Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

AbstractIn the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

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On the probability of habitable planets

International Journal of Astrobiology ◽

10.1017/s1473550413000128 ◽

2013 ◽

Vol 12 (3) ◽

pp. 177-185 ◽

Cited By ~ 11

Author(s):

François Forget

Keyword(s):

Liquid Water ◽

Climate Models ◽

Climatic Conditions ◽

Point Of View ◽

Habitable Zone ◽

One Dimensional ◽

The Past ◽

Surface Liquid ◽

New Generation ◽

Global Mean

AbstractIn the past 15 years, astronomers have revealed that a significant fraction of the stars should harbour planets and that it is likely that terrestrial planets are abundant in our galaxy. Among these planets, how many are habitable, i.e. suitable for life and its evolution? These questions have been discussed for years and we are slowly making progress. Liquid water remains the key criterion for habitability. It can exist in the interior of a variety of planetary bodies, but it is usually assumed that liquid water at the surface interacting with rocks and light is necessary for emergence of a life able to modify its environment and evolve. The first key issue is thus to understand the climatic conditions allowing surface liquid water assuming a suitable atmosphere. These have been studied with global mean one-dimensional (1D) models which have defined the ‘classical habitable zone’, the range of orbital distances within which worlds can maintain liquid water on their surfaces (Kasting et al. 1993). A new generation of 3D climate models based on universal equations and tested on bodies in the solar system are now available to explore with accuracy climate regimes that could locally allow liquid water. The second key issue is now to better understand the processes which control the composition and the evolution of the atmospheres of exoplanets, and in particular the geophysical feedbacks that seem to be necessary to maintain a continuously habitable climate. From that point of view, it is not impossible that the Earth's case may be special and uncommon.

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Tidal evolution in multiple planet systems: application to Kepler-62 and Kepler-186

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314007832 ◽

2014 ◽

Vol 9 (S310) ◽

pp. 58-61

Author(s):

Emeline Bolmont ◽

Sean N. Raymond ◽

Jérémy Leconte ◽

Alexandre Correia ◽

Elisa Quintana

Keyword(s):

Liquid Water ◽

Dynamical Evolution ◽

Habitable Zone ◽

Tidal Evolution ◽

Surface Liquid

AbstractA large number of observed exoplanets are part of multiple planet systems. Most of these systems are sufficiently close-in to be tidally evolving. In such systems, there is a competition between the excitation caused by planet-planet interactions and tidal damping. Using as an example two multiple planet systems, which host planets in the surface liquid water habitable zone (HZ): Kepler-62 and Kepler-186, we show the importance and effect of both planetary and stellar tides on the dynamical evolution of planets and on the climate of the HZ planets.

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The habitable zone of Earth-mass planets around 47 UMa: results for land and water worlds

International Journal of Astrobiology ◽

10.1017/s1473550403001368 ◽

2003 ◽

Vol 2 (1) ◽

pp. 35-39 ◽

Cited By ~ 20

Author(s):

S. Franck ◽

M. Cuntz ◽

W. von Bloh ◽

C. Bounama

Keyword(s):

Surface Water ◽

System Approach ◽

Distinct Type ◽

Integrated System ◽

Habitable Zone ◽

Stable Orbit ◽

The Earth ◽

Earth Like Planets ◽

Very High

In a previous paper, we showed that Earth-type habitable planets around 47 UMa are in principle possible if a distinct set of conditions is warranted. These conditions include that the Earth-type planets have successfully formed and are orbitally stable and, in addition, that the 47 UMa star–planet system is relatively young ([lsim ]6 Gyr). We now extend this study by considering Earth-like planets with different land/ocean coverages. This study is again based on the so-called integrated system approach, which describes the photosynthetic biomass production taking into account a variety of climatological, biogeochemical and geodynamical processes. This approach implies a special characterization of the habitable zone defined for a distinct type of planet. We show that the likelihood of finding a habitable Earth-like planet on a stable orbit around 47 UMa critically depends on the percentage of the planetary land/ocean coverage. The likelihood is significantly increased for planets with a very high percentage of ocean surface (‘water worlds’).

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Future surface mass balance and surface melt in the Amundsen sector of the West Antarctic Ice Sheet

The Cryosphere ◽

10.5194/tc-15-571-2021 ◽

2021 ◽

Vol 15 (2) ◽

pp. 571-593

Author(s):

Marion Donat-Magnin ◽

Nicolas C. Jourdain ◽

Christoph Kittel ◽

Cécile Agosta ◽

Charles Amory ◽

...

