A. Wandel

Astrophysical Journal 856, 165 Link to Article [DOI: 10.3847/1538-4357/aaae6e]
The Racah Institute of Physics, The Hebrew University of Jerusalem, 91904, Israel

The recent detection of Earth-sized planets in the habitable zone of Proxima Centauri, Trappist-1, and many other nearby M-type stars has led to speculations whether liquid water and life actually exist on these planets. To a large extent, the answer depends on their yet unknown atmospheres, which may, however, be within observational reach in the near future by JWST, ELT, and other planned telescopes. We consider the habitability of planets of M-type stars in the context of their atmospheric properties, heat transport, and irradiation. Instead of the traditional definition of the habitable zone, we define the biohabitable zone, where liquid water and complex organic molecules can survive on at least part of the planetary surface. The atmospheric impact on the temperature is quantified in terms of the heating factor (a combination of greenhouse heating, stellar irradiation, albedo, etc.) and heat redistribution (horizontal energy transport). We investigate the biohabitable domain (where planets can support surface liquid water and organics) in terms of these two factors. Our results suggest that planets orbiting M-type stars may have life-supporting temperatures, at least on part of their surface, for a wide range of atmospheric properties. We apply this analyses to Proxima Cen b and the Trappist-1 system. Finally, we discuss the implications for the search of biosignatures and demonstrate how they may be used to estimate the abundance of photosynthesis and biotic planets.

Nikolaos Georgakarakos¹, Siegfried Eggl², and Ian Dobbs-Dixon¹

Astrophysical Journal 856, 155 Link to Article [DOI: 10.3847/1538-4357/aaaf72]
¹New York University Abu Dhabi, P.O. Box 129188, Saadiyat Island, Abu Dhabi, UAE
²California Institute of Technology, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

The presence of giant planets influences potentially habitable worlds in numerous ways. Massive celestial neighbors can facilitate the formation of planetary cores and modify the influx of asteroids and comets toward Earth analogs later on. Furthermore, giant planets can indirectly change the climate of terrestrial worlds by gravitationally altering their orbits. Investigating 147 well-characterized exoplanetary systems known to date that host a main-sequence star and a giant planet, we show that the presence of “giant neighbors” can reduce a terrestrial planet’s chances to remain habitable, even if both planets have stable orbits. In a small fraction of systems, however, giant planets slightly increase the extent of habitable zones provided that the terrestrial world has a high climate inertia. In providing constraints on where giant planets cease to affect the habitable zone size in a detrimental fashion, we identify prime targets in the search for habitable worlds.

¹R.A.Masterson et al. (>10)
Space Science Reviews 214, 48 Link to Article [DOI
https://doi.org/10.1007/s11214-018-0483-8]
¹Space Systems Laboratory, Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, USA

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¹Conel M. O’D. Alexander, ²Kevin D. McKeegan, ³Kathrin Altwegg
Space Science Reviews 214, 36 Link to Article [DOI
https://doi.org/10.1007/s11214-018-0474-9]
¹Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, USA
²Department of Earth, Planetary, and Space Sciences, University of California–Los Angeles, Los Angeles, USA
³Physikalisches Institut, University of Bern, Bern, Switzerland

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¹Julia Martikainen, ¹Antti Penttilä, ^1,2Maria Gritsevich, ³Hannakaisa Lindqvist, ⁴Karri Muinonena
Journal of Quantitative Spectroscopy and Radiative Transfer 204, 144-151 Link to Article [https://doi.org/10.1016/j.jqsrt.2017.09.017]
¹Department of Physics, P.O. Box 64 (Gustaf Hällströmin katu 2a), FI-00014 University of Helsinki, Finland
²Institute of Physics and Technology, Ural Federal University, Mira str. 19, 620002 Ekaterinburg, Russia
³Finnish Meteorological Institute, Erik Palménin aukio 1, FI-00101 Helsinki, Finland
⁴Finnish Geospational Research Institute FGI, National Land Survey of Finland, Geodeetinrinne 2, FI-02430 Masala, Finland

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¹S. N. Teplyakova, ¹C. A. Lorenz, ¹M. A. Ivanova, ¹N. N. Kononkova, ¹M. O. Anosova, ¹K. M. Ryazantsev, ¹Yu. A. Kostitsyn
Geochemistry International 56, 1-13 Link to Article [DOI
https://doi.org/10.1134/S0016702918010081]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia

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¹Quentin Charbonnier, ^1,2Frédéric Moynier, ¹Julien Bouchez
Science Bulletin 63, 385-394 Link to Article [https://doi.org/10.1016/j.scib.2018.01.018]
¹Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, CNRS, UMR 7154, 1 rue Jussieu, 75238 Paris, France
²Institut Universitaire de France and Université Paris Diderot, 75231 Paris, France

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¹Yang Liu
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2018.04.010]
¹Lunar and Planetary Institute, Universities Space Research Association, Houston, TX, USA

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^1,2Arshad Ali, ²Iffat Jabeen, ¹Sobhi J. Nasir, ²Neil R. Banerjee
Geosciences 8, 15 Link to Article [doi:10.3390/geosciences8010015]
¹Earth Sciences Research Centre (ESRC), Sultan Qaboos University (SQU), Al-Khodh, Muscat 123, Oman
²Department of Earth Sciences, Western University, 1151 Richmond Street N., London, ON N6A 5B7, Canada

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^1,2Zhiyong Xiao,^1,3Zhaoxu Chenac, ¹Jiang Pua, ¹Xiao Xiao, ¹Yichen Wang, ¹Jun Huang
Geomorphology 306, 128-140 Link to Article [https://doi.org/10.1016/j.geomorph.2018.01.020]
¹Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, Hubei Province, China
²Space Science Institute, Macau University of Science and Technology, Macau, China
³College of Earth Sciences, Jilin University, Changchun, Jilin Province, China

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