Telling twins apart: exo-Earths and Venuses with transit spectroscopy

The planned launch of the James Webb Space Telescope (JWST) in 2018 will herald a new era of exoplanet spectroscopy. JWST will be the first telescope sensitive enough to potentially characterize terrestrial planets from their transmission spectra. In this work, we explore the possibility that terrestrial planets with Venus-type and Earth-type atmospheres could be distinguished from each other using spectra obtained by JWST. If we find a terrestrial planet close to the liquid water habitable zone of an M5 star within a distance of 10 parsec, it would be possible to detect atmospheric ozone if present in large enough quantities, which would enable an oxygen-rich atmosphere to be identified. However, the cloudiness of a Venus-type atmosphere would inhibit our ability to draw firm conclusions about the atmospheric composition, making any result ambiguous. Observing small, temperate planets with JWST requires significant investment of resources, with single targets requiring of the order of 100 transits to achieve sufficient signal to noise. The possibility of detecting a crucial feature such as the ozone signature would need to be carefully weighed against the likelihood of clouds obscuring gas absorption in the spectrum.

[1]  W. Traub,et al.  TRANSITS OF EARTH-LIKE PLANETS , 2009, 0903.3371.

[2]  S. Aigrain,et al.  Hst hot jupiter transmission spectral survey: Detection of water in HAT-P-1b from WFC3 near-IR spatial scan observations , 2013, 1308.2106.

[3]  S. Aigrain,et al.  The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations , 2012, 1210.4163.

[4]  Clive D Rodgers,et al.  Inverse Methods for Atmospheric Sounding: Theory and Practice , 2000 .

[5]  Sarah Kendrew,et al.  Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching , 2015, 1501.06349.

[6]  L. Kaltenegger,et al.  EFFECT OF UV RADIATION ON THE SPECTRAL FINGERPRINTS OF EARTH-LIKE PLANETS ORBITING M STARS , 2015, 1506.07202.

[7]  L. Koesterke,et al.  Sodium Absorption from the Exoplanetary Atmosphere of HD 189733b Detected in the Optical Transmission Spectrum , 2007, 0712.0761.

[8]  C. Griffith,et al.  Disentangling degenerate solutions from primary transit and secondary eclipse spectroscopy of exoplanets , 2013, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[9]  C. Newhall,et al.  Fire and mud: eruptions and lahars of Mount Pinatubo, Philippines , 1998 .

[10]  F. Selsis,et al.  Potential biosignatures in super-Earth atmospheres I. Spectral appearance of super-Earths around M dwarfs , 2011 .

[11]  A. Lacis,et al.  A description of the correlated k distribution method for modeling nongray gaseous absorption, thermal emission, and multiple scattering in vertically inhomogeneous atmospheres , 1991 .

[12]  F. Selsis,et al.  Potential biosignatures in super-Earth atmospheres II. Photochemical responses. , 2013, Astrobiology.

[13]  G. C. Augason,et al.  Aircraft observations of Venus' near-infrared reflection spectrum: Implications for cloud composition , 1974 .

[14]  H. Rauer,et al.  Atmospheric effects of stellar cosmic rays on Earth-like exoplanets orbiting M-dwarfs , 2015, 1511.04920.

[15]  S. Hawley,et al.  The effect of a strong stellar flare on the atmospheric chemistry of an earth-like planet orbiting an M dwarf. , 2010, Astrobiology.

[16]  A. Watson,et al.  Venus Was Wet: A Measurement of the Ratio of Deuterium to Hydrogen , 1982, Science.

[17]  Mark Clampin,et al.  Transiting Exoplanet Survey Satellite , 2014, 1406.0151.

[18]  Kevin France,et al.  High stellar FUV/NUV ratio and oxygen contents in the atmospheres of potentially habitable planets , 2013, 1310.2590.

[19]  Sara Seager,et al.  ATMOSPHERIC RETRIEVAL FOR SUPER-EARTHS: UNIQUELY CONSTRAINING THE ATMOSPHERIC COMPOSITION WITH TRANSMISSION SPECTROSCOPY , 2012, 1203.4018.

[20]  Mark Clampin,et al.  Discovery and Characterization of Transiting SuperEarths Using an All-Sky Transit Survey and Follow-Up by the James Webb Space Telescope , 2010 .

