[Paper Review] The Origins Space Telescope: Towards An Understanding of Temperate Planetary Atmospheres

Jonathan J. Fortney, Tiffany Kataria+47 more|arXiv (Cornell University)|Mar 21, 2018

Stellar, planetary, and galactic studies2 references3 citations

TL;DR

The Origins Space Telescope (OST) proposes a mid- to far-infrared space observatory with active cooling (~4 K) to study temperate exoplanet atmospheres, particularly rocky planets in the habitable zones of M stars. Using the Mid-Infrared Imager, Spectrometer, and Coronagraph (MISC), OST will enable high-precision thermal infrared spectroscopy to constrain temperature structures and molecular abundances of biologically relevant gases like O3, CH4, H2O, and CO2, significantly advancing our understanding of planetary climate and potential habitability.

ABSTRACT

The Origins Space Telescope (OST) is one of four mission concepts currently being studied by NASA in preparation for the Astrophysics 2020 Decadal Survey. With active cooling (~4 K), OST will be sensitive in mid- to far-IR wavelengths, using imaging and spectroscopy to probe the furthest reaches of our galaxies, trace the path of water through star and planet formation, and place thermochemical constraints on the atmospheres of exoplanets ranging in size from Jupiter to Earth. This contribution to the Exoplanet Science Strategy committee discusses the significant advancements that the OST Mid-Infrared Imager, Spectrometer, and Coronagraph (MISC) instrument can make in studying cool planetary atmospheres. We particularly focus on the atmospheres of transiting rocky planets in the habitable zones of mid-to-late M stars. We discuss how OST thermal infrared observations can significantly enhance our understanding of the temperature structure and molecular abundances of biologically interesting gases on these worlds, including O3, CH4, H2O, and CO2.

Motivation & Objective

• To advance the understanding of temperate planetary atmospheres, especially those of rocky exoplanets in the habitable zones of mid-to-late M stars.
• To address the critical gap in thermal infrared observations for characterizing atmospheric composition and thermal structure of exoplanets.
• To enable high-precision measurements of biologically relevant gases such as O3, CH4, H2O, and CO2 in exoplanet atmospheres.
• To support the Exoplanet Science Strategy by providing a mission concept capable of delivering transformative data on planetary system formation and potential habitability.

Proposed method

• Utilize a cryogenically cooled (4 K) space telescope to achieve high sensitivity in mid- to far-infrared wavelengths.
• Deploy the Mid-Infrared Imager, Spectrometer, and Coronagraph (MISC) instrument for high-resolution spectroscopy and direct imaging of exoplanet atmospheres.
• Conduct thermal infrared observations of transiting rocky exoplanets to retrieve atmospheric temperature profiles and molecular abundances.
• Apply thermochemical modeling to interpret observed spectra and constrain atmospheric composition and energy balance.
• Leverage coronagraphy to suppress host star light and enhance detection of planetary thermal emission.
• Integrate data from multiple observing modes to build comprehensive atmospheric models of temperate exoplanets.

Experimental results

Research questions

• RQ1 How can mid- to far-infrared observations improve the characterization of temperature structure in temperate exoplanet atmospheres?
• RQ2 What molecular abundances of O3, CH4, H2O, and CO2 can be reliably retrieved from thermal emission spectra of rocky exoplanets around M stars?
• RQ3 To what extent can the MISC instrument detect and constrain disequilibrium chemistry indicative of biological activity?
• RQ4 How do atmospheric energy budgets and cloud properties affect the detectability of biosignature gases in temperate exoplanet atmospheres?
• RQ5 What are the optimal observing strategies for maximizing atmospheric characterization of transiting rocky planets using OST?

Key findings

• OST's MISC instrument will enable high-precision thermal infrared spectroscopy of temperate exoplanets, particularly those orbiting M stars, with sensitivity to detect key atmospheric gases.
• The mission will provide critical constraints on atmospheric temperature profiles and molecular mixing ratios, including biologically relevant species such as O3 and CH4.
• Thermal emission measurements from OST will allow for the detection of atmospheric energy redistribution and cloud feedback mechanisms in rocky exoplanets.
• The combination of imaging and spectroscopy will enable the study of atmospheric thermal structure and composition simultaneously, improving atmospheric modeling accuracy.
• OST's sensitivity in the mid- to far-infrared will allow for the detection of weak molecular features in cooler, temperate planets that are undetectable with current observatories.
• The mission will significantly enhance our ability to assess planetary habitability by probing atmospheric chemistry and energy balance in Earth-sized exoplanets.