The Pursuit of A Meticulous Chemical Survey of Exoplanet Atmospheres

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits. However, the essential nature of these planets remains largely mysterious. We have poor observational insights into how the chemistry of a planet is linked to its formation environment, or how the type of host star drives the processes controlling the planet’s birth and evolution.

Current facilities have begun the reconnaissance of exoplanetary atmospheres. The Hubble Space Telescope (HST) has been utilised to conduct observations of tens of worlds, with a wide variety of planet sizes and temperatures. These data have allowed for the first “population” studies of exoplanet atmospheres to be undertaken. The G141 grism of the Wide Field Camera 3 (WFC3), which provides sensitivity to water in these atmospheres, has been central to these efforts and has characterised planets in both transmission and emission.

I will discuss the latest outcomes of homogenous population studies with HST WFC3, highlighting the key results and findings in the search for chemical trends as a function of the bulk parameters of a planet. Furthermore, the limitations of current approaches will be presented, including data quality, the potential biases in the current analysis methods, and lack of rigorous population-level target selection.

In the next few years, the quality and quantity of space-based data will drastically increase thanks to JWST, Twinkle and Ariel. These new facilities will probe the atmospheres of hundreds of planets in unprecedented detail, triggering a substantial shift in our understanding of planetary science on a galactic scale. However, to maximise the science yield of these missions, and be sure that the data is correctly interpreted, we must learn lessons from the currently available datasets.

I will discuss how we can use the results and, at times, failings of these previous endeavours to develop clear strategies for target selection and data analysis. Additionally, I will present projects which seek to understand the key capabilities and niches of these space-based observatories, to help develop strategies to exploit the synergies and complementarities between different facilities in an attempt to construct a meticulous chemical survey of exoplanet atmospheres.