Detection of phosphates originating from Enceladus’s ocean
|Author:||Postberg, Frank1; Sekine, Yasuhito2,3; Klenner, Fabian1;|
1Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany
2Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Tokyo, Japan
3Institute of Nature and Environmental Technology, Kanazawa University, Ishikawa, Japan
4Space Science Division, Space Sector, Southwest Research Institute, San Antonio, TX, USA
5Leibniz-Institute für Oberflächenmodifizierung, Leipzig, Germany
6Institute of Chemical Technology, University of Leipzig, Leipzig, Germany
7Laboratory for Atmospheric and Space Physics (LASP), University of Colorado, Boulder, CO, USA
8Institute for Extra-cutting-edge Science and Technology Avantgarde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanagawa, Japan
9Astronomy Research Unit, University of Oulu, Oulu, Finland
10Institut für Raumfahrtsysteme, Universität Stuttgart, Stuttgart, Germany
|Online Access:||PDF Full Text (PDF, 17.4 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe20230929137809
|Publish Date:|| 2023-09-29
Saturn’s moon Enceladus harbours a global ice-covered water ocean. The Cassini spacecraft investigated the composition of the ocean by analysis of material ejected into space by the moon’s cryovolcanic plume. The analysis of salt-rich ice grains by Cassini’s Cosmic Dust Analyzer10 enabled inference of major solutes in the ocean water (Na+, K+, Cl-, HCO3-, CO32-) and its alkaline pH. Phosphorus, the least abundant of the bio-essential elements, has not yet been detected in an ocean beyond Earth. Earlier geochemical modelling studies suggest that phosphate might be scarce in the ocean of Enceladus and other icy ocean worlds. However, more recent modelling of mineral solubilities in Enceladus’s ocean indicates that phosphate could be relatively abundant. Here we present Cassini’s Cosmic Dust Analyzer mass spectra of ice grains emitted by Enceladus that show the presence of sodium phosphates. Our observational results, together with laboratory analogue experiments, suggest that phosphorus is readily available in Enceladus’s ocean in the form of orthophosphates, with phosphorus concentrations at least 100-fold higher in the moon’s plume-forming ocean waters than in Earth’s oceans. Furthermore, geochemical experiments and modelling demonstrate that such high phosphate abundances could be achieved in Enceladus and possibly in other icy ocean worlds beyond the primordial CO2 snowline, either at the cold seafloor or in hydrothermal environments with moderate temperatures. In both cases the main driver is probably the higher solubility of calcium phosphate minerals compared with calcium carbonate in moderately alkaline solutions rich in carbonate or bicarbonate ions.
|Pages:||489 - 493|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
F.P., F.K., Z.Z., J.K.H., N.K. and L.N. were supported by the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Consolidator grant no. 724908-Habitat OASIS). Y.S. and T.Shibuya have been supported by Grants-in-Aid for Scientific Research from the Japan Society for Promotion of Science (grant nos. JP22K21344, JP17H06455 and JP17H06456). R.S. has been supported by the German Aerospace Centre through grant no. 50OH1501. B.A. acknowledges support by the German Science Foundation through grant no. AB 63/25-1. Z.Z. was supported by the Chinese Scholarship Council (grant no. 201604910894). C.R.G. was supported by Southwest Research Institute (grant no. 15-R6248) and by Simons Collaboration on the Origins of Life (grant no. 511570FY20). Open access funding provided by Freie Universität Berlin.
All CDA data used for this work are listed in Extended Data Table 1 and are archived on PDS–SBN, at https://sbn.psi.edu/pds/resource/cocda.html. Data from the LILBID analogue experiment reproducing CDA data and geochemical experiments are available in the Zenodo public repository at https://doi.org/10.5281/zenodo.7703848.
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