No Snowball Cycles at the Outer Edge of the Habitable Zone for Habitable Tidally Locked Planets

Checlair, J.; Salazar, A. M.; Paradise, Adiv; Menou, Kristen; Abbot, Dorian S.

doi:10.3847/2041-8213/ab5957

Cited by 7 publications

(5 citation statements)

References 48 publications

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“…However, they will depend on the spectral type of the star, the rotational and orbital properties of the planet, and its geographical characteristics (e.g. Checlair et al, 2017Checlair et al, , 2019Foley, 2019;Paradise et al, 2019;Walsh et al, 2019;Yue & Yang, 2020), while the development and nature of a salt crust will depend on the details of the ocean composition. The abiotic origin of life is arguably the greatest unsolved scientific problem, but thus far has no standard model.…”

Section: Implications For Life On Europamentioning

confidence: 99%

Laboratory exploration of mineral precipitates from Europa's subsurface ocean

Thompson¹,

Kennedy²,

Butler³

et al. 2021

J Appl Cryst

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The precipitation of hydrated phases from a chondrite-like Na–Mg–Ca–SO4–Cl solution is studied using in situ synchrotron X-ray powder diffraction, under rapid- (360 K h−1, T = 250–80 K, t = 3 h) and ultra-slow-freezing (0.3 K day−1, T = 273–245 K, t = 242 days) conditions. The precipitation sequence under slow cooling initially follows the predictions of equilibrium thermodynamics models. However, after ∼50 days at 245 K, the formation of the highly hydrated sulfate phase Na2Mg(SO4)2·16H2O, a relatively recent discovery in the Na2Mg(SO4)2–H2O system, was observed. Rapid freezing, on the other hand, produced an assemblage of multiple phases which formed within a very short timescale (≤4 min, ΔT = 2 K) and, although remaining present throughout, varied in their relative proportions with decreasing temperature. Mirabilite and meridianiite were the major phases, with pentahydrite, epsomite, hydrohalite, gypsum, blödite, konyaite and loweite also observed. Na2Mg(SO4)2·16H2O was again found to be present and increased in proportion relative to other phases as the temperature decreased. The results are discussed in relation to possible implications for life on Europa and application to other icy ocean worlds.

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Section: Implications For Life On Europamentioning

confidence: 99%

Laboratory exploration of mineral precipitates from Europa's subsurface ocean

Thompson¹,

Kennedy²,

Butler³

et al. 2021

J Appl Cryst

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“…The most significant advance with respect to complexity in the natural history of Earth was the Cambrian Explosion, the rapid diversification of forms and functions after the last Snowball Earth Event. Checlair et al [148,149] argued that no Snowball Event could occur on a tidally locked planet; instead, it would smoothly transition from partial to complete ice coverage and back. Thus, it seems more likely that the biosphere on a tidally locked planet would remain rather simple, lessening the chances for major transitions in an evolutionary trajectory like the Cambrian Explosion that occurred on Earth.…”

Section: Life On a Tidally Locked Red Dwarf Planetmentioning

confidence: 99%

The Astrobiology of Alien Worlds: Known and Unknown Forms of Life

Irwin

Schulze‐Makuch

2020

Universe

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Most definitions of life assume that, at a minimum, life is a physical form of matter distinct from its environment at a lower state of entropy than its surroundings, using energy from the environment for internal maintenance and activity, and capable of autonomous reproduction. These assumptions cover all of life as we know it, though more exotic entities can be envisioned, including organic forms with novel biochemistries, dynamic inorganic matter, and self-replicating machines. The probability that any particular form of life will be found on another planetary body depends on the nature and history of that alien world. So the biospheres would likely be very different on a rocky planet with an ice-covered global ocean, a barren planet devoid of surface liquid, a frigid world with abundant liquid hydrocarbons, on a rogue planet independent of a host star, on a tidally locked planet, on super-Earths, or in long-lived clouds in dense atmospheres. While life at least in microbial form is probably pervasive if rare throughout the Universe, and technologically advanced life is likely much rarer, the chance that an alternative form of life, though not intelligent life, could exist and be detected within our Solar System is a distinct possibility.

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“…Rocky exoplanet climate and habitability studies that include silicate weathering invariably use the WHAK model (e.g., Kite et al 2011;Abbot et al 2012;Edson et al 2012;Watanabe et al 2014;Foley 2015;Menou 2015;Abbot 2016;Batalha et al 2016;Haqq-Misra et al 2016;Paradise & Menou 2017;Ramirez 2018;Rushby et al 2018;Checlair et al 2019b;Paradise et al 2020). However, there are orders-of-magnitude discrepancies between the weathering rates predicted by laboratory silicate dissolution experiments and the weathering rates observed in field studies of silicate weathering (Velbel 1993;Malmström et al 2000;White & Brantley 2003;Maher et al 2006).…”

mentioning

confidence: 99%

Thermodynamic and Energetic Limits on Continental Silicate Weathering Strongly Impact the Climate and Habitability of Wet, Rocky Worlds

Graham

Pierrehumbert²

2020

ApJ

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The "liquid water habitable zone" (HZ) concept is predicated on the ability of the silicate weathering feedback to stabilize climate across a wide range of instellations. However, representations of silicate weathering used in current estimates of the effective outer edge of the HZ accounts for neither the thermodynamic limit on the concentration of weathering products in runoff set by clay precipitation nor the energetic limit on precipitation set by planetary instellation. We find that when the thermodynamic limit is included in an idealized coupled climate/ weathering model, the steady-state planetary climate loses sensitivity to silicate dissolution kinetics, becoming sensitive to temperature primarily through the effect of temperature on runoff and to pCO 2 through an effect on solute concentration mediated by pH. This increases sensitivity to land fraction, CO 2 outgassing, and geological factors such as soil age and lithology, all of which are found to have a profound effect on the position of the effective outer edge of the HZ. The interplay between runoff sensitivity and the energetic limit on precipitation leads to novel warm states in the outer reaches of the HZ, owing to the decoupling of temperature and precipitation. We discuss strategies for detecting the signature of the silicate weathering feedback through exoplanet observations in light of insights derived from the revised picture of weathering.Unified Astronomy Thesaurus concepts: Habitable planets (695); Habitable zone (696); Exoplanet atmospheres (487); Exoplanet evolution (491)

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No Snowball Cycles at the Outer Edge of the Habitable Zone for Habitable Tidally Locked Planets

Cited by 7 publications

References 48 publications

Laboratory exploration of mineral precipitates from Europa's subsurface ocean

Laboratory exploration of mineral precipitates from Europa's subsurface ocean

The Astrobiology of Alien Worlds: Known and Unknown Forms of Life

Thermodynamic and Energetic Limits on Continental Silicate Weathering Strongly Impact the Climate and Habitability of Wet, Rocky Worlds

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