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ye_olde_astronaut OP t1_j6kysjr wrote

Reply to comment by sintos-compa in Habitable Planet Reality Check: TOI-700e Discovered by NASA’s TESS Mission by ye_olde_astronaut

Not good and zero. Mars, with an 1.52 AU orbit, is just within the 1.70 AU outer limits of the habitable zone as defined by the "maximum greenhouse" limit. But its mass is too small to hold onto an atmosphere and sustain the geologic activity support the carbonate-silicate cycle that acts as a thermostat on rocky planets. Studies suggest that a planet needs to be twice the mass of Mars to do that. The inner edge of the conservatively defined habitable zone is 0.97 AU. Venus, with an 0.72 AU orbit, is too close to the Sun to be habitable by this definition (contrary to claims frequently found in the popular press).

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sintos-compa t1_j6l1jql wrote

Are those conclusions we could draw from what we could observe at 100 ly?

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ye_olde_astronaut OP t1_j6l3ssf wrote

For TOI-700, we know the properties of the star, the radii of the planets and the characteristics of their orbits. My quick assessment is based on the same info for Venus and Mars in our solar system.

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