Superhabitable Super-Earths May Be Better Than The Real Thing

By Joelle Renstrom | Published

Kepler-62f, an exoplanet that is about 40% larger than Earth. It’s located about 1,200 light-years from our solar system in the constellation Lyra. Credit: NASA/Ames/JPL-Caltech
It’s hard to look at space-related news without seeing a mention of a newly discovered potentially habitable planet, or the latest calculation of just how many Earth-like planets may exist out there. All sorts of factors contribute to a planet’s habitability, including its location relative to its host star. “Goldilocks” planets are those that orbit close enough to a star to be warm enough to support life and liquid water, but aren’t too close to the sun to frizzle fry life forms. Most of the time, when astronomers, with the help of the Kepler telescope, find potentially habitable planets, they’re about the size and mass of Earth. But a new study suggests that planets bigger than Earth could actually be more conducive to life than Earth.

Scientists call potentially habitable planets double or triple the size of Earth “super-Earths” and have concluded that they may be “superhabitable.” In a paper published in Astrobiology, astronomers suggest that bigger might actually be better in the case of habitability because tectonic activity on larger planets takes longer to happen, which reduces the likelihood of frequent and sudden earthquakes and other disruptive or destructive events. The fewer and less frequent the tectonic shifts, the more stable the planet and the longer life has to get a foothold and start to flourish. Bigger planets also tend to have thicker atmosphere, which can help promote life-enhancing weather systems and shielding against radiation and solar flares.

The astronomers are specifically arguing against something called the Rare Earth hypothesis, which posits that life on Earth emerged from an unlikely, specific, and serendipitous set of conditions on Earth, and that life elsewhere in the universe would be an “unlikely phenomenon.” While the astronomers admit that “the occurrence of another truly Earth-like planet is trivially impossible,” they take issue with the idea that that Earth’s special set of characteristics make it any less likely for other planets to harbor life. In fact, they actually think that Earth may only be “marginally habitable,” and that many other planets or even moons may be more conducive to life. So rather than Earth being rare, it may be the case that life on Earth was unlikely.

The astronomers think that continuing to focus on identifying candidate planets makes sense, and that Alpha Centauri, the system nearest to our own (only four light-years away!) is the best place to start given that its age and radiation levels are both suggestive of the possibility of life — or, at least, don’t rule life out. Looks like those predictions for finding extra-terrestrials might not be so crazy after all.