Can a planet have blue plants?

Plants on Earth-like planets orbiting stars somewhat brighter than the Sun might look yellow or orange (Illustration: Doug Cummings/Caltech)

The greenery on other planets may not be green. Astrobiologists say plants on Earth-sized planets orbiting stars somewhat brighter than the Sun may look yellow or orange, while those on planets orbiting stars much fainter than the Sun might look black.

Vegetation colour matters to astrobiologists because they want to know what to look for as a sign of life on planets outside the solar system. Terrestrial photosynthesis depends mostly on red light, the most abundant wavelength reaching the Earth’s surface, and blue light, the most energetic. Plants also absorb green light, but not as strongly, so leaves look green to the eye.

Extraterrestrial plants will look different because they have evolved their own pigments based on the colours of light reaching their surfaces, says Nancy Kiang of the NASA Goddard Institute for Space Sciences in New York, US.


To determine the best colours for photosynthesis on other planets, Kiang worked with NASA’s Virtual Planetary Laboratory at Caltech to determine the light reaching the surfaces of Earth-sized worlds orbiting their host stars at distances where liquid water – and therefore life – could exist. The results depended on the star’s brightness and the planet’s atmosphere.

Autumn colours

Brighter stars emit more blue and ultraviolet light than the Sun. An oxygen atmosphere would form ozone that blocks the ultraviolet but transmits more blue light to the ground than on the Earth. In response, life would evolve a type of photosynthesis that strongly absorbs blue light, and probably green as well. Kiang says yellow, orange, and red would likely be reflected, so the foliage would wear bright autumn colours all year round.

A star slightly dimmer than the Sun would deliver a solar-like spectrum to the surface of a terrestrial planet, so its foliage would look much like the Earth’s.

But plants would be different on planets orbiting small M-type stars, or red dwarfs, which are between 10% and 50% the mass of the Sun. Red dwarfs, which comprise 85% of the galaxy’s stars, emit strongly at invisible infrared wavelengths but produce little blue light.

“They’ll definitely be absorbing in the infrared,” unlike terrestrial plants, Kiang told New Scientist. Because they would benefit by absorbing visible light, she says they might look black, although she admits that any colour might be possible. Whatever their colour, the plants would likely look dark to humans because little visible light would reach the ground.

Floating and sinking

Photosynthesis might not draw enough energy from infrared light to produce the oxygen needed to block dangerous ultraviolet light from the dwarfs.

But if there were at least 9 metres of water on the planet, mats of algae would be protected from the planet-scalding ultraviolet flares produced by young red dwarf stars, says Victoria Meadows of Caltech, principal investigator at the Virtual Planetary Laboratory.

She envisions a bizarre world where microbial mats float near the surface for efficient photosynthesis when the star is calm, then sink to a safe depth when a flare hits.

Life could spread further when the stars pass their flare stage, she told New Scientist: “M stars don’t produce a lot of ultraviolet once they quiet down, so you don’t need an oxygen layer to shield [life] from the ultraviolet.”

Journal reference: Astrobiology (vol 7, p 252)

More on these topics:

  • astrobiology


Trending Latest Video Free

  1. Why the laws of physics don't actually exist
  2. LIGO may be able to detect alien warp drives using gravitational waves
  3. JWST has broken the record for most distant galaxy ever confirmed
  4. Experimental CRISPR technique has promise against aggressive leukaemia
  5. Drug clears sleeping sickness parasite from the body in clinical trial

  1. NASA’s Artemis I mission has ended as Orion splashed down on Earth
  2. Learn the secrets of poinsettias to help them thrive
  3. Hung over: What science says about why you feel so rough
  4. Experimental CRISPR technique has promise against aggressive leukaemia
  5. How Birds Evolve review: In-depth and passionate

  1. Livestream: Watch Hawaii’s Mauna Loa volcano erupting
  2. Lee Berger: Rewriting human history
  3. Flying squirrels carve nuts to store them securely in tree branches
  4. Artemis astronauts prepare for future moon missions in Arizona desert
  5. Liza Bec: The composer living with music-triggered epilepsy

  1. NASA’s Artemis I mission has ended as Orion splashed down on Earth
  2. Hung over: What science says about why you feel so rough
  3. Experimental CRISPR technique has promise against aggressive leukaemia
  4. Farting 101: The questions you're too embarrassed to ask
  5. JWST has broken the record for most distant galaxy ever confirmed

Can a planet have blue plants?

  • Subscribe
  • View in the app
  • Buy In Print



Can a planet have blue plants?

Bacteria could survive just under Mars's surface for 280 million years

When bacteria are dried and frozen, as they most likely would be just under the surface of Mars, they can survive the intense radiation that hits the Red Planet for hundreds of millions of years


Can a planet have blue plants?

Shards of pure ice might snow upwards beneath the ice shell of Europa

The moons Europa and Enceladus probably have global oceans buried beneath their frozen shells, and those seas may be home to a strange kind of ice called frazil ice


Can a planet have blue plants?

Meteorites on Mars may preserve evidence of ancient alien life

When meteorites land on Earth, microbes soon begin colonising them. If Mars once had life, microbes might have colonised meteorites there too


Can a planet have blue plants?

Perseverance rover measures speed of sound on Mars for the first time

Using a laser to strike rocks and a built-in microphone, NASA’s Perseverance rover has measured changes in the speed of sound on Mars due to temperature affecting the atmosphere

Can plants be different colors on planets?

Each planet will have different dominant colors for photosynthesis, based on the planet's atmosphere where the most light reaches the planet's surface.

Can plants blue?

Although blue flowers are rare in plants, almost no plant has blue leaves – except a handful of plants found on the floor of tropical rainforests. The main reason for this has to do with the physics of light. Pigments appear the colour of the light they don't absorb, but instead reflect.

What Colour would plants be if the sun was blue?

Around stars hotter and bluer than our sun, plants would tend to absorb blue light and could look green to yellow to red.

What color would plants be on Mars?

Mars has lots of iron dust which makes it look reddish. Iron compounds tend to have reddish-brown color so you may expect Martian plants to have a dun tint.