Unfortunately, I think Kepler 22-b is likely to turn out to have a run-away greenhouse effect like Venus. I'll be interested in the papers that get published once people have had time to construct models and run simulations, but based on past papers I've read on exoplanet habitability, it's a pretty borderline candidate.
The habitable zone moves outwards for planets with masses larger than Earth, due to their presumably thicker atmospheres, all else being equal.
I'll grant you that I don't know much about exoplanet study, but I think the key word here is "presumably". Obviously, planets more dense than earth have the POTENTIAL to have denser atmospheres, but their mechanisms for atmosphere generation may not be the same. IIRC, the earth owes a lot of its atmosphere to the early activity of bacteria and other micro organisms that pulled nitrogen and oxygen from seawater and rocks. Until we can see the atmospheres on other exoplanets and measure their density and composition, we can only guess as to the processes that created them.
The nitrogen in Earth's atmosphere is derived from the volcanic outgassing of N2 and ammonia, and from
cometary delivery. Nitrogen-fixing bacteria remove nitrogen from the atmosphere by incorporating it into nitrogenous organic compounds; some of these are later returned to the atmosphere by denitrifying bacteria, and some is
geologically sequestered. Some geologically sequestered biological nitrogen is eventually returned to the atmosphere by the weathering of the rocks that contain it, but the net effect of bacteria on Earth has been to remove nitrogen from the atmosphere over geological time, with
perhaps half of the nitrogen in Earth's early atmosphere having been removed by bacteria and geologically sequestered so far.
The story is similar for CO2; it originates from volcanic outgassing and cometary delivery, and most of it has been removed from the atmosphere by biological activity. On Earth, there are 2 main processes that remove CO2 from the atmosphere. One is the burial of carbon-rich biological material, which removes the carbon and leaves the oxygen in the atmosphere. The other is the abiotic reaction of silicate minerals with CO2 to from carbonate minerals. This process is greatly accelerated when silicate rock is exposed to rain, which absorbs CO2 to form carbonic acid, and it occurs very slowly in the absence of water or when the rock is submerged in the oceans, where the high PH inhibits the reaction. On Earth, the removal of CO2 by the weathering of exposed silicate rock outpaces the volcanic outgassing of CO2.
On an Earth-mass planet with a global ocean or with no precipitation, CO2 removal by silicate weathering would be outpaced by the addition of CO2 by volcanic outgassing, causing CO2 to build up in the atmosphere over time. On a super-Earth, tectonic processes would be more vigorous and the volcanic outgassing of CO2 and nitrogen would be more rapid than it is here on Earth, and the increased volcanism would also result in a more rapid release of primordial water from rocks in the mantle, which means that a super-Earth is more likely to have a global ocean. These factors favour super-Earths which are further out from their stars, since they can remain at a comfortable temperature at distances which would cause global glaciation on Earth.
Planet formation is a highly non-linear, chaotic process, and the eventual conditions on a planet are sensitive to chance collisions, ejections and migrations during the formation of the planetary system, as well as on elemental abundances around a star, which are affected by the number and the types of nearby supernovae that contributed to the proto-planetary disk, and the degree of radioactive heating, which is important for the differentiation of planetary interiors, is dependent also on the period of time that's elapsed between supernova contributions and planet formation, but comparisons can be made on an all-else-being-equal basis between Earth and exoplanets with poorly constrained atmospheric conditions (in this case, only the radius and the orbital period are known; the mass is just estimated and nothing at all is known about the atmosphere).
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