Life Could Be Evolving Right Now on Nearest Exoplanets

Rocky, Earth-like planets orbiting our closest stars could host life, according to a new study that raises the excitement about exoplanets.

When rocky, Earth-like planets were discovered orbiting in the habitable zone of some of our closest stars, excitement skyrocketed - until hopes for life were dashed by the high levels of radiation bombarding those worlds.

Proxima-b, only 4.24 light-years away, receives 250 times more X-ray radiation than Earth and could experience deadly levels of ultraviolet radiation on its surface. How could life survive such a bombardment? Cornell University astronomers say that life already has survived this kind of fierce radiation, and they have proof: you.

Lisa Kaltenegger and Jack O'Malley-James make their case in a new paper, published in Monthly Notices of the Royal Astronomical Society. Kaltenegger is associate professor of astronomy and director of Cornell's Carl Sagan Institute, at which O'Malley-James is a research associate.

All of life on Earth today evolved from creatures that thrived during an even greater UV radiation assault than Proxima-b, and other nearby exoplanets, currently endure. The Earth of 4 billion years ago was a chaotic, irradiated, hot mess. Yet in spite of this, life somehow gained a toehold and then expanded.

The same thing could be happening at this very moment on some of the nearest exoplanets, according to Kaltenegger and O'Malley-James. The researchers modeled the surface UV environments of the four exoplanets closest to Earth that are potentially habitable: Proxima-b, TRAPPIST-1e, Ross-128b and LHS-1140b.

These planets orbit small red dwarf stars which, unlike our Sun, flare frequently, bathing their planets in high-energy UV radiation. While it is unknown exactly what conditions prevail upon the surface of the planets orbiting these flaring stars, it is known that such flares are biologically damaging and can cause erosion in planetary atmospheres. High levels of radiation cause biological molecules like nucleic acids to mutate or even shut down.

O'Malley-James and Kaltenegger modeled various atmospheric compositions, from ones similar to present-day Earth to "eroded" and "anoxic" atmospheres - those with very thin atmospheres that don't block UV radiation well and those without the protection of ozone, respectively. The models show that as atmospheres thin and ozone levels decrease, more high-energy UV radiation reaches the ground. The researchers compared the models to Earth's history, from nearly 4 billion years ago to today.

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

"Given that the early Earth was inhabited," the researchers wrote, "we show that UV radiation should not be a limiting factor for the habitability of planets orbiting M stars. Our closest neighboring worlds remain intriguing targets for the search for life beyond our solar system."

Research Report: "Lessons from Early Earth: UV Surface Radiation Should Not Limit the Habitability of Active M Star Systems," Jack T. O'Malley-James and Lisa Kaltenegger, 2019 April 9, Monthly Notices of the Royal Astronomical Society

Related Links
Cornell University
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth

Tweet

Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Monthly Supporter
$5+ Billed Monthly

paypal only

SpaceDaily Contributor
$5 Billed Once

credit card or paypal

Building blocks of DNA and RNA could have appeared together before life began on Earth
La Jolla CA (SPX) Apr 03, 2019
Scientists for the first time have found strong evidence that RNA and DNA could have arisen from the same set of precursor molecules even before life evolved on Earth about four billion years ago. The discovery, published April 1 in Nature Chemistry, suggests that the first living things on Earth may have used both RNA and DNA, as all cell-based life forms do now. In contrast, the prevailing scientific view - the "RNA World" hypothesis - is that early life forms were based purely on RNA, and only ... read more