Keyword(s):

Mass Balance ◽

Liquid Water ◽

Ice Sheet ◽

Surface Mass Balance ◽

Surface Mass ◽

Ice Shelves ◽

Net Production ◽

West Antarctic ◽

Surface Liquid ◽

Surface Melt

Abstract. We present projections of West Antarctic surface mass balance (SMB) and surface melt to 2080–2100 under the RCP8.5 scenario and based on a regional model at 10 km resolution. Our projections are built by adding a CMIP5 (Coupled Model Intercomparison Project Phase 5) multi-model-mean seasonal climate-change anomaly to the present-day model boundary conditions. Using an anomaly has the advantage to reduce CMIP5 model biases, and a perfect-model test reveals that our approach captures most characteristics of future changes despite a 16 %–17 % underestimation of projected SMB and melt rates. SMB over the grounded ice sheet in the sector between Getz and Abbot increases from 336 Gt yr−1 in 1989–2009 to 455 Gt yr−1 in 2080–2100, which would reduce the global sea level changing rate by 0.33 mm yr−1. Snowfall indeed increases by 7.4 % ∘C−1 to 8.9 % ∘C−1 of near-surface warming due to increasing saturation water vapour pressure in warmer conditions, reduced sea-ice concentrations, and more marine air intrusion. Ice-shelf surface melt rates increase by an order of magnitude in the 21st century mostly due to higher downward radiation from increased humidity and to reduced albedo in the presence of melting. There is a net production of surface liquid water over eastern ice shelves (Abbot, Cosgrove, and Pine Island) but not over western ice shelves (Thwaites, Crosson, Dotson, and Getz). This is explained by the evolution of the melt-to-snowfall ratio: below a threshold of 0.60 to 0.85 in our simulations, firn air is not entirely depleted by melt water, while entire depletion and net production of surface liquid water occur for higher ratios. This suggests that western ice shelves might remain unaffected by hydrofracturing for more than a century under RCP8.5, while eastern ice shelves have a high potential for hydrofracturing before the end of this century.

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Probing Intermolecular Couplings in Simulations of the Two-Dimensional Infrared Photon Echo Spectrum of Liquid Water

Springer Series in Chemical Physics - Ultrafast Phenomena XVI ◽

10.1007/978-3-540-95946-5_152 ◽

2009 ◽

pp. 469-471

Author(s):

Alexander Paarmann ◽

Tomoyuki Hayashi ◽

Shaul Mukamel ◽

R. J. Dwayne Miller

Keyword(s):

Liquid Water ◽

Photon Echo ◽

Two Dimensional ◽

Infrared Photon

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Resilient habitability of nearby exoplanet systems

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3408 ◽

2019 ◽

Vol 492 (1) ◽

pp. 352-368 ◽

Cited By ~ 2

Author(s):

Giorgi Kokaia ◽

Melvyn B Davies ◽

Alexander J Mustill

Keyword(s):

Giant Planet ◽

Planetary Systems ◽

Observational Constraints ◽

Habitable Zone ◽

Habitable Zones ◽

Test Particles ◽

Planetary Orbits ◽

Two Systems ◽

Earth Like Planets ◽

Exoplanet Systems

ABSTRACT We investigate the possibility of finding Earth-like planets in the habitable zone of 34 nearby FGK-dwarfs, each known to host one giant planet exterior to their habitable zone detected by RV. First we simulate the dynamics of the planetary systems in their present day configurations and determine the fraction of stable planetary orbits within their habitable zones. Then, we postulate that the eccentricity of the giant planet is a result of an instability in their past during which one or more other planets were ejected from the system. We simulate these scenarios and investigate whether planets orbiting in the habitable zone survive the instability. Explicitly we determine the fraction of test particles, originally found in the habitable zone, which remain in the habitable zone today. We label this fraction the resilient habitability of a system. We find that for most systems the probability of planets existing [or surviving] on stable orbits in the habitable zone becomes significantly smaller when we include a phase of instability in their history. We present a list of candidate systems with high resilient habitability for future observations. These are: HD 95872, HD 154345, HD 102843, HD 25015, GJ 328, HD 6718, and HD 150706. The known planets in the last two systems have large observational uncertainties on their eccentricities, which propagate into large uncertainties on their resilient habitability. Further observational constraints of these two eccentricities will allow us to better constrain the survivability of Earth-like planets in these systems.

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Bio-habitability and life on planets of M-G-type stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319001984 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 189-193

Author(s):

Amri Wandel

Keyword(s):

Liquid Water ◽

Organic Molecules ◽

Planetary Surface ◽

Habitable Zone ◽

Wide Range ◽

Complex Organic

AbstractThe recent detection of Earth-sized planets in the habitable zone of Proxima Centauri, Trappist-1, and many other nearby M-type stars (which consist some 75% of the stars) has led to speculations, whether liquid water and life actually exist on these planets. Defining the bio-habitable zone, where liquid water and complex organic molecules can survive on at least part of the planetary surface, we suggest that planets orbiting M-type stars may have life-supporting conditions for a wide range of atmospheric properties (Wandel2018). We extend this analysis to synchronously orbiting planets of K- and G-type stars and discuss the implications for the evolution and sustaining of life on planets of M- to G-type stars, in analogy to Earth.

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