  Considering subglacial liquid water, a significant extension of the classical
Habitable Zone is obtained. Elaborating on the model of Wandel (2023) it is
shown how an atmosphere and liquid water could survive on tidally locked
planets closely orbiting an M-dwarf host, extending the Habitable Zone boundary
inwards. In addition, subglacial liquid water could extend the Habitable Zone
beyond the outer boundary of the conservative Habitable Zone as well. These two
results enhance the circumstellar region with a potential for liquid water well
beyond the conservative boundaries of the classical Habitable Zone. It is
argued that the probable recent JWST detection of atmospheric water vapor on
the rocky Earth-sized exoplanet GJ 486 b, along with earlier detections of
water on other planets orbiting M-dwarf stars gives an empirical answer to the
much-argued question, of whether such planets can support liquid water, organic
chemistry and eventually life. It is shown how water on terrestrial planets
closely orbiting M-dwarf stars may sustain in a subglacial melting layer.
Finally, the model is applied to a few exoplanets demonstrating how water
detection may constrain their atmospheric properties.
