Alien Life Could Look Different Than We Expect

Alien life may not have the familiar green color we associate with plant life on Earth.

Quick Facts

• New research from Cornell University challenges the idea of green alien planets.
• Purple bacteria, thriving in various conditions, could dominate on different worlds.
• Understanding the colors of extraterrestrial life is crucial for identifying signs of life on other planets.

If you were asked to imagine an alien planet, it would be reasonable to imagine a green earth-like rock orbiting somewhere in a distant solar system. But according to new research from Cornell University, we might be getting this color palette all wrong.

On Earth, plants get their green color from **chlorophyll** pigments in their leaves. But what if the major photosynthesizing life forms on other planets used a different form of energy?

“**Purple bacteria** can thrive under a wide range of conditions, making it one of the primary contenders for life that could dominate a variety of worlds,” said Lígia Fonseca Coelho, a postdoctoral associate at Cornell University’s Carl Sagan Institute.

In their study, published in the journal Monthly Notices of the Royal Astronomical Society, the researchers created models of numerous Earth-like planets with varying conditions and simulated how different types of purple bacteria might survive on these planets, and what color signatures they would produce under each set of conditions.