Scientists studying exoplanet biosignatures suggest that vegetation on other worlds may appear purple rather than green [1].

This theory alters how astronomers search for signs of life beyond the solar system. Because the color of a planet's surface can indicate the type of biological processes occurring there, understanding potential pigment variations helps refine the search for alien life.

On Earth, plants are green because they use chlorophyll to absorb blue and red light from the sun. However, the light emitted by stars varies significantly across the universe [1]. Different stellar spectra could favor the evolution of photosynthetic pigments that reflect different wavelengths of light.

If a star emits light in a spectrum different from the sun, plants on those orbiting exoplanets might evolve to absorb different energies to survive [1]. This biological adaptation could result in foliage that appears purple to a human observer, a shift driven by the necessity of maximizing energy absorption from the local star.

Researchers focus on these biosignatures to identify habitable worlds. By analyzing the light reflecting off a distant planet, scientists can determine the composition of its atmosphere and surface [1]. The presence of specific colors could signal the existence of photosynthetic organisms that differ fundamentally from those on Earth.

While these findings remain speculative, they provide a framework for interpreting data from next-generation telescopes. Identifying the specific pigments used by alien flora would offer a direct window into the chemistry of an alien world [1].

“Alien plants may be purple rather than green.”

The shift from green to purple in theoretical alien botany highlights that 'life as we know it' is limited by Earth's specific solar environment. By expanding the parameters of what a biosignature looks like, scientists are less likely to overlook life that evolves under different stellar conditions, moving the search for extraterrestrial life beyond a carbon-copy of Earth's biology.