As above, not so below: Ion fractionation in planetary analog ices.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41950334.
- Also identified by DOI 10.1126/sciadv.ady6763 and PMC identifier 13060609.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The geophysical evolution and astrobiological potential of ocean worlds are indelibly linked to the chemical compositions of their oceans and ice shells. In the absence of direct measurements, empirical estimates of subsurface ocean compositions have relied on the assumption that the ionic compositions of ice shell surfaces are representative of their underlying ocean compositions. Here, we present experimental results demonstrating that ion fractionation-the differential entrainment of ion species in forming ices-is likely a prevalent process on ocean worlds, suggesting that planetary ice shell compositions do not directly reflect their underlying ocean compositions. We measure in-ice depletions and amplifications of relative ion concentrations ranging between -40 and +77%, compared to the parent fluid composition. Although this may complicate the interpretation of spacecraft data, ion fractionation provides a mechanism for generating compositionally diverse ices that could help explain the geological complexity of planetary ice shells.