Habitable Venus

[Cray]

I believe some studies show that magnetic fields are not a major factor anyway. What prevents water from escaping to the upper atmosphere in the first place and be split by radiation is a cold trap.

A low inclination planet creates relatively large arctic regions because the poles never get tilted toward the sun for half the year. They get perpetual twilight and night time. Large ice caps would be a self-reinforcing cold trap: high albedo lowers temperatures and accumulates more ice.

On slow rotation, some say a Venus rotating close to Earth's rate would not be habitable due to the lack of cloud formation on the dayside to reflect sunlight, which is twice as strong. A slow-rotating Venus would still have the cloud formation which is helpful.

I have to wonder about that. At Earth-like levels of illumination and 24-hour rotation, there's plenty of time to develop large clouds. It's a daily cycle in Florida during the summer: clouds boil up from water throughout the day, then rain out in the evening. With twice the sunlight, you should be able to get more water into the air in less time. However, I'm not a meteorologist.

So, some factors toward a 0AT habitable Venus:
1. Low inclination for proportionally large ice caps (vs. any other planet at 0.7AU from a G2V star)
2. 50% or less water coverage, which is enough (?) for plate tectonics but would increase albedo, land generally having a higher albedo than water
3. Thinner atmosphere, perhaps 0.5 to 0.7-bar at sea level

Here's a fun page: https://www.astro.indiana.edu/ala/PlanetTemp/index.html

Using values of a bond albedo of 40 (vs 29 for Earth), average distance of 0.723AU, and 0.5 greenhouse effect (vs 1 for Earth), the result is rather warm: 38C average versus Earth's average of 15. Do those input values look sensible?

What would a 38C planet be like?