Atmosphere and water retention of an Earth-like planet by stellar host mass after 6 Gyr of evolution. The top panel shows atmosphere loss, while the bottom panel shows surface water loss. The (darker) burgundy shaded area shows the range of possible effects of radioisotopes for a planet orbiting in the outer habitable zone, while the (lighter) orange shaded area indicates the same for the inner habitable zone. The green shaded area marked “HZ” shows atmosphere and water retention at all other locations in the habitable zone.