There are other things that people
have discussed that are required for habitability.
Well, one of them is active geochemical turnover.
If a planet is not geologically active, eventually, nutrients and energy sources
will be used for life and the planet will essentially will run down.
There'll be no new energy supplies.
No new nutrients. We need active geo-chemical turnover.
First of all to recycle elements and nutrients in the crafts
that are needed by life, but also to generate chemical reactions
that can create new sources of energy, chemical disequilibrium that's
necessary for life to harness those energy supplies to grow.
There are a couple ways in which that might happen.
We might have, for example, plate tectonics where one plate subducts
under another plate and becomes heated and melts and these movements
of plates over the surface of a planet within its crust
create this turnover that's necessary to create the elements and nutrients
for life. Another way is active volcanism.
Volcanoes spewing lava and magma onto the surface of a planet also creates
turnover within the crust and generates new energy and nutrient supplies for life.