For me, it started with sunsets. What is responsible for that burning splash of color across the horizon? When I learned in high school chemistry that it was due to the particular composition and particles in the atmosphere, I was transfixed.
Today, I’m broadly interested in the study of planets in the Solar System and planets around other stars, which are called exoplanets. I specifically investigate their atmospheres, and in particular, the potential clouds and smog found on other planets. I want to figure out how these aerosols form and evolve, how they affect the overall atmosphere chemically and physically, how they change our observations of distant worlds, and how they impact habitability. In short, I try to figure out how clouds and hazes work — in everything from brown dwarfs to gas giants to ice giants to terrestrial worlds. I do so by combining my past and ongoing laboratory work and atmospheric computer models.
During my PhD work at Johns Hopkins University under the advisorship of Prof. Sarah Hörst, I experimentally explored how smog compositions change with different atmospheric properties, from composition to temperature. I found that oxidized species, for exoplanets and for Neptune’s moon Triton, can be really important to smog formation and solid composition, in contrast to previous work from the Solar System that suggested only highly reducing atmospheres favor primarily hydrocarbon haze formation. I’m hard at work to implement these results into atmospheric models to compare with telescope observations both current and upcoming.
In addition, I run suites of atmospheric models to simulate how radiative transfer depends on various cloud and haze scenarios. For my postdoctoral work here at Arizona, I’m working closely with Professor Mark Marley to predict and interpret observations of all kinds of sub-stellar and planetary atmospheres from the Hubble Space Telescope and the newly operational JWST. I’m really excited to start seeing gaseous signatures of disequilibrium chemistry in these faraway worlds, and to try to connect these results to laboratory experiments on hazes.
Next up in the lab this fall, as an Arizona Sursum Fellow, I’m due to start a series of experiments exploring the role of the host star on the evolution of atmospheric haze. Haze primarily forms photochemically through dissociation and ionization of the gasses of the upper atmosphere. I hypothesize therefore that different stellar types with different ultraviolet fluxes should impact haze properties. We’ll be taking exoplanet-like hazes from my PhD lab and bombarding them with photons from UV lamps to measure the haze’s spectroscopic signatures before and after UV exposure.
Before grad school, I was at Barnard College of Columbia University in New York, where I majored in Astrophysics and spent a lot of time in various theatres (acting, dancing, set-building, stage managing, sight-seeing). I also ended up minoring in Science & Public Policy because I am passionate about improving the way we do science and who gets to participate in the scientific field. As part of that endeavor, I spent Fall 2019 in Washington, D.C. at the National Academies of Science, Engineering, and Medicine with the Space Studies Board. There I helped with the Astro2020 Decadal Survey, the Solar and Space Physics Midterm Report, and planning for the next Planetary Science Decadal Survey. I’m still always interested in policy, both as Science for Policy and Policy for Science. One day in the (perhaps distant) future, I anticipate making the jump to spending most of my time in that realm rather than a lab.
Finally, there is always a niggling question on my mind: why study distant planets when the climate here on Earth is in a state of emergency? This is something I think about often as an extrasolar planetary scientist. But, to me, this pursuit of knowledge is one of the things that makes us very human. I could give you the clichés about how learning about other climates teaches us ultimately about our own, or a screed about the importance of fundamental research. Honestly, though, that’s not why I’m here. I’m here because of that moment in high school chemistry — what makes the sunset so beautiful? We’re all here looking for meaning beyond ourselves. We are bits of discarded stardust yearning to understand its own atoms rearranged in countless ways – the universe working to know itself. It’s a privilege beyond measure that I can ask these questions and work toward making something like an answer to a small few of them. And I also want to know: Is someone else staring up at a distant sky wondering the same?
If you’d like to chat science (or apparently, philosophy of science), you can contact me on Twitter (@OF_FallingStars) or just follow along as I tweet about science, my running goals, and my hot takes on the nature of other planets.
Dr. Sarah Moran was awarded a Postdoctoral Research Development Grant (PRDG) from the University of Arizona for a project titled “Alteration of Planetary Hazes Related to Composition of Host Star”.
Each month we'll feature a Postdoctoral Scholar and their research, sharing their experiences from the UA, life in Arizona and their research interests.