[Carl Vehse]

Some of those habitability factors include suitable axis rotation rate; appropriate tilt of planet axis for seasons; protection from cosmic radiation by a sufficient magnetic field produced by a planet's molten core; sufficient recycling of crustal material by planetary plate tectonics; suburban galaxy location providing sufficient actinide radioisotopes for core decay heat; suitably sized moon to create appropriate-sized tides; giant outer gas planets to sweep up potentially dangerous loose asteroids and comets; sufficient distance from recent supernovas.

And from recent announcements, another parameter may be the effect of nearby planets in creating planetary climate change by periodic orbital variations caused by small chaotic gravitational interactions between nearby planets.

[Telepathic Intruder]

All good points. In fact there may be a plethora of requirements, or there may be relatively few; we just don’t know because a single data element cannot provide a statistical basis. There are some absolute requirements for life, and a mountain of factors that are speculative. Assuming it’s carbon-based, life needs water—therefore an atmosphere, a temperature suitable for carbon compounds, an energy source, and a very long time of relatively stable conditions for evolution to take place. But there are a lot of additional conditions that are necessary for those conditions to even exist.