Another Earth 2.0? Not So Fast

The number of confirmed exoplanets now exceeds 3000, with an additional nearly 5000 exoplanet candidates awaiting confirmation in the NASA Exoplanet Archive ( 2016 ). Nearly weekly we hear about the detection of a new exoplanet similar in mass to Earth and located in the so-called habitable zone around its host star. The excitement is understandable given our desire to find a second Earth. However, the excitement should not lead to an over-interpretation of the findings, because the claim can only be to have some crude similarity to Earth based on a few selected geophysical parameters. Only a very small fraction of these planets will actually be Earth-like. Earth-like would imply multiple environmental habitats and presence of a sizable biosphere and complex ecosystems, without which Earth, as we experience it, would not exist. Thus, it should be clearly communicated to the public that we are probably still many years away from having the technological capability to detect an Earth-like planet or Earth 2.0 with adequate certainty. Key Words: Habitable zone-Second Earth-Habitable planet-Habitability-Life. Astrobiology 16, 817-821.