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PostPosted: Fri Jun 21, 2019 12:44 pm 
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Impact of Stellar Superflares on Planetary Habitability

"High-energy radiation caused by exoplanetary space weather events from planet-hosting stars can play a crucial role in conditions promoting or destroying habitability in addition to the conventional factors. In this paper, we present the first quantitative impact evaluation system of stellar flares on the habitability factors with an emphasis on the impact of Stellar Proton Events. We derive the maximum flare energy from stellar starspot sizes and examine the impacts of flare associated ionizing radiation on CO2, H2, N2+O2 --rich atmospheres of a number of well-characterized terrestrial type exoplanets. Our simulations based on the Particle and Heavy Ion Transport code System [PHITS] suggest that the estimated ground level dose for each planet in the case of terrestrial-level atmospheric pressure (1 bar) for each exoplanet does not exceed the critical dose for complex (multi-cellular) life to persist, even for the planetary surface of Proxima Centauri b, Ross-128 b and TRAPPIST-1 e. However, when we take into account the effects of the possible maximum flares from those host stars, the estimated dose reaches fatal levels at the terrestrial lowest atmospheric depth on TRAPPIST-1 e and Ross-128 b. Large fluxes of coronal XUV radiation from active stars induces high atmospheric escape rates from close-in exoplanets suggesting that the atmospheric depth can be substantially smaller than that on the Earth. In a scenario with the atmospheric thickness of 1/10 of Earth's, the radiation dose from close-in planets including Proxima Centauri b and TRAPPIST-1 e reach near fatal dose levels with annual frequency of flare occurrence from their hoststars."


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PostPosted: Wed Jul 24, 2019 1:27 pm 
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Habitability and Spectroscopic Observability of Warm M-dwarf Exoplanets Evaluated with a 3D Chemistry-Climate Model

"... Here we employ a 3D high-top chemistry-climate model (CCM) to simulate the atmospheres of synchronously-rotating planets orbiting at the inner edge of habitable zones of K- and M-dwarf stars (between Teff= 2600 K and 4000 K). While our IHZ climate predictions are in good agreement with GCM studies, we find noteworthy departures in simulated ozone and HOx photochemistry. For instance, climates around inactive stars do not typically enter the classical moist greenhouse regime even with high (>10−3 mol mol−1) stratospheric water vapor mixing ratios, which suggests that planets around inactive M-stars may only experience minor water-loss over geologically significant timescales. In addition, we find much thinner ozone layers on potentially habitable moist greenhouse atmospheres, as ozone experiences rapid destruction via reaction with hydrogen oxide radicals...."


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PostPosted: Fri Jul 26, 2019 1:22 pm 
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The Bio-habitable Zone and atmospheric properties for Planets of Red Dwarfs

"... In particular, it is argued that life clement environments may be possible on tidally locked and synchronously orbiting planets of [Red Dwarfs] and K-type stars, with conditions supporting Oxygenic Photosynthesis, which on Earth was a key to Complex life. Different climate projections and the biological significance of tidal locking on putative complex life are reviewed. We show that when the effect of continuous radiation is taken into account, the Photo-synthetically Active Radiation (PAR) available on tidally locked planets, even of RDs, could produce a high Potential Plant Productivity, in analogy to mid-summer growth at high latitudes on Earth...."


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PostPosted: Wed Sep 04, 2019 12:48 pm 
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Geoscience for understanding habitability in the solar system and beyond

"This paper reviews habitability conditions for a terrestrial planet from the point of view of geosciences...."


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PostPosted: Mon Sep 09, 2019 12:48 pm 
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Oceanographic Constraints on Exoplanet Life

"... Our results suggest that planets that rotate slower and have higher surface pressure than Earth may be attractive targets for remote life detection because upwelling is enhanced on these planets. Seasonal deepening of the mixed layer on high obliquity planets may also enhance nutrient return from depth into the surface mixed layer. Efficient nutrient recycling favors greater biological activity, more biosignature production, and more detectable life. We also find that an absence of continents may be problematic for sustaining a globally active, remotely detectable ocean biosphere due to limited nutrient fluxes from coastal upwelling and continental weathering...."


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PostPosted: Wed Sep 11, 2019 12:56 pm 
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The Climates of Other Worlds: A Review of the Emerging Field of Exoplanet Climatology

"... This review summarizes the origins and evolution of the burgeoning field of exoplanet climatology, discusses recent work using a hierarchy of computer models to identify those planets most capable of supporting life, and offers a glimpse into future directions of this quickly evolving subfield of exoplanet science."


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PostPosted: Thu Sep 26, 2019 1:27 pm 
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Prospects for Life on Temperate Planets Around Brown Dwarfs

"... we find that it is unlikely for brown dwarfs with masses ≲30MJ to host habitable planets over geologically significant timescales...."


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PostPosted: Thu Sep 26, 2019 1:30 pm 
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More setting-building than worldbuilding, but:

What if Planet 9 is a Primordial Black Hole?

"We highlight that the anomalous orbits of Trans-Neptunian Objects (TNOs) and an excess in microlensing events in the 5-year OGLE dataset can be simultaneously explained by a new population of astrophysical bodies with mass several times that of Earth (M⊕). We take these objects to be primordial black holes (PBHs) and point out the orbits of TNOs would be altered if one of these PBHs was captured by the Solar System, inline with the Planet 9 hypothesis. ..."

Also amusing:

"Comments: 7 pages, 1 exact scale illustration of a 5 Earth mass black hole"


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PostPosted: Tue Oct 08, 2019 12:40 pm 
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Climate Diversity in the Habitable Zone due to Varying pN2 Levels

"... We use PlaSim, a fast 3D climate model, to simulate many hundreds of climates with varying N2 partial pressures, insolations, and surface characteristics to identify the impact of the background gas partial pressure on the climate. We find that the climate's response is nonlinear and highly sensitive to the background gas partial pressure. ..."


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PostPosted: Tue Oct 15, 2019 12:45 pm 
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No Snowball on Habitable Tidally Locked Planets with a Dynamic Ocean

"... In this paper, we use a coupled ocean-atmosphere GCM (ROCKE-3D) to model tidally locked planets with no continents. ... We show that including ocean heat transport does not reintroduce the snowball bifurcation. An implication of this result is that a tidally locked planet in the habitable zone is unlikely to be found in a snowball state for a geologically significant period of time."


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