Question: Okay, seriously? Purple plants? That sounds like something from a fantasy story. 

Believe it or not, it’s true. At least according to scientists at NASA’s Jet Propulsion Laboratory who study extraterrestrial life and try to guess what it might be like.

Did you ever notice how, not counting flowers or budding plants like food, everything on Earth is green? Take a moment and think about that. Why are they all green? To answer that, let’s look at plant physiology for a moment.

Plants get energy from the sun through a process called photosynthesis. Chlorophyll in the plants converts the sun’s energy into useable compounds, like sugars.

Image Credit: NASA

Our sun, Sol, is classified as a “Yellow” star (G2V to be exact). This doesn’t mean that it’s literally yellow colored, but that it gives off light in the yellow EM bands. All stars emit different bands of EM energy from the star where some bands are stronger than others.

EM Bands found in Stars. Image Credit: NASA

Once that light is filtered through the Earth’s atmosphere, some of the light is blocked or changed until a specific band remains. In order to capture as much of the light reaching the ground as possible the plants use Chlorophyll in the photosynthesis process. This is what gives the plants the green color.

If the Earth, or another planet with a similar atmosphere, were orbiting around a star that emitted a different EM band of light, then the atmosphere would filter out different wavelengths and the plants would be different colors. Around a dimmer star, like a K-Type or an M-Type, the plants would be darker, like this…

Image Credit: Caltech/JPL/NASA

 

And that’s just for plants around a single star! You don’t want to know how complicated it gets for plants around binary stars or multiples.

If you’d like to read more about this discovery I would recommend the following links:

NASA/GSFC press release
Spitzer news release
Nancy Y. Klang, Scientific American, April 2008
Astrobiology
Kiang et al, 2007a
Kiang et al, 2007b