Friday, January 12, 2018

URSP Student Camerian Millsaps Simulates Exoplanet Photochemistry and Climate

If you’ve ever traveled internationally, watched a movie, or read a novel, you know that immersion in another world can be refreshing or even life-changing. So here’s a quiet reminder: there are, quite literally, other worlds in our galaxy - planets with different gravities, compositions, climates, and - possibly - life. And it is scientifically possible to, with some confidence, determine what it might be like to stand on their surfaces.

Although present technologies only permit detailed study of the largest exoplanets, planned and proposed space telescope missions would allow for more detailed study of small, rocky worlds like ours. But with several thousand such worlds discovered, which ones do you study first? If you’re observing because you hope to detect signs of life, one way to improve your odds is to observe planets orbiting within zones more likely to support surface liquid water. But there’s a huge variation in the likelihood of habitable conditions, even within that zone. Just like on Earth, small changes in atmospheric chemistry can have major climate impacts.

My research is an outgrowth of work conducted during Dr. Mike Summers’ astrobiology class, and it serves as an intermediary step between preliminary detection and detailed atmospheric characterization of rocky exoplanets. I use an open-source computer program to simulate possible surface conditions on one rocky planet (K2-3 d), which orbits along the hot inner edge of its star’s nominal “habitable zone.” I’ve been making incremental changes to one of several built-in atmospheric chemistry templates, and then applying that template to K2-3 d to see what happens to its photochemistry and surface temperatures. In doing this, I’m helping to determine if it’s a good target for follow-up observations. If 99% of plausible simulated atmospheres produce surface temperatures inhospitable to even the hardiest bacteria on earth, searching for signs of life on K2-3 d may not be a wise use of telescope time.

So far, my biggest challenges have involved building data-science and programming skills on the fly. Adding K2-3 d’s host star to the program was far more difficult than anticipated. Although a stellar spectra is effectively two columns of numbers (wavelength and flux)... it took more than two months to find and gather that data from multiple sources, convert it into a human-readable format, fill in or bypass documentation gaps, and account for different resolutions, units, and scalings. I expected to have difficulties simulating complicated feedback processes… not gathering data on a fundamental parameter! But it was fascinating to learn about another discipline’s data management practices, and I appreciated the opportunity to gain that skillset.