On Earth we find that life can flourish in environments between sub-freezing (0^o C) and hot springs (120^o C). At what distances from the Sun can this temperature range be maintained? The answer depends on assumptions about the planet's atmosphere.

If we moved Earth's orbit inwards, then the increased solar heating would cause evaporation of the oceans (along with its CO₂), increased Greenhouse Effect heating, eventual dissociation of water vapor in the atmosphere, and, ultimately, a runaway Greenhouse Effect (with a CO₂ atmosphere) - just like Venus.

On the other hand, if we moved Earth's orbit outwards, the polar caps would increase (eventually covering the whole world), the icy surface would better reflect sunlight (and further cool Earth), and even CO₂ in the atmosphere would eventually condense into clouds (reflecting sunlight). Mars is at the edge of such a deep-freeze zone (recall evidence of liquid water on the surface in the distant past).