The comparison of Earth and Kepler-452b. (File photo)

7. Closest “twin” to Earth is discovered; evidence of water having flowed on Mars is confirmed

On July 23, NASA announced a planet that was “the closest twin to Earth” ever discovered. The planet was named Kepler-452b. It is the smallest world discovered orbiting in the habitable zone of a star. On Sept. 28, data from a NASA spacecraft confirmed that they had found the first evidence of briny water flowing on the surface of Mars as recently as last summer, raising the possibility that the planet could support life.