MCMC-MELTS Inversion Code and Data for Olivine-Rich Units in Jezero Crater, Mars

Overview This repository contains the Python code and data used to model the crystallization of olivine-rich rocks in Jezero Crater, Mars. The included scripts implement a Markov Chain Monte Carlo (MCMC) algorithm coupled with MELTS thermodynamic modeling (via PetThermoTools) to invert the parental magma composition and crystallization conditions of the Margin Unit and Lake Haiyaha boulders. Scientific Goal The primary goal of this software is to test igneous formation hypotheses for the olivine-cumulate units discovered by the NASA Perseverance rover. By comparing simulated mineral chemistry (Olivine Fo# and Spinel TiO2/Cr2O3) against in-situ data from the PIXL instrument, this model provides probabilistic constraints on the primary melt composition. Contents MCMC_MarginUnit.py: The main Python script for running the MCMC-MELTS inversion. sim_final.csv: The raw output data containing the posterior distribution of accepted magma compositions and conditions. PMM mars compilation.xlsx: A compilation of Martian magma compositions from literature used for comparative analysis. Data Analysis-MU mars.ipynb: A Jupyter Notebook for visualizing the results and generating figures. Methodology The algorithm uses a Metropolis-Hastings sampler with a Simulated Annealing schedule to explore the parameter space of major oxide compositions, pressure, and oxygen fugacity. Likelihoods are calculated using a Gaussian distance metric (Z-score) between modeled and observed mineral phases. Dependencies This code requires Python 3.10+ and the following libraries: numpy, pandas, scipy, statsmodels, PetThermoTools, meltsdynamic. It also requires a local installation of AlphaMELTS. Citation This dataset and software are archived on Zenodo. If you use this code in your research, please cite this Zenodo record or the associated manuscript directly using the DOI provided on this page. Associated Manuscript: Dutta, S., Asimow, P. D., Farley, K. A.,Udry, A., Randazzo, N., & Williford, K. H.(2026). A shared magma source for theolivine‐rich units in Jezero crater, Mars.Journal of Geophysical Research: Planets,131, e2026JE009746. https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009746