Welcome to my site! I am a postdoctoral fellow in the Department of Astronomy and Astrophysics at UC Santa Cruz investigating chemical and aerosol processes in planetary atmospheres. I will move to the Carnegie Institution for Science Earth & Planets Lab in Fall 2021 to become a permanent staff scientist. Learn more about my research and areas of study below.


I received my PhD in Planetary Science from Caltech, where I worked on modeling aerosols and chemistry in the atmospheres of Venus, Mars, Titan, and Pluto, and the atmospheric evolution of terrestrial worlds orbiting M dwarf stars. After graduation, I spent a year at NASA Ames Research Center as a NASA Postdoctoral Program Fellow and three years at UC Berkeley as a 51 Pegasi b Postdoctoral Fellow, where I focused on understanding aerosols in exoplanet and brown dwarf atmospheres.

Check out my CV and Google Scholar Profile for more information: 





Detailed exploration of the atmospheres of Solar System bodies have allowed for unsurpassed discoveries and surprises. I have led and been a part of several investigations into the current unsolved mysteries of these familiar places, including the sulfuric acid clouds of Venus, the puzzling presence of methane on Mars, the complex chemistry of Titan, and the ethereal hazes of Pluto.


The quest to characterize the atmospheres of exoplanets and brown dwarfs has accelerated in recent years thanks to new observing strategies and methods of analysis. In support of the deluge of data from current and future telescopes, I have conducted several modeling studies that apply what we have learned about photochemistry and cloud physics in the Solar System to these distant worlds.




The Community Aerosol and Radiation Model for Atmospheres (CARMA) is a 1D forward model that calculates the size distribution of aerosol particles in a planetary atmosphere. The model calculates rates of particle nucleation (homogeneous and heterogeneous), condensational growth, coagulation, evaporation, sedimentation, advection, and diffusion from first principles (e.g. Pruppacher & Klett 1978) and balances these rates to arrive at the equilibrium particle distribution. The size distribution is described by bins instead of a parameterized shape, such as the lognormal distribution.

CARMA was originally developed by Turco et al. (1979) and Toon et al. (1979) and has undergone several updates (e.g. Jacobson et al. 1994, Ackerman et al. 1995). While it has been mostly used to simulate Earth aerosol processes, it has been extended to Solar System atmospheres as well.

I use CARMA to generate aerosol size distributions in planetary atmospheres for a variety of investigations. I have used CARMA to simulate the sulfuric acid clouds of Venus to understand why its upper haze is variable, and the hydrocarbon hazes of Pluto to explain observations by New Horizons (see below). I am now developing a version of CARMA that can be applied to warm and hot exoplanet atmospheres, which involves including a host of higher temperature condensates. Some results of my work and those of my collaborators on this endeavor can be found in Gao et al. (2018) and Powell et al. (2018)


The Caltech/JPL 1D Photochemical and Transport Model (KINETICS) calculates the abundance profiles of chemical species in a planetary atmosphere in response to (1) photolysis of species by high energy photons from the host star, (2) thermochemical reactions between species, (3) transport by diffusion and advection, and (4) upward and downward fluxes of chemical species from below and above the model domain (e.g. volcanic emission). It can be applied to any planetary atmosphere and has a library of more than 1,000 species and 20,000 reactions. 

KINETICS was originally developed by Allen et al. (1981) and has since been applied to numerous planetary atmospheric studies covering every atmosphere in the Solar System, exoplanet atmospheres, and several exospheres of giant planet icy satellites. 

I use KINETICS to explore how Solar System analogs evolve when they are in orbit of other stars. In particular, terrestrial worlds around M dwarfs have captivated our imaginations due to their abundance and relative ease of characterization. However, M dwarfs' spectra are noticeably different from those of the Sun, with a much higher far-UV flux compared to their near-UV flux. I have investigated how the atmospheres of Mars-like (see below) and Titan-like planets (Lora et al. 2018) would fare around an M dwarf. I now focus on Venus, as Venus-like worlds may make up a large fraction of planets discovered by the TESS mission. ​



Thank you for your interest in my research! Feel free to contact me using the form below, or via email displayed at the top of the site. I would love to hear from you!

Peter Gao

Department of Astronomy and Astrophysics

University of California, Santa Cruz



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