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sintos-compa t1_j6kc1ah wrote

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

So is it better or worse chance to be habitable than Mars/Venus would have if discovered elsewhere with its current orbital patterns and size?

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Visual_Conference421 t1_j6kpbof wrote

I am not 100% sure I understand what you were asking, so I will give the simple things as to this planet. It is approximately the right size and mass to have the potential of a stable atmosphere (near earth size) and also in the habitable zone of its star. While a lot of factors can play into these things, having an atmosphere without being massive and super heavy, while also having a temperature range that allows for constant liquid water, are two big check marks on habitability.

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sintos-compa t1_j6ktvw7 wrote

If we found an exact copy of our solar system 100 Ly away, what odds would we give mars and Venus for having life with the observational techniques we possess today

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ye_olde_astronaut OP t1_j6kysjr wrote

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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