'Probably Not Alone': NASA's Kepler Telescope Reveals More Rocky Planets Like Earth Than Previously Estimated

Norman Byrd

Data gleaned from observations taken from the Kepler Space Telescope indicates that there are far more rocky planets like Earth than astronomers previously estimated. And with more exoplanets that could have similar general characteristics to our planet, the only known harbor of living organisms that we know about, the more likely we are to find alien life somewhere else in the expansive universe, scientists are saying.

At the Kepler Science Conference held at NASA's Ames Research Center in Silicon Valley, California, in mid-June, scientists met to present new data and update ongoing research from the two missions of the Kepler Space Telescope. As Space reported, one find among the gathered data stood out from the rest: Rocky exoplanets (similar to Earth) are likely far more common than scientists had previously estimated. This "enhances," Space pointed out, "the prospects for extraterrestrial life in nearby solar systems."

The number of exoplanets detected by Kepler, which has been focused on a field of 200,000 stars in the Cygnus constellation, totaled 4,034 candidates. Of those, 50 are Earth-sized and within their parent stars' habitable zone, an area distant from the parent star where liquid water is most likely to be present. Moreover, of the 50, six confirmed rocky exoplanets circle G-dwarf stars, the same classification as the Sun.

Before the Kepler Space Telescope's K2 mission, a "second life" mission charged with the detection of exoplanets, exoplanets detected by astronomers were mostly Jupiter and Neptune-sized worlds.

"Are we alone?" said Mario Perez, Kepler program scientist in the Astrophysics Division of NASA's Science Mission Directorate. "Kepler says we are probably not alone."

Of course, the existence of more rocky exoplanets is no guarantee that they will be cradles of life, either. Numerous factors, all currently unknown variables at this stage, could relegate even the most advantageously positioned planets to lifelessness.

The current record-holder for rocky exoplanets is held by the TRAPPIST-1 system, which has seven Earth-sized worlds. All orbit relatively closer to their red dwarf parent star with three circling within the habitable zone. Although the theory of panspermia has gotten much play concerning the exoplanets' proximity to each other, the fate of life among the seven may be tied to the parent star and the propensity for red dwarfs to flare and shower their planets with ultraviolet radiation, a known atmosphere stripper.

Still, Courtney Dressing, a CalTech astronomer, has run model simulations and found that exoplanets orbiting so close to their parent stars, even though they might be tidally locked (one side getting all the star's light, the other side bathed in darkness), could find atmospheres surviving the ultraviolet bombardment if strong currents of air evened out the planets' temperatures.

"There's a chance you could have a bunch of civilizations where maybe all the astronomers live on one side of the planet and everyone else enjoys the sunny, beach-y side close to the star," she said.

Dressing points out that alien life might still be discovered underground or underwater.

"Regardless of whether any of these newly detected planet candidates are inhabited, the fact that Kepler has discovered 50 potentially habitable planets and planet candidates implies that such worlds are frequent," wrote Dressing in an email to Space.

Even though the chances of finding alien life seems to be increasing, given recent discoveries of life-forming substances and indicators, the official position of NASA is that no definitive proof has thus far been presented that confirms that life exists anywhere other than on Earth. The hope is that, with technological and astronomical advances (not to mention further exploration of potential life-harboring worlds within our own Solar System), the vast array of planets being discovered will one day lead to evidence that Earth is not alone.

[Featured Image by By NASA/JPL-Caltech/Wendy Stenzel (Public domain)/Wikimedia Commons]