Pseudo-Earths are out there. That’s the message of today’s exciting announcement that a planet about the same size as Earth lives in its star’s habitable zone—the temperate region around a star where liquid water might flow. “For me, the impact is to prove that such planets really do exist,” said David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, to Nature.
It’s an article of faith that the planets most likely to harbor life are the planets most like Earth. Our home is, after all, the only known place in the universe that gives life shelter. From our sample of size of one we peer out into the cosmos for places that might mirror back the essential features that make our planet so fertile.
Unfortunately, discovering distant planets is so difficult that we can only discern the barest information about any potential neighbor. In the case of Kepler-186f, the newly discovered Earth-like exoplanet, astronomers know its size (about 1.11 times the radius of Earth), the length of its year (130 Earth days), and how much solar radiation it receives (about 32 percent of what the Earth gets from the Sun). Other questions—what is it made of? does it have an atmosphere? how hot is its surface?—we can only answer indirectly, if at all. There’s no way to tell, in other words, if the surface of Kepler-186f supports swimmable temperatures between zero and 100 degrees Celsius.
But we can flip the question of habitability around. Instead of assuming that the most life-friendly planets are Earth-sized orbs circling a Sun-like star, we can ask what characteristics a planet might have if we were to build it from scratch with the express purpose of setting the stage for the genesis of life and evolutionary success. What simple beginnings would best brew life’s endless forms most beautiful?
The answer, it turns out, isn’t an exact copy of Earth. Astronomers have recently begun to ponder the possibility of a “superhabitable” planet—one that has all the life-giving features of Earth, but more so. What are the characteristic signatures of such a world? As the astronomers René Heller and John Armstrong describe in a recent paper, these planets will be slightly larger than Earth—up to about two or three times Earth’s radius. These chubby Earths would presumably have more magnetic shielding from solar radiation; greater tectonic activity, which means more volcanoes to belch carbon dioxide into the atmosphere; a thicker atmosphere, held in by the greater surface gravity, and simply more surface area for life to roam.
I'd go there in a heartbeat, IF it was quick and safe. ;-) To read more, click here.