A day or two ago there was musing about Venus' habitability prospects. Jupiter got the blame. (Leaving aside those of us who point out that Venus is habitable today 50 km altitude . . .)
In Reynolds' comments, some wondered how come Mars and Earth weren't noted. On Mars I can answer: because Vesta wasn't noted either. Jupiter starved the 1.5-5 AU region of material. Mars is on that edge of being considered a protoplanet, like Vesta (and Ceres etc.). When calculating models about Venus, Mars is just too small and too far.
Earth, I agree, needs more study. Today Earth and Venus run around our Sun at an 8:13 resonance. I doubt that this resonance is intrinsic. This latest study looks at a mere billion years ago: Venus was pushed inbound to this orbit, then. So Theia was already long-subsumed into Earth-Luna.
But again - why are we looking only at Venus, why not at Earth with it. Was there global-warming on Earth 1 bya? Global cooling?
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