[21]  Edinburgh,et al.  The Mid-Infrared Instrument for the James Webb Space Telescope: IV. The Low Resolution Spectrometer , 2015 .

[22]  Tyler D. Robinson,et al.  ABIOTIC OZONE AND OXYGEN IN ATMOSPHERES SIMILAR TO PREBIOTIC EARTH , 2014, 1407.2622.

[23]  Claus J. Nielsen,et al.  Spectroscopic Study of Aqueous H2SO4 at Different Temperatures and Compositions: Variations in Dissociation and Optical Properties , 2003 .

[24]  Steven Platnick,et al.  Remote sensing of cloud top pressure/height from SEVIRI: analysis of ten current retrieval algorithms , 2014 .

[25]  F. Taylor,et al.  Climate evolution of Venus , 2009 .

[26]  N. Narita,et al.  Titania may produce abiotic oxygen atmospheres on habitable exoplanets , 2015, Scientific Reports.

[27]  K. F. Palmer,et al.  Optical constants of sulfuric Acid; application to the clouds of venus? , 1975, Applied optics.

[28]  Joanna K. Barstow,et al.  Constraining the atmosphere of GJ 1214b using an optimal estimation technique , 2013, 1306.6567.

[29]  Nigel Bannister,et al.  Next Generation Transit Survey (NGTS) , 2013, Proceedings of the International Astronomical Union.

[30]  Joanna K. Barstow,et al.  On the potential of the EChO mission to characterise gas giant atmospheres , 2012, 1212.5020.

[31]  J. W. Hovenier,et al.  Interpretation of the polarization of Venus , 1974 .

[32]  Drake Deming,et al.  H2O ABUNDANCES IN THE ATMOSPHERES OF THREE HOT JUPITERS , 2014, 1407.6054.

[33]  Ryan C. Terrien,et al.  HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: NEW ESTIMATES , 2013, 1301.6674.

[34]  Henry E. Revercomb,et al.  Models of the structure of the atmosphere of Venus from the surface to 100 kilometers altitude , 1985 .

[35]  Robin Wordsworth,et al.  ABIOTIC OXYGEN-DOMINATED ATMOSPHERES ON TERRESTRIAL HABITABLE ZONE PLANETS , 2014, 1403.2713.

[36]  Victoria Meadows,et al.  Biosignatures from Earth-like planets around M dwarfs. , 2005, Astrobiology.

[37]  P. Drossart,et al.  Models of the global cloud structure on Venus derived from Venus Express observations , 2012 .

[38]  C. Bergh,et al.  The Runaway Greenhouse and the Accumulation of CO2 in the Venus Atmosphere , 1970, Nature.

[39]  Norman H Sleep,et al.  Habitable zone limits for dry planets. , 2011, Astrobiology.

[40]  G. Laughlin,et al.  Discovery and Characterization of Transiting Super Earths Using an All-Sky Transit Survey and Follow-up by the James Webb Space Telescope , 2009, 0903.4880.

[41]  S. Aigrain,et al.  The transit spectra of Earth and Jupiter , 2014, 1408.3914.

[42]  M. Burleigh.  The Next Generation Transit Survey , 2017 .

[43]  S. Calcutt,et al.  The NEMESIS planetary atmosphere radiative transfer and retrieval tool , 2008 .

[44]  Cfa,et al.  IMPACT OF ATMOSPHERIC REFRACTION: HOW DEEPLY CAN WE PROBE EXO-EARTH'S ATMOSPHERES DURING PRIMARY ECLIPSE OBSERVATIONS? , 2013, 1312.6625.

[45]  D. Stam,et al.  The influence of forward-scattered light in transmission measurements of (exo)planetary atmospheres , 2012, 1208.2795.

[46]  R. Turco,et al.  The clouds are hazes of Venus , 1983 .

[47]  Drake Deming,et al.  Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b , 2013, Nature.

[48]  Franck Selsis,et al.  3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability and habitability , 2013, 1303.7079.

[49]  Sara Seager,et al.  TOWARD THE MINIMUM INNER EDGE DISTANCE OF THE HABITABLE ZONE , 2013, 1304.3714.

[50]  Y. Yung,et al.  Atmospheric Radiation: Theoretical Basis , 1989 .

[51]  R. Luger,et al.  Extreme water loss and abiotic O2 buildup on planets throughout the habitable zones of M dwarfs. , 2014, Astrobiology.