What Does Heavy Water Mean?

Venus day looks and is apocalyptic in every meaning of the word, probes have found that there's a lot of sith called heavy water in its atmosphere. Heavy water just kind of switch out that hydrogen for something called juterium, which is like a heavier version of hydrogen. If that water existed in liquid form, what the odds that venus was habetable at some point? You now, it's not unlikely, even though to day it looks impossible. Could you imagine, what does pasphemus look like? Yes, it's almost like trying to reconstruct what happened after like an all consuming fire.