Extraterrestrial life could be purple

The life of the extraterrestrials could be purple.

This is the conclusion of a new research paper that suggests that the first life on Earth could have had a lavender hue. In the International Journal of Astrobiology, microbiologist Shiladitya DasSarma of the University of Maryland School of Medicine and postdoctoral researcher Edward Schwieterman of the University of California at Riverside say that before that green plants harness the energy of the sun, tiny purple organisms figured a way to do the same thing.

Extraterrestrial life could flourish in the same way, said DasSarma.

"Astronomers have recently discovered thousands of new extrasolar planets and are developing the ability to see surface biosignatures" in the light of these planets, he told Live Science. There are already ways to detect green living from space, he said, but scientists may also have to start looking for purple. [7 Wild Theories on the Origin of Life]

Purple Earth

The idea that the primitive Earth was purple is not new, DasSarma and his colleagues advanced the theory in 2007. The thought is this: photosynthesizer plants and algae use chlorophyll to absorb the water. Sun energy, but not the green light. It's strange, because the green light is rich in energy. According to DasSarma and his colleagues, something else was already using this part of the spectrum when chlorophyll photosynthesizers evolved.

This "something else" would be simple organisms that capture solar energy with a molecule called retinal. Retinal pigments absorb green light better. They are not as effective as chlorophylls in capturing solar energy, but they are simpler, the researchers wrote in their new article published Oct. 11.

Retinal light collection is still widespread among bacteria and unicellular organisms called Archaea. These purple organisms have been found everywhere from oceans to leaf surfaces to the dry Antarctic valley, Schwieterman told Live Science. Retinal pigments are also found in the visual system of more complex animals. The appearance of pigments in many living organisms suggests that they may have evolved very early, in ancestors common to many branches of the tree of life, the researchers wrote. There is even evidence that modern salt-loving, pigmented purple organisms, called halophiles, could be linked to the oldest life on Earth, which has flourished around sources of methane in the ocean, Schwieterman said. .

Purple aliens

It does not matter that the first life on Earth is purple, it is clear that the life of lavender is perfect for some organisms, discuss Schwieterman and DasSarma in their new article. This means that extraterrestrial life could use the same strategy. And if extraterrestrial life uses retinal pigments to capture energy, astrobiologists will find them only by searching for particular light signatures, they wrote.

According to Schwieterman, chlorophyll mainly absorbs red and blue light. But the spectrum reflected by a planet covered with plants displays what astrobiologists call a "red edge of vegetation". This "red edge" is a sudden change in light reflection in the near infrared region, where plants suddenly stop absorbing red wavelengths and begin to reflect them.

Retina-based photosynthesizers, on the other hand, have a "green edge," said Schwieterman. They absorb light down to the green part of the spectrum, and then begin to think longer wavelengths.

Astrobiologists have long been intrigued by the possibility of detecting extraterrestrial life by detecting the "red edge," said Schwieterman, but they might also be led to consider looking for the "green edge".

"If these organisms were present at a sufficient density on an exoplanet, these reflective properties would be printed on the spectrum of reflected light from this planet," he said.

Originally published on Science live.