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The photochemical code originated from code developed by Kevin Zahnle and James Kasting, along with their students/postdocs/collaborators. After many decades, the development work carried out by various individuals resulted in many, MANY versions of the model, all with unique characteristics. This version of the code (originally called "The One True Code") was started by Mark Claire in an effort to merge the best features from these different code versions. In the process, Mark generalized the model to be less Earth-specific, and "modernized" the FORTRAN coding (he removed most of the vestigaes of F66 code and made it into an ugly F77/F90 hybrid - MUCH more could be done). Much of the effort was in removing hardcoding, and in allowing flexibility in the choice of wavelength grid, stellar flux, atmospheric species, and reactions used. The generalization of the code allowed us to develop “templates” for different types of planets. These templates contain different input files to get the code to run for different planet types - without having to change the Fortran code itself. This prevents the need to maintain different “versions” of the code for these different cases. Instead, all one has to do is move these input files to the correct directory (the script automates this for you), (re)compile the code, and then run it.

Contact email: Shawn Domagal-Goldman (

Ravi Kopparapu (

Mark Claire (

Shawn Domagal-Goldman and Ashley Horan coupled this model to a climate model that had been recently updated by Ravi Kopparapu and Ramses Ramirez, working for James Kasting. They had improved the model's water-vapor and CO2 absorption coefficients, and upgraded many of the numerical approaches. The coupling of the two models used logic originally developed by Antigona Segura. She also introduced much of the multi-star functionality used here.

Giada Arney added (or repaired) all of the Archean Earth templates. In the process, she added fractal hazes to the climate code and ensured coupling between photochem and clima, including self-cosnistent treatment of hazes.

Amber Britt fixed the modernEarth+Chlorine template, and incorporated the Mars template that was originally developed by Mark Claire and Meg Smith.

Mahmuda Afrin Badhan added a hot Jupiters template (not public yet), under the guidance of and based on the prior work of Ravi Kopparapu.

Ryan Felton added a Titan template to the model (not public yet), under the guidance of Eric Hébrard.

Eddie Schwieterman added templates for very high O2 conditions that could be caused by “Luger-Barnes” atmospheres where H is stripped away by high-energy radiation, leaving behind O-dominated atmospheres.

Eddie Schwieterman modified the numerical solver so the code would run for a wider range (of more oxidizing) redox conditions.

Eddie Schwieterman and Giada Arney developed tools to couple Atmos outputs to SMART, a line-by-line radiative transfer tool that we can use to predict the transit and reflected light spectra of the atmospheres we simulate.

Eddie Schwieterman, Giada Arney, Shawn Domagal-Goldman, Ashley Horan, Dillon Teal, Will Sluder, and Natasha Batalha addressed many (hundreds?) of compilations errors in the gfortran build of the previous Atmos code.

Eric Hébrard, Will Sluder, and Ryan Felton generalized the subroutine that calculated absorption crosss-sections (Xsections.f) and modernized many of the reaction rate constants. Ryan Felton also added a Titan template to the model (not public yet), under the guidance of Eric Hébrard.

Dillon Teal developed run scripts to automate input file generation, code compiling, and code convergence criteria.

Dillon Teal, Will Sluder, Amber Britt, and Shawn Domagal-Goldman did extensive edits to the code formatting to standardize things and make everything more readable.

Mark Claire removed files that didn't need to be under version control, exorcised pesky CRLF files, and implemented a basic branch management strategy.