A Dynamic Scheme to Assess Habitability of Exoplanets

In the next few years, the number of catalogued exoplanets will be counted in the thousands and with it the need will arise to prioritize them in regard to habitability and the potential presence of life. Here, we suggest a first attempt of a dynamic scheme for classification based on our current understanding of parameters that are consistent and beneficial for the presence of life. These parameters include the presence of (1) a terrestrial planet or moon, which (2) is endowed with a significant atmosphere; the presence of (3) a magnetic field enveloping the exoplanet; (4) internal differentiation and plate tectonics; (5) detectable surface liquids, preferably water, on the surface of the planetary body; and (6) the detection of geoindicators; and (7) bioindicators. We propose to calculate a habitability index (HI) based on these parameters, but realize the assumptions that go into this value and the very bias introduced by the limitations of the detection methods. However, in order to account for the assumptions and limitations of this method, the HI index is an open scheme that can be updated as technology and our knowledge about habitable planets advances.