A Methane Extension to the Classical Habitable Zone
"... We use a single column radiative-convective climate model to assess the greenhouse effect of CH4 (10 to about 100,000 ppm) on the classical habitable zone (N2-CO2-H2O) for main-sequence stars with stellar temperatures between 2,600 to 10,000 K (about A3 to M8). ... We show that 10% CH4 can increase the width of the classical HZ of the hottest stars (TEFF = 10,000 K) by over 20%. In contrast, the CH4 anti-greenhouse can shrink the HZ for the coolest stars (TEFF = 2,600 K) by a similar percentage. ... We parameterize the limits of this N2-CO2-H2O-CH4 habitable zone and discuss implications in the search for extraterrestrial life."