Japan Geoscience Union Meeting 2023

Presentation information

[J] Online Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS20] Aqua planetology

Fri. May 26, 2023 10:45 AM - 12:15 PM Online Poster Zoom Room (21) (Online Poster)

convener:Yasuhito Sekine(Earth-Life Science Insitute, Tokyo Institute of Technology), Hidenori Genda(Earth-Life Science Institute, Tokyo Institute of Technology), Keisuke Fukushi(Institute of Nature & Environmental Technology, Kanazawa University), Takazo Shibuya(Japan Agency for Marine-Earth Science and Technology)

On-site poster schedule(2023/5/25 17:15-18:45)

10:45 AM - 12:15 PM

[MIS20-P08] Considering Earth's life from Enceladus' ocean

*Yasuhito Sekine1, Frank Postberg2, Shuya Tan3, Takazo Shibuya3, Takuya Saito3 (1.Earth-Life Science Insitute, Tokyo Institute of Technology, 2.Freie Universität Berlin, 3.JAMSTEC)

Keywords:icy satellites, Enceladus, chemical evolution

Saturn's moon Enceladus possesses a Na-carbonate-rich subsurface ocean. According to the in-situ analysis of plume materials erupting from the subsurface ocean, the Cassini spacecraft has revealed that seawater pH is alkaline, near 10, and that hydrothermal activity exists in the rock core. In addition to Na-carbonate-rich plume particles, a new type of phosphate-rich particle was recently discovered. Phosphorus (P) is a CHNOPS element essential for life on Earth, but of these, it is the least abundant in the Earth's aqueous environments. Throughout Earth's history, phosphorus has been the rate-limiting element of biological production. Based on the analysis of phosphate-rich particles of Enceladus, phosphate concentrations in the subsurface ocean would be 1000 times higher than in the Earth's oceans.

To understand the causative mechanism of the enrichment of phosphate in Enceladus' seawater, we performed hydrothermal reaction experiments and geochemical modeling. We find that alkaline (pH ~10) and carbonate-rich aqueous environments are essential for the phosphate enrichment, where calcium phosphate minerals are thermodynamically unstable compared to calcium carbonate minerals, releasing phosphate into liquid phase. Such alkaline carbonate-rich aqueous environments are commonly achieved in icy ocean worlds beyond the CO2 snowline of the Solar System. Phosphate could have been also enriched in similar alkaline carbonate-rich aqueous environments on early Earth, where earliest life on Earth might have utilized phosphorus as components of its building materials.