# What would be different about a heavy-water ocean world?

The water on Earth is primarily made of $$\ce{H2O}$$. I'm wondering about the conditions in a hypothetical $$\ce{D2O}$$ ocean world.

Would it be stable over geologic timescales (~$$\pu{0.1–2 Ga}$$)? What would be expected to be different, if anything? Would it affect the chemistry of its atmosphere, or appreciably change the incident radiation from its host star?

• The Oklo phenomenon would have looked different. – Loong Jan 31 '19 at 20:06
• A deuterium-rich world would make some important gasses substantially heavier (e.g. $\ce{D2}$, $\ce{D2O}$, $\ce{CD4}$) which would affect their concentration profile with altitude in the atmosphere ("scale heights") and could have some significant effect over geological timescales, such as significantly less $\ce{D2}$ escaping Earth compared to $\ce{H2}$ and making the atmosphere more reducing. – Nicolau Saker Neto Jan 31 '19 at 21:36
• The entire chemistry where hydrogen is involved could be different. Deuterium bond energy and length are different than those in hydrogen-1. It could affect the entire biochemistry. Consider also physical properties like viscosity and... ice made from heavy water SINKS in normal water. – Jakub Muda Jan 31 '19 at 22:30
• $\ce{D2O}$ has a higher melting point (3.8 C) than the of $\ce{H2O}$ of 0 C. On chemical side, expect reactions with hydrogen to proceed slowlier (heavy isotope effect) than normal. – Buttonwood Jan 31 '19 at 22:39
• I think the OP's multiple questions are not actual questions, but examples to help a community member answer the question. – A.K. Feb 1 '19 at 3:25