What is the primary determinant of whether a planet resides in the habitable zone of a planetary ...

Answer to q. 1

The distance from its star and hence the temperature of the planet's surface to allow for formation of liquid water for life to evolve in.

Answer to q. 2

The lifetime of a technological civilization

Answer to q. 3

Water ice at the poles, photographic evidence of past flowing and standing water, and the rover Opportunity found its landing site was once drenched with water.

Answer to q. 4

Europa has an icy surface below which there may be liquid water.

Answer to q. 5

Both assume we are nothing special, not in the center of anything, and without anything remarkable happening here that could not occur elsewhere.

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