Emergence of a Habitable Planet

Zahnle, Kevin; Arndt, N. T.; Cockell, Charles S.; Halliday, Alex N.; Nisbet, E. G.; Selsis, Franck; Sleep, Norman H.

doi:10.1007/978-0-387-74288-5_3

Cited by 84 publications

(142 citation statements)

References 181 publications

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“…Biological studies have shown that the ultimate ancestor of life is a hyperthermophile, i.e., an organism that lives at, or possibly above, temperature of 80–110°C [e.g., Sleep , ]. As suggested by geological evidence, life has been present on the Earth for at least 3.5 Gyr and possibly occurred before 3.8 Gyr when ultramafic rocks may have been extensively exposed on the surface of the Earth [e.g., Nisbet and Fowler , ; Zahnle et al ., ; Sleep , ]. The interaction between ultramafic rocks and H 2 O in the early atmosphere may have initiated the prebiotic chemical conditions for the origin of life.…”

Section: Resultsmentioning

confidence: 99%

Influence of pyroxene and spinel on the kinetics of peridotite serpentinization

et al. 2017

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Hydrothermal experiments were performed at 311°C and 3.0 kbar on natural olivine and peridotite to investigate the kinetics of serpentinization. The results show that the rates of reaction strongly depend on grain sizes of solid reactants, with smaller grain sizes resulting in faster kinetics. After 27 days of reaction, the reaction extent was 99% for peridotite with grain sizes of <30 μm, and the reaction extent was 28% for grain sizes of 100–177 μm. Compared to peridotite, olivine is serpentinized at much slower rates, e.g., 5.3% of reaction extent was achieved for olivine with grain sizes of 100–177 μm after 27 days, approximately five times lower than that reached during peridotite serpentinization. Such contrasting results are due to the presence of pyroxene and spinel, an interpretation which is supported by a marked increase in reaction extents for experiments with the addition of pyroxene and spinel. The reaction extent achieved in experiments with 3 wt % spinel greatly increased to 98% after 27 days, much higher than that achieved during olivine serpentinization. These results appear to be related to pyroxene and spinel releasing Al and Cr during serpentinization. As indicated by compositions of serpentine, orthopyroxene lost ~60% of Al at a reaction extent of 59%. Influence of Al and Cr is suggested by a dramatic increase in reaction extents with the addition of Al2O3 and Cr2O3 powders. Olivine in natural geological settings is commonly associated with pyroxene and spinel; consequently, serpentinization kinetics may be much faster than previously thought.

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Section: Resultsmentioning

confidence: 99%

Influence of pyroxene and spinel on the kinetics of peridotite serpentinization

et al. 2017

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“…Considering the internal model, its 1‐D nature required simplifications, such as the effect of segregation, rotation and existence of a distinct basal magma ocean, as discussed in section 2.1 and Appendix . Moreover, other heat sources are neglected here, such as the tidal heating by the new Moon [ Zahnle et al , ] or reinjection of energy by impacts. Impacts might also affect volatile content by eroding the atmosphere [e.g., Walker , ; Ahrens , ] as well as supply volatiles [e.g., Watkins , ; O'Brien et al , ].…”

Section: Discussionmentioning

confidence: 99%

The relative influence of H₂O and CO₂ on the primitive surface conditions and evolution of rocky planets

et al. 2017

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How the volatile content influences the primordial surface conditions of terrestrial planets and, thus, their future geodynamic evolution is an important question to answer. We simulate the secular convective cooling of a 1‐D magma ocean (MO) in interaction with its outgassed atmosphere. The heat transfer in the atmosphere is computed either using the grey approximