Life on other planets may be completely different than previously thought

NASA has already spotted several rocky, Earth-like exoplanets in the cosmos. But unlike our green and blue planets, many of these worlds may have purple life flourishing. Provided, of course, that there is life out there.

It is possible that living things elsewhere resemble the colors of trees, algae and other plants that dominate Earth’s nature.

The green life here absorbs the sun’s rays to produce energy through photosynthesis, and the green-colored compound chlorophyll happens to aid in this highly successful process, Space.com reports.

According to new research by astro- and microbiologists, life elsewhere probably gets its energy from a different type of sunlight, using compounds that contain purple pigments instead of green.

This is not an idea that came out of thin air at all, because here on Earth there are also purple-colored microbes. However, at home, in our current oxygen-rich environment, most ecosystems are green.

“But this is not necessarily the case on other planets,” Lígia Fonseca Coelho, a microbiologist at Cornell University’s Carl Sagan Institute and leader of the research, told Mashable.

The research was recently published by Monthly Notices of the Royal Astronomical Society in a scientific journal.

One of the main goals was to show observatories how to look for telltale signs of purple life when observing distant exoplanets.

Upcoming extremely powerful telescopes, such as the Extremely Large Telescope in the mountains of Chile and the Habitable Worlds Observatory, which would orbit in space, will study the atmospheres of such distant worlds to determine their composition and habitability.

The scientists extracted more than 20 purple bacteria from different ecosystems, such as lakes and marshes in Massachusetts and New York, and measured their vibrant pigments and how they emit light.

They then simulated the chemical fingerprints that would be visible in the reflected light of an alien planet, and found that these purple bacteria generate vivid, identifiable signals.

Coelho emphasized that “we should not only look at the green. Let’s look for purple too. We end up overlooking a sign of life because we were biased.”

Purple life may not exist, but it may be more common than we think

Most of the stars in our Milky Way are small red stars, the so-called red dwarf stars. The closest star to Earth is one of them, Proxima Centauri. These stars are only a fraction of the size of the Sun and are considered among the coldest.

Accordingly, most of the light emitted by red dwarfs is of a lower energy (infrared or red light wave), so nearby organisms probably have to use this infrared light, i.e. invisible to us, to feed their cells.

“If there is life on the planet, it will use this infrared energy instead,” explained Coelho. What is important to know is that purple bacteria on Earth feel good even in such a lower energy environment.

On a planet where green microbes and organisms couldn’t survive or weren’t the best fit to survive, purple pigmented alien life could outcompete them and take over.

It’s even possible that such purple bacteria once flourished on early Earth. They see a chance for this because oxygen only existed for about half of our planet’s 4.5 billion year lifespan.

There was a time when the world was covered by non-green, oxygen-emitting and photosynthesizing plants. Different bacteria may have once flourished on our planet, which obtained energy from different chemical processes.

“Perhaps the Earth was once covered in purple.”

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