Alien flora

Exotic extraterrestrial foliage has been a science fiction staple since Wells' described the invading red plants of Mars in 1898. While red plants are colorful, natch, they don't necessarily have any basis in biology. Fortunately for people who like bio-accuracy in their science fiction, NASA biometeorologist Nancy Kiang and colleagues have published an article that predicts the color of plant life on extrasolar planets based on the type of star the planet orbits and the predicted planetary atmosphere.

The plant color we see is determined by the wavelength of light reflected by their leaves. Typical green plants absorb photon-rich red light and high-energy blue light and reflect the unused green light. Light absorbing pigments such as chlorophyll capture the photons' energy, which is then used to convert carbon dioxide and water into sugar. Based on the current understanding of that process of photosynthesis in terrestrial plants and bacteria, the NASA-lead research team believes that plants can come in many colors - except bright blue.

The [email protected] article conveniently provides a star type - plant color guide:

HOTTER THAN THE SUN
Plants will mainly be white, green, yellow, orange or red.

LIKE THE SUN
Green, yellow, orange.

COOLER THAN THE SUN
Green, yellow, orange.

RED DWARF
Black, grey-white, purple, many other colours.

It looks like red is an unlikely color for plants growing in our solar system. But if the invaders were from a planet orbiting Sirius, that's another story.

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