The language of exoplanet ranking metrics needs to change (on the nature astronomy)
Elizabeth Tasker, Joshua Tan, Kevin Heng, Stephen Kane, David Spiegel & the ELSI Origins Network Planetary Diversity Workshop
We have found many Earth-sized worlds but we have no way of determining if their surfaces are Earth-like. This makes it impossible to quantitatively compare habitability, and pretending we can risks damaging the field.
See more at: http://www.nature.com/articles/s41550-017-0042