Earth vs. Kepler-Who would want to go there?
All the known potentially habitable exoplanets so far are superterran worlds (aka super-Earths) somewhat larger than Earth. The potential of life of these worlds is difficult to relate to Earth since there are no planets in the Solar System of comparable size and we know very little of them. Now a team of scientists led by Elisa V. Quintana from the SETI Institute and NASA Ames report the discovery of Kepler-186f, the first terran world (Earth-size) in the habitable zone of a star.
Kepler-186f has a similar size to Earth and it is most likely a rocky world. It orbits the M-dwarf star Kepler-186 along with four other inner planets, which are as old as the Solar System (>4 Gyr), in the constellation Cygnus 500 light years away. Kepler-186f receives less stellar flux (~32%) than presently does Mars (~43%). It could have a temperate climate if it has an atmosphere much denser than Earth. Even Earth probably experienced at least one episode of global glaciation with just a slightly lower stellar flux than today, 650 million years ago. However, early Mars had running surface liquid water with a similar stellar flux as Kepler-186f.