A New Global Chemical Equilibrium Code: Refractory Element Signatures in Super-Earths and Sub-Neptunes
Year: 2026
Type: preprint
Abstract: The atmospheres of super-Earths and sub-Neptunes can be strongly modified by chemical exchange with their molten interiors during long-lived magma ocean phases. Interpreting atmospheric observations requires fast models that self-consistently couple atmospheric chemistry to the composition of the planetary interior. We present an updated, CPU-based implementation of the global chemical equilibrium (GCE) framework from H. E. Schlichting & E. D. Young (2022), which computes the equilibrium composition of a coupled metal-silicate-gas system. The numerical solver has been improved using a gradient-based optimizer, reducing the computational cost of solving the chemical network by more than two orders of magnitude and enabling large parameter studies. We apply the framework to a large synthetic population of planets and explore the imprint of bulk refractory composition of Mg, Si, and Fe on atmospheric properties in the end member case that hydrogen dissolution increases unbound with pressure. We consider planets with different masses, thermal states, and volatile inventories. We find that the atmospheric mass fraction and atmospheric metal mass fraction are primarily controlled by the temperature at the atmosphere-magma ocean interface and the planetary water budget, while the accreted hydrogen mass fraction plays a minor role because most hydrogen dissolves into the interior. For planets that accreted water, the refractory ratios Mg/Si and Fe/Si strongly influence carbon partitioning between the gas, silicate, and metal phases, producing large variations in atmospheric metal mass fraction and C/O ratios. These results demonstrate that atmospheric compositions of sub-Neptunes depend sensitively on both the volatile inventory and the bulk composition of rocky material, providing new constraints for interpreting atmospheric observations. The new GCE code is open-source.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: NCCR PlanetS: Origin, evolution and characterisation of planets, GUIDING QUESTION: HOW TO ACQUIRE SUSTAIN AND NURTURE LIFE-ESSENTIAL CHEMICAL INGREDIENTS ON THE SURFACE OF ROCKY PLANETS? BUILDING A HABITABLE ENVIRONMENT ON INNER SOLAR SYSTEM ROCKY SURFACES REQUIRES THE LIFE-ESSENTIAL CHEMICAL INGREDIENTS (C N O H S AND P) TO JOURNEY THROUGH A SERIES OF ASTRONOMICAL PLANETARY GEOLOGICAL AND GEOCHEMICAL PROCESSES DURING PLANET FORMATION AND EARLY PLANETARY EVOLUTION. HOWEVER IN MOST STUDIES ONLY ONE OR FEW OF THESE STEPS ARE INVESTIGATED IN ISOLATION AS CONDITIONS OF HABITABILITY AND THE CONSEQUENCES OF MULTIPLE PATHWAYS THAT MAY BE FEASIBLE ARE NOT RIGOROUSLY EXPLORED. SIMILARLY MOST STUDIES TRACKING THE IMPACT OF PREBIOTIC PROCESSES CONSIDERED THE ORIGIN OF WATER ALONE AND COMPREHENSIVE STUDIES ON A COMBINATION OF LIFE-ESSENTIAL ELEMENTS ARE LACKING. IN ORDER TO EVALUATE THE PATHWAYS THAT MAY LEAD TO EARLY HABITABLE CONDITIONS IN MULTIPLE PLANETARY SURFACES BUT SUSTENANCE ONLY IN A SUBSET AN