[–] DessertFox 0 points 1 point 1 point (+1|-0) ago
It's hard to disagree with you, but we should note that the habitable zone has been extended to include moons that are heated by tidal forces, or even planets that are heated largely by radioactive decay (like earth is).
The heat inside the planet is great for maintaining liquid states, but sunlight is a better source of usable energy for any life forms. I don't know if there are any life forms that could gain energy only from heat. It's theoretically possible, but the biology would be complex, probably too complex to emerge. Life can probably start with significantly less sunlight than we have. Or, there may be creatures with an entirely passive life, that exert no energy on their own (the biological version of RFID, more or less). That would be very interesting, but very hard to detect; its also debatable if they could be called lifeforms.
By the way, Japan's Akatsuki spacecraft is back on course for Venus orbit. The mission was partially abandoned in 2010 when it couldn't reach its intended orbit, but they are able to use plan B now. It'll start sciencing in December. I love Venus, we've ignored it for too long. It's so like Earth, but very different.
[–] TunaAndCucumbers 0 points 1 point 1 point (+1|-0) ago
Plus, the possibility of microbial life towards the tops of the Venusian atmosphere!
Though I don't think Akatsuki has the instruments to probe for something like that.