20 Criteria Absolutely Necessary To Have Life On Another Planet.

List of 20 prerequisites for life on any planet:

A location in a “safe” place in the galaxy, not close to any active regions, overactive stars, or black holes
Being attached to a stable star. Our sun, a G2 type is ideal
Having our host star the proper size, and with proper stable energy output
Being in an orbit in the “habitable” zone setting temperature in a fairly narrow region
Having several gas giant planets in the system for protection from orbiting debris
Having a near-circular orbit assuring that the heat input from the star does not vary much
A planet with the proper inclination as it goes around its orbit
Having a planet within a certain range of masses
Having a planet with a reasonable rotation rate
Having an atmosphere with the right composition and density
Having liquid water of the proper amount and composition
Having a good ratio between water (oceans) and land
Having hydrogen with specialized bonding to give water characteristics different than other substances
Having a satellite moon of the right size and distance
A planet of the proper mass
A planet with a liquid iron core to generate a magnetic field
A planet with a magnetic field of the proper strength
A rocky planet with a crust of the proper thickness to allow plate tectonics to occur
A planet with a good source of carbon – in the form to allow chemical reactions
A planet with a number of rare element chemicals which are essential to life forms.