MASSIVE: Life may be evolving beyond Earth, suggests a new research

Life may be evolving on rocky, Earth-like planets orbiting in habitable zone of some of our closest stars which are bombarded by high levels of riation, according to a study.

Proxima-b, only 4.24 light years away, receives 250 times more X-ray riation than Earth and could experience dely levels of ultraviolet (UV) riation on its surface, said researchers from Cornell University in US.

According to study, published in journal Monthly tices of Royal Astromical Society, life alrey has survived this kind of fierce riation on Earth.

All of life on Earth today evolved from creatures that thrived during an even greater UV riation assault than Proxima-b, and or nearby exoplanets, currently endure.

Earth of four billion years ago was a chaotic, irriated, hot mess. Yet in spite of this, life somehow gained a toehold and n expanded.

same thing could be happening at this very moment on some of nearest exoplanets, researchers said.

y modelled surface UV environments of four exoplanets closest to Earth that are potentially habitable: Proxima-b, TRAPPIST-1e, Ross-128b and LHS-1140b.

se planets orbit small red dwarf stars which, unlike our Sun, flare frequently, bathing ir planets in high-energy UV riation.

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While conditions prevail upon surface of planets orbiting se flaring stars, it is kwn that such flares are biologically damaging and can cause erosion in planetary atmospheres.

High levels of riation cause biological molecules like nucleic acids to mutate or even shut down.

researchers modelled various atmospheric compositions, from ones similar to present-day Earth to "eroded" and "axic" atmospheres -- those with very thin atmospheres that don't block UV riation well and those without protection of ozone, respectively.

models show that as atmospheres thin and ozone levels decrease, more high-energy UV riation reaches ground. researchers compared models to Earth's history, from nearly four billion years ago to today.

Although modelled planets receive higher UV riation than that emitted by our own Sun today, this is significantly lower than what Earth received 3.9 billion years ago.

"Given that early Earth was inhabited, we show that UV riation should t be a limiting factor for habitability of planets orbiting M stars," said researchers.

"Our closest neighbouring worlds remain intriguing targets for search for life beyond our solar system," y said.

To judge potential habitability of worlds with varying rates of riation influx, researchers assessed mortality rates at different UV wavelengths of extremophile Deicoccus riodurans, one of most riation-resistant organisms kwn.

t all wavelengths of UV riation are equally damaging to biological molecules, researchers said.

A dos of UV riation at 360 nametres would need to be three orders of magnitude higher than a dos of riation at 260 nametres to produce similar mortality rates in a population of this organism," y said.

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Many organisms on Earth employ survival strategies -- including protective pigments, biofluorescence, and living under soil, water or rock -- to cope with high levels of riation that could be imitated by life on or worlds, researchers te.

Subsurface life would be more difficult to find on distant planets without kind of atmospheric biosignatures telescopes can detect.