Exoplanets where life could develop as it did on Earth identified

Scientists have identified a group of exoplanets -- located outside our solar system -- where the same chemical conditions that may have led to life on Earth exist.

The chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star.

The study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could begin life on their orbiting planets in the same way it likely developed on Earth.

On Earth, the UV light powers a series of chemical reactions that produce the building blocks of life.

In the newly identified range of planets, the UV light from their host star is sufficient to allow the chemical reactions to take place, and that also lie within the habitable range where liquid water can exist on the planet's surface, the researchers said.

"This work allows us to narrow down the best places to search for life," said lead author Paul Rimmer, postdoctoral researcher at the University of Cambridge.

"It brings us just a little bit closer to addressing the question of whether we are alone in the universe," he added.

The team performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light.

While the experiment under the lights resulted in the necessary building blocks, the same experiment in the dark resulted in an inert compound which could not be used to form the building blocks of life.

The researchers then compared the light chemistry to the dark chemistry against the UV light of different stars.

They found that stars around the same temperature as our sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets.

Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step.

Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

--IANS

rt/bg