Observing the Atmospheres and Surfaces of Earth Analogs

近几十年来，已经发现了数千颗围绕其他恒星运行的行星。这些世界是如此遥远，以至于在最好的情况下，它们看起来像未解决的点，但我们仍然可以仅仅基于光盘集成光来了解它们。的确，它们缺乏详细的观测，但它们的数量和多样性弥补了这一点：系外行星为我们提供了解决行星科学难题的杠杆，包括大气环流、云的形成和地球化学循环。

Thousands of planets have been discovered orbiting other stars in recent decades. These worlds are so distant that they appear as unresolved dots in the best of cases, but we can still learn about them based solely on disc-integrated light. Indeed, what they lack in detailed observations, they make up for in quantity and diversity: exoplanets provide us with leverage to crack hard problems in planetary science including atmospheric circulation, cloud formation, and geochemical cycling. The James Webb Space Telescope (JWST) is a 6.5 meter infrared telescope that NASA will launch in fall 2018. It will be the first instrument capable of characterizing the atmospheres of temperate terrestrial exoplanets, and the only telescope capable of measuring their thermal emission until the mid 21st century. Canada is poised to be a leader in the use of JWST for exoplanet observations and my proposed research program will maximize our ability to design, reduce and analyze observations of transiting temperate terrestrials. By working closely with the JWST/NIRISS team at l'Université de Montréal, we will help them design and implement their Guaranteed Time Observations of transiting planets, and my group will be prepared to apply for and analyze Early Release Science, which will become public in 2019. The next flagship after JWST, the Wide Field Infrared Survey Telescope (WFIRST), will be equipped with a coronagraph for imaging nearby planetary systems in reflected light. Even though planets will be unresolved dots in the images, their brightness and color will vary as rotational and orbital motion bring different surface features into view. My group will help determine the measurement precision, time resolution, and spectral resolution necessary to measure planetary obliquity and construct surface maps. The second generation of space-based high-contrast imaging will focus on Earth twins orbiting nearby stars. Exo-cartography will help us understand whether these planets have plate tectonics and volatile cycles like we have on Earth, and will therefore be a key step in establishing the long-term habitability of these worlds.