Radioactive Decay as a Source of Chemistry and Heat in Pluto’s Subsurface Ocean

Kharsyntiew, Ariana Gayle (2025) Radioactive Decay as a Source of Chemistry and Heat in Pluto’s Subsurface Ocean. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Ariana Gayle Kharsyntiew (20MS151)) 20MS151_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

Radioactive Decay as a Source of Chemistry and Heat in Pluto’s Subsurface Ocean” This research investigates the role of radiogenic decay in influencing Pluto’s subsurface chemistry and thermal evolution. The study is grounded in the assumption that radioactive isotopes, such as 40K,235U,238U and 232Th decay and subsequent release of ionizing radiation could play a significant role in driving interior chemical as well as thermal processes. Using published models and data on Pluto’s surface and interior structure obtained from the New Horizons spacecraft flyby of Pluto in July 2025, this research explores the possibility that subsurface ocean radiolysis initiates the chemical formation of complex organic compounds (tholins) that could subsequently be extruded onto Pluto’s surface via surface fissures and cryovolcanic activity. Our model demonstrates how radiogenic processes, particularly involving the radiolysis of methane, vary with depth in Pluto’s ocean. The results reveal a non-linear interplay between temperature, pressure and methane stability-dynamics that could regulate the chemistry of Pluto’s interior and the potential for cryovolcanic activity at the surface. Our preferred scenario indicates that a minimum fraction of 0.42 times the radiogenic heating per unit mass known for the Earth could be su!cient to maintain a subsurface ocean inside of Pluto, preventing it from freezing, and at the same time drive chemical reactions that could lead to complex organic molecules becoming a significant component in Pluto’s subsurface ocean. The conclusions drawn from this research underscore the complex connections between Pluto’s thermal evolution, subsurface chemistry, and the potential for geological activity over extended periods. By drawing parallels with Earth’s own geological history, the study provides valuable insights into how distant, icy worlds like Pluto, can sustain environments conducive vi to chemical processes, thereby contributing to the broader

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