Colourful exoplanets may be first to show evidence of alien life

Colourful alien life may be the easiest to find. Credit: Don Johnston / Getty Images
Colourful alien life may be the easiest to find. Credit: Don Johnston / Getty Images

Exoplanets are now being discovered on a regular basis, including ones that may be potentially habitable. But when even the nearest ones are so far away compared to the planets in our own solar system, how could they be studied for possible signs of life? Is that even possible?

It is, and the answer might be similar to what we see when we look at Earth from space. Even if a planet’s surface can’t be imaged directly, the light it reflects can be analyzed – by doing so, scientists can examine the colours on the planet’s surface, according to a new study published in the journal Astrobiology.

On Earth, a large amount of near-infrared light is reflected off of the chlorophyll in plants. If an exoplanet also had green vegetation, it might also show a similar “red edge” in its light spectrum.

It is reasonable to think that more primitive types of life might be the first to be discovered, such as bacteria, lichen or algae on Earth, as they would likely be more common than more advanced forms of life. Such life forms would have their own unique colour patterns which could also be observed.

As of now, we are just on the technological edge of being able to make these kinds of observations; the next space and ground-based telescopes being designed for looking at exoplanets will be a big step forward in this area of research.

If such colours were detected on a potentially habitable exoplanet, it would be an exciting find, although possibly not definitive proof of life. Different kinds of planetary atmospheres could affect the light signature in unexpected ways, according to Nicolas Cowan of Northwestern University. As he notes, “Nature may be more creative than our little corner of the cosmos would have us believe.”

The paper and abstract are available here.

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Paul Scott Anderson is a freelance space writer with a life-long passion for space exploration and astronomy. He started his blog The Meridiani Journal in 2005, which is a chronicle of planetary exploration. He also publishes The Exoplanet Report e-paper. In 2011, he started writing about space on a freelance basis, and now also currently write for AmericaSpace and He has also written for Universe Today and SpaceFlight Insider, has been published in The Mars Quarterly and has done supplementary writing for the well-known iOS app Exoplanet for iPhone and iPad.


  1. I followed Brad’s work on this and have some emails and papers if anyone is interested I can dig them up….cambria at xtraDOTcoDOTnz

    He said they planned to follow up but it was some years ago and i’ve seen nothing recent. So logical to start with a local moon, right?

  2. There was an interesting blurb on the spectrum of Europa by Brad Dalton a few years ago, indications were that matches with earth organisms were discovered…but it quickly went silent. That ruddy brown-red staining is definitely not sulfate salts, which are colorless save ferrous which is pale green.

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