Excitement skyrocketed with the discovery of Earth-like, rocky planets when they were discovered orbiting the habitable zone of some of our closest stars. The enthusiasm was short-lived since there was a high degree of radiation shelling those worlds.
With only 4.24 light years away, Proxima-b gets 250 times more X-ray radiation than Earth with the potential of experiencing deadly levels of ultraviolet radiation on its surface. The question is how life could survive such a bombardment. According to the astronomers from Cornell University, life has already survived such fierce radiation like this, and their proof of that is you!
In a new paper published in the Monthly Notices of the Royal Astronomical Society, Jack O'Malley and Lisa Kaltenegger made this case.
In this present day, life on Earth evolved from creatures that thrived all through an evergreen UV radiation assault than Proxima-b, and another close by exoplanets, currently endure. Four billion years ago the state of Earth was irradiated, messy, and chaotic. And in spite of this condition, life still gained a toehold and then expansion.
Kaltenegger and O'Malley-James noted that at this very moment on some of the closest exoplanets, the same thing could be happening. They modeled the UV surface environments of the four exoplanets near to Earth that are potentially habitable namely, TRAPPIST-1e, Proxima-b, Ross-128b, and LHS-1140b.
The four planets orbit small red dwarf stars which, unlike the sun, frequently flare, bathing their planets in high-energy UV radiation. Though it is hard to specify the kind of condition prevailing upon the surface of the planet orbiting these flaring stars, it is also not known that such flares are damaging biologically and tend to trigger erosion in the planetary atmosphere. With high levels of radiation, there will be a cause for biological molecules like nucleic acids to mutate or even shut down.
Kaltenegger and O'Malley-James took their model on various atmospheric compositions, ranging from the ones similar to present-day Earth to "anoxic" and "eroded" atmospheres, the ones with thin atmospheres that further UV radiation well and those without the protection of ozone, in that order.
Their model also reveals more high-energy UV radiation reaching the ground as the atmosphere thin and ozone levels decrease. Then, the researchers made a comparison of the models to the history of the Earth from nearly 4 billion years ago to today.
While this analysis is significantly lower than what Earth received 3.9 billion years ago, the model planets receive higher radiation than that emitted by our sun today.
The researcher noted that even when the early Earth was inhabited, they were able to reveal that UV radiation may not be a limiting factor for the habitability of planets orbiting M stars. They believe that beyond our solar system, our closest neighboring worlds remain attractive targets for the search for life.
