Broadening Habitability

MIT astronomer Sara Seager argues we shouldn't get too focused on finding nearly duplicate Earths when searching for alien life.  She says life could exist outside of a star's habitability zone given the right local environment.  Enough greenhouse gases in a planetary atmosphere, for example, could maintain a surface temperature warm enough to support life even if the planet orbited well beyond that star's calculated habitability zone.  She counsels scientists to keep an open mind on where life might be found.

Indeed, in our own Solar System, two of the stronger possibilities for alien life are Jupiter's moon Europa and Saturn's moon Enceladus, both of which are well outside the Sun's putative habitability zone, which extends not far beyond Mars.