INTERDISCIPLINARY APPROACH TO STUDY THE EARLY CYCLES OF ALL KEY INGREDIENTS ARE NECESSARY. THIS CAN 8 NAI NODE PROPOSAL AIMS TO CONSTRAIN THE PATHWAYS THAT LEAD TO THE ACQUISITION SUSTENANCE AND NURTURING OF THE LIFE-ESSENTIAL CHEMICAL ELEMENTS AT THE SURFACE AND NEAR-SURFACE ENVIRONMENTS OF ROCKY DIFFERENTIATED PLANETARY BODIES LEADING TO HABITABILITY AND POTENTIALLY DRIVING THE FORMATION OF PREBIOTICALLY-RELEVANT ORGANIC MOLECULE PRECURSORS WITHIN THE FIRST BILLION YEARS OF A PLANET S EVOLUTION. OUR TEAM MEMBERS BRING EXTENSIVE EXPERTISE IN ASTROPHYSICS GEOLOGY GEOCHEMISTRY GEOPHYSICS FLUID AND ATMOSPHERIC DYNAMICS CLIMATE SCIENCE AND ORGANIC CHEMISTRY; AN OVERARCHING GOAL IS TO TRACE THE LIFE-ESSENTIAL ELEMENTS FROM PROTOPLANETARY DISKS TO EARLY PREBIOTIC MOLECULES ON THE SURFACES OF ROCKY PLANETS WITH A PARTICULAR EMPHASIS ON THE FEEDBACKS AMONG INTERIOR SURFACE AND ATMOSPHERIC PROCESSES. WE WILL USE OBSERVATIONS FROM OUR OWN SOLAR SYSTEM IN TERMS OF COMPARATIVE PLANETOLOGY BUT WILL ALSO CONSTRUCT POSSIBLE PATHWAYS THAT MAY LEAD TO THERMO-CHEMICAL HABITABILITY WHICH CAN BE UTILIZED FOR EXPLORATION OF OTHER SOLAR SYSTEMS IN SEARCH FOR LIFE. THE PROPOSED RESEARCH COMPLEMENTS THE ACTIVITIES OF THE CAN 7 TEAMS BECAUSE NONE OF THE CURRENT TEAMS ARE INVESTIGATING THE CYCLES OF THE KEY INGREDIENTS DURING DIFFERENTIATION AND EARLY TECTONO-MAGMATIC AND GEOCHEMICAL EVOLUTION OF ROCKY PLANETS. OUR PROPOSAL WILL BRING IN THE UNIQUE INTERDISCIPLINARY PERSPECTIVE OF CYCLES OF KEY INGREDIENTS OF LIFE THROUGH DEEP TIME FROM GEOLOGIC PLANETARY GEOPHYSICAL AND GEOCHEMICAL PERSPECTIVES. GIVEN THE INTERDEPENDENT NATURE OF THE PROPOSED ACTIVITIES AMONG SEEMINGLY DISPARATE FIELDS OF RESEARCH THE SCOPE OF THIS PROPOSAL CAN ONLY BE SUPPORTED THROUGH AN INSTITUTE WITHOUT WALLS . RELEVANCE TO THE GOALS OF THE ASTROBIOLOGY PROGRAM: THE PROPOSED INVESTIGATION IS RELEVANT FOR SEVERAL OF THE GOALS OF THE ASTROBIOLOGY PROGRAM AS OUTLINED IN THE 2015 STRATEGY INCLUDING THE CENTRAL THEMES OF CONSTRUCTING HABITABLE WORLDS AND IDENTIFYING EXPLORING AND CHARACTERIZING ENVIRONMENTS FOR HABITABILITY AND BIOSIGNATURES . OUR PROPOSAL WILL DIRECTLY ADDRESS QUESTIONS SUCH AS HOW DOES THE STORY OF EARTH IN PARTICULAR IT S PAST INFORM US ABOUT HOW THE CLIMATES ATMOSPHERIC COMPOSITIONS INTERIORS AND BIOSPHERES OF PLANETS CAN CO-EVOLVE? BECAUSE OUR TEAM WILL STUDY THE INTERACTIONS OF INTERIOR ATMOSPHERE AND CLIMATE IN THE FIRST BILLION YEARS OF A ROCKY PLANETS EVOLUTION KEEPING IN MIND THE HISTORY OF THE EARTH AS AN ANALOG. OUR PROPOSAL WILL ALSO DIRECTLY ADDRESS QUESTIONS SUCH AS WHAT ARE THE FUNDAMENTAL INGREDIENTS AND PROCESSES THAT DEFINE A HABITABLE ENVIRONMENT? BECAUSE WE WILL TRACK THE FATE OF THE LIFE-ESSENTIAL ELEMENTS THROUGH THE FUNDAMENTAL PROCESSES OF PLANET FORMATION AND EARLY GEOLOGIC AND BIOGEOCHEMICAL EVOLUTION WITH THE GOAL OF OUTLINING POSSIBLE PATHS THAT ARE OR ARE NOT FAVORABLE IN FINALLY HARBORING THE COHNSP SPECIES AT THE PLANETARY SURFACES., G3188738659, Planets and their deep volatile reservoirs, G8505061131, G8864495428, G8961992780
OpenAlex ID: W7160828051