Therefore, interstellar panspermia events are related to the average density of stellar systems containing habitable planets.
The target planet must also at least be habitable to allow seeding by a single organism.
For a continental area of more than 90 % of the total surface, no habitable solutions also meeting the requirement of orbital stability exist.
For example, the radial galactic metallicity gradient determines isotope concentrations, silica and magnesium concentrations, etc., all of which are important for forming habitable planetary systems.
Naturally we still have to answer the most fundamental question before we are able to define habitable zones.
The requirements for plate tectonics of water and mass are also independently requirements for habitable planets.
As long as any cloud cover thins to some extent during the day, the extension is comfortably habitable without further heating.
So these requirements for plate tectonics are already fundamental conditions for a habitable planet.
