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

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.

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

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen R. Lehmer ◽  
David C. Catling ◽  
Joshua Krissansen-Totton
Keyword(s):  
Liquid Water ◽  
Physicochemical Parameters ◽  
Silicate Weathering ◽  
Habitable Zone ◽  
Two Dimensional ◽  
Land Area ◽  
Incident Flux ◽  
Earth Like Planets ◽  
Surface Liquid ◽  
Log Linear

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.

scholarly journals On the probability of habitable planets

2013 ◽  
Vol 12 (3) ◽  
pp. 177-185 ◽  
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.

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

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.

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

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.

scholarly journals The subsurface habitability of small, icy exomoons

2020 ◽  
Vol 636 ◽  
pp. A50
Author(s):  
J. N. K. Y. Tjoa ◽  
M. Mueller ◽  
F. F. S. van der Tak
Keyword(s):  
Solar System ◽  
Liquid Water ◽  
Internal Heat ◽  
Phenomenological Approach ◽  
Habitable Zone ◽  
Melting Depth ◽  
Icy Moons ◽  
Subsurface Ocean ◽  
Tidal Heating ◽  
Ice Shell

Context. Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa and Enceladus, have already been shown to possess liquid water, a prerequisite for life on Earth. Aims. We intend to investigate under what thermal and orbital circumstances small, icy moons may sustain subsurface oceans and thus be “subsurface habitable”. We pay specific attention to tidal heating, which may keep a moon liquid far beyond the conservative habitable zone. Methods. We made use of a phenomenological approach to tidal heating. We computed the orbit averaged flux from both stellar and planetary (both thermal and reflected stellar) illumination. We then calculated subsurface temperatures depending on illumination and thermal conduction to the surface through the ice shell and an insulating layer of regolith. We adopted a conduction only model, ignoring volcanism and ice shell convection as an outlet for internal heat. In doing so, we determined at which depth, if any, ice melts and a subsurface ocean forms. Results. We find an analytical expression between the moon’s physical and orbital characteristics and the melting depth. Since this expression directly relates icy moon observables to the melting depth, it allows us to swiftly put an upper limit on the melting depth for any given moon. We reproduce the existence of Enceladus’ subsurface ocean; we also find that the two largest moons of Uranus (Titania and Oberon) could well sustain them. Our model predicts that Rhea does not have liquid water. Conclusions. Habitable exomoon environments may be found across an exoplanetary system, largely irrespective of the distance to the host star. Small, icy subsurface habitable moons may exist anywhere beyond the snow line. This may, in future observations, expand the search area for extraterrestrial habitable environments beyond the circumstellar habitable zone.

scholarly journals An Intercomparison of Model Simulations and VPR Estimates of the Vertical Structure of Warm Stratiform Rainfall during TWP-ICE

2008 ◽  
Vol 47 (11) ◽  
pp. 2797-2815 ◽  
Author(s):  
Olivier P. Prat ◽  
Ana P. Barros ◽  
Christopher R. Williams
Keyword(s):  
Boundary Conditions ◽  
Water Content ◽  
Liquid Water ◽  
Rain Rate ◽  
Dynamical Evolution ◽  
Droplet Size Distribution ◽  
Liquid Water Content ◽  
Rain Event ◽  
Uncertainty Estimates ◽  
Stratiform Rainfall

Abstract A model of rain shaft microphysics that solves the stochastic advection–coalescence–breakup equation in an atmospheric column was used to simulate the evolution of a stratiform rainfall event during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) in Darwin, Australia. For the first time, a dynamic simulation of the evolution of the drop spectra within a one-dimensional rain shaft is performed using realistic boundary conditions retrieved from real rain events. Droplet size distribution (DSD) retrieved from vertically pointing radar (VPR) measurements are sequentially imposed at the top of the rain shaft as boundary conditions to emulate a realistic rain event. Time series of model profiles of integral parameters such as reflectivity, rain rate, and liquid water content were subsequently compared with estimates retrieved from vertically pointing radars and Joss–Waldvogel disdrometer (JWD) observations. Results obtained are within the VPR retrieval uncertainty estimates. Besides evaluating the model’s ability to capture the dynamical evolution of the DSD within the rain shaft, a case study was conducted to assess the potential use of the model as a physically based interpolator to improve radar retrieval at low levels in the atmosphere. Numerical results showed that relative improvements on the order of 90% in the estimation of rain rate and liquid water content can be achieved close to the ground where the VPR estimates are less reliable. These findings raise important questions with regard to the importance of bin resolution and the lack of sensitivity for small raindrop size (<0.03 cm) in the interpretation of JWD data, and the implications of using disdrometer data to calibrate radar algorithms.

scholarly journals Habitability of Brown Dwarf Planets

2004 ◽  
Vol 213 ◽  
pp. 115-118 ◽  
Author(s):  
Andrey Andreeshchev ◽  
John Scalo
Keyword(s):  
Liquid Water ◽  
Semimajor Axis ◽  
Habitable Zone ◽  
Brown Dwarf ◽  
Zone Width ◽  
Dwarf Planets

The time during which the temperature of a terrestrial-like planet remains in the liquid water range during the fading of its parent brown dwarf is calculated as a function of brown dwarf mass and planetary semimajor axis using recent models for brown dwarf evolution and two criteria for habitable zone width. Durations of habitability range from 0.5–2 Gyr at a brown dwarf mass of 0.03 M⊙ to 2–10 Gyr at a brown dwarf mass of 0.07 M⊙ for planets within a few Roche radii.

scholarly journals The bio-habitable zone and atmospheric properties for planets of red dwarfs

2019 ◽  
Vol 19 (2) ◽  
pp. 126-135 ◽  
Author(s):  
A. Wandel ◽  
J. Gale
Keyword(s):  
Liquid Water ◽  
Biological Significance ◽  
Oxygenic Photosynthesis ◽  
Climate Projections ◽  
Habitable Zone ◽  
Atmospheric Conditions ◽  
Dwarf Stars ◽  
Wide Range ◽  
Cast Doubt ◽  
Detection Of Biomarkers

AbstractThe Kepler data show that habitable small planets orbiting Red Dwarf stars (RDs) are abundant, and hence might be promising targets to look at for biomarkers and life. Planets orbiting within the habitable zone of RDs are close enough to be tidally locked. Some recent works have cast doubt on the ability of planets orbiting RDs to support life. In contrast, it is shown that temperatures suitable for liquid water and even for organic molecules may exist on tidally locked planets (TLPs) of RDs for a wide range of atmospheres. We chart the surface temperature distribution as a function of the irradiation, greenhouse factor and heat circulation. The habitability boundaries and their dependence on the atmospheric properties are derived. By extending our previous analyses of TLPs, we find that tidally locked as well as synchronous (not completely locked) planets of RDs and K-type stars may support life, for a wider range of orbital distance and atmospheric conditions than previously thought. In particular, it is argued that life clement environments may be possible on tidally locked and synchronously orbiting planets of RDs 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 available on TLPs, even of RDs, could produce a high-potential plant productivity, in analogy to mid-summer growth at high latitudes on Earth. Awaiting the findings of TESS and JWST, we discuss the implications of the above arguments to the detection of biomarkers such as liquid water and oxygen, as well as to the abundance of biotic planets and life.

Sign in / Sign up

Export Citation Format

Share Document