Spectral fingerprints of the first detectable habitable planets
Final Report Abstract
Model for the First Potentially Habitable Planets Detected by Kepler & Ocean Worlds. In the scope of the EN Research Group we modeled how ocean world could function and how their spectra would appear remotely, compared to that of planets with continents and oceans. We calculated the theoretical spectra of the first two potentially habitable planets discovered by Kepler, Kepler-62e and Kepler-62f. The press echo to the discovery of those planets (LK is co-author on the discovery paper) and the characterization of water world paper was strong, with articles running in print media as well as online from NYT, Washington Post, Spiegel, FZ to outlets like Brigitte, a popular Women’s Magazine in Germany and Austria, what shows the impact of the discovery and this work on the public. How Would Earth Look Like as a Transiting Exoplanet and How Deep Can You Probe the Atmosphere of an Earth-Like Planet Remotely? We developed a model for how our Earth would appear as a transiting planet over a wide wavelength range to inform the design of future missions and observation strategies on how to characterize another Earth. The detectable features depend strongly on what type of star another Earth would orbit. Our own planet could only be probed in transmission down to about 12km in height because of the refraction of light in a planet’s atmosphere. That is important to know because most of Earth’s water is in the lowest 10km, thus water becomes a very difficult feature to find on an Earth transiting a G-star like our Sun. If another Earths were to transit a cooler star the atmosphere can be probed down to the ground. We analyze how deep on can probe the atmosphere of another Earth to identify the best targets for follow up observations. We Modeled How a Different Star, and UV Radiation Would Influence Detectable Biosignatures and the Surface Environment on Exoplanets. This work explored how the spectra and the detectable chemical signatures in an atmosphere change depending on the host star. As an example, if our Sun were hotter, ozone would be harder to detect, if our Sun were cooler, it would be easier to detect remotely. We also focused on how UV radiation would change detectable biosignatures. Another important aspect of this work was to explore how different the UV environment on the surface of a planet would be like through a planets geological history and especially at the time when life started on the Earth – as input for biologists on what levels of UV radiation we would suspect on the surface of an Earth-like planet. Colors of Other Worlds, Detectable Surface Features and Prioritizing Detected Exoplanets for Follow Up Observations. We explored the idea how to prioritize an exoplanet for follow up observations, characterizing it based on its colors – a traditional way to characterize astronomical objects. We used a wide variety of diverse surface life to explore how it would change the color of a planet and if that would remotely be detectable. We also developed the first catalogue of reflectance spectra for a diverse range of pigmented microorganisms, including ones that were isolated from Earth’s most extreme environments. The press echo to this color catalog was very strong, ranging from several print media like the New Yorker to Scientific American, and a wide range of online media, what shows the impact of this work on the public’s imagination. We Developed the First 1d Self Consistent Convection Cloud Model to Explore Changes of Albedo and the Lower Atmosphere on Exoplanets. Clouds will influence the detectability of atmospheric signatures as well as biosignatures on exoplanets. Therefore it is crucial to develop a simple cloud model for such planets. High clouds on Earth and other planets are an inherent 3D effect, therefore they can not be modeled self-consistently without knowing a planets rotation rate, surface topography etc. But low-level convective clouds can be modeled to help us explore how they will influence a planet’s atmosphere as well as detectable features. We Also Developed 1d Models for Hot Rocky Planets as well as Mini-Neptunes to Compare the Spectra of Such Planets to Habitable Planet Spectra. Preise und Auszeichnungen für Lisa Kaltenegger: Christian Doppler Prize for Innovation in Science, Austria 2014. Simon Foundation Award “Simons Collaboration on the Origins of Life” 2013. European Commission Role Model for Women in Science and Research 2012. Prize lecture & Heinz Maier-Leibnitz Prize for Physics of Germany 2012
Publications
- Compositions of Hot Super-Earth Atmospheres: exploring Kepler Candidates, ApJL, 742, 2, article id. L19, 2011
Miguel, Y.; Kaltenegger, L.; Fegley, B., Jr.; Schaefer, L.
(See online at https://doi.org/10.1088/2041-8205/742/2/L19) - A 1D microphysical cloud model for Earth, and Earth-like exoplanets, Icarus, 221, 2, p. 603-616, 2012
Zsom, A., Kaltenegger, L., C. Goldblatt
- Colours of extreme worlds, Astrobiology 13(1):47-56, 2013
Hegde S. & Kaltenegger L.
- Spectral fingerprints of an Earth around FGK stars, Astrobiology, 13(3): 251-269, 2013
Rugheimer, S., Kaltenegger, L., et al.
- The Tranisting Earth from UV to VIS, ApJL, 772, L31, 2013
Betremeux Y, Kaltenegger L.
- Water Planets in the Habitable Zone: Atmospheric Chemistry, Observable Features, and the case of Kepler-62e and -62f, ApJL, 775, 2, L47, 5, 2013
Kaltenegger, L., Sasselov D., Rugheimer S.
(See online at https://doi.org/10.1088/2041-8205/775/2/L47) - Exploring Atmospheres of Hot Mini-Neptunes and Extrasolar Giant Planets Orbiting Different Stars with Application to HD 97658b, WASP-12b, CoRoT- 2b, XO-1b, and HD 189733b, ApJ, 780, 2, article id. 166, 13, 2014
Miguel, Y.& Kaltenegger, L.
(See online at https://doi.org/10.1088/0004-637X/780/2/166) - Impact of atmospheric refraction: How deeply can we probe exo-Earth's atmospheres during primary eclipse observations?, The Astrophysical Journal, Volume 791, Issue 1, article id. 7, 12, 2014
Betremeux Y, Kaltenegger L.
(See online at https://doi.org/10.1088/0004-637X/791/1/7) - Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life, PNAS, 112, 13, 2015
Hegde S., Paulino-Lima, I., Kent, R., Kaltenegger L, Rothschild L.
(See online at https://doi.org/10.1073/pnas.1421237112) - “UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution ApJ 806, 1, 137, 10 pp., 2015
Rugheimer, S., Segura, A., Kaltenegger, L., Sasselov, D.
(See online at https://doi.org/10.1088/0004-637X/806/1/137)
