Hydrogen-carbon doubly superionic conduits of carbonic acids in planetary ices.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42102193.
- Also identified by DOI 10.1126/sciadv.aeb9271 and PMC identifier 13155303.
- Licence recorded as CC BY-NC.
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Abstract
Recent astronomical observations show that carbon dioxide (CO<sub>2</sub>) is widespread on planetary bodies, often coexisting with water (H<sub>2</sub>O). Crystalline carbonic acid (H<sub>2</sub>CO<sub>3</sub>), produced from CO<sub>2</sub>-H<sub>2</sub>O interactions, has been predicted and synthesized under high pressure, yet their dynamic behaviors under planetary interior conditions remain poorly understood. Here, we investigate the stability of CO<sub>2</sub>-H<sub>2</sub>O planetary ices across pressures from 0 to 500 gigapascals. Our simulations demonstrate that H<sub>2</sub>CO<sub>3</sub> and orthocarbonic acid (H<sub>4</sub>CO<sub>4</sub>) become dominant C─O─H compounds and evolve from molecular crystals into three-dimensional solids with increasing pressures. Particularly, both carbonic acids transform into a H-diffusive superionic phase and subsequently a C─H doubly superionic conduit enabled by interconnected oxygen polyhedral voids, where correlated motions between ions enhance the ionic conductivities. Moreover, the hydrogen in H<sub>2</sub>CO<sub>3</sub> exhibits strong anisotropic behaviors that may contribute to the nonaxisymmetric magnetic fields of ice giants. These findings further suggest that carbonic acid ices could sustain hydrogen-carbon transport, potentially enhancing convective volatile cycling in giant planet interiors.