The life supporting zone of Kepler-22b and the Kepler planetary candidates: KOI268.01, KOI701.03, KOI854.01 and KOI1026.01

Abstract

The concept of the life supporting zone is a generalization of the concept of the habitable zone (and therefore for water based life, i.e. life-as-we-know-it) to other solvents (and to life-as-we-do-not-know-it). We present an estimate of life supporting zones of Kepler-22b and the Kepler planetary candidates KOI268.01, KOI701.03, KOI854.01 and KOI1026.01. The life supporting zone envelopes in this study the water, sulfuric acid and water/ammonia mixture habitable zones. Planetary surface temperatures were computed with a radiative convective model for “Venus-like” and “Earth-like” atmospheric scenarios including clouds. For Kepler-22b an Earth-like planet and an ocean planet (50wt% H2O) scenario are investigated. Restrictions on stellar and planetary input parameters are derived from the model simulations. The input parameters with the largest influence on planetary surface temperature are the stellar flux, the planets' surface albedo, the considered atmospheric scenario and cloud properties. Water and thick H2SO4-clouds lead to lower surface temperatures for small values of surface albedos and higher temperatures for higher albedos. For thin H2SO4-clouds the cooling effect dominates. All planet(ary candidate)s investigated are likely to lie in the life supporting zone. Kepler-22b and KOI701.03 are likely to lie in the water habitable zone.