PSJC #49 Oct 23 2009

Mark Swain (JPL)

Exoplanet Spectroscopy: a bright present, a brilliant future

[This is the abstract for the departmental colloquium; discussion during our seminar can draw from this.]

Spectroscopic detection of molecules in exoplanet atmospheres is revolutionizing exoplanet characterization. Today, it is possible to compare the temperature structure and composition of exoplanet atmospheres, explore the role of non-equilibrium chemistry, examine the effect of extreme radiation forcing, detect dynamical processes, and search for signatures of evolutionary history. Spectroscopy is revealing exoplanet atmospheres to be complex with numerous parallels to the atmospheres of planets in our own solar system. Recent observations demonstrate that broad, simultaneous, spectroscopic coverage is essential for resolving the temperature composition ambiguity present in exoplanet emission spectra. Given the significant number of bright exoplanet systems, there is an important discovery space accessible with modest sized telescopes. Today, exoplanet spectroscopy stands poised to radically alter our understanding of exoplanets and to explore questions more typical of planetary atmospheres in our own solar system.

While the Hubble and Spitzer space telescopes launched exoplanet spectroscopy, they have also proven the case for a purpose-built exoplanet spectroscopy mission with instantaneous broad wavelength coverage and extreme stability. The THESIS mission concept (Transiting Habitable-zone Exoplanet Spectroscopy Infrared Spacecraft) could accomplish these objectives at modest cost and with low technical risk. In the future, continued progress in the development of calibration methods will allow the James Webb Space Telescope and ground-based observatories to detect molecules in exoplanet atmospheres and may enable similar measurements with SOFIA. Although large telescopes have the potential to enable higher-resolution spectroscopy of small exoplanets, long-term, high-stability, broad spectral coverage measurements are needed to provide the framework in which to combine measurements from a variety of telescopes. Thus, THESIS has an important dual role in that it provides (1) unprecedented characterization measurements for a large sample of exoplanets and (2) provides the essential calibration framework to interpret measurements made with multiple large telescopes.