consider extreme environmental conditions — say in hydrothermal vents at the bottom of Earth’s oceans, or on the surface an exoplanet.

Scientists at the Max Planck Institute for Astronomy in Heidelberg, Germany and the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. are suggesting we start paying attention to these planets’ spectrographic fingerprints, using that as a way to narrow our search for alien life. The Earth, for instance, generates light at the near-infrared end of the electromagnetic spectrum because of the chlorophyll in plants. Looking for planets that exhibit a comparable “red edge” could indicate the presence of alien plant life.

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And since we’ve already detected rocky planets orbiting in the habitable zones of their stars, the scientists studied extreme Earth-based environments that harbor extremophiles to identify the “characteristic albedos” we might use to find comparably durable exoplanet-based alien microorganisms.

Little gray aliens with almond eyes or long-necked ones with glowing fingers it’s not, but at this point, just finding a bunch of alien microorganisms — to say nothing of something like an alien palm tree or rose bush — would be extraordinary enough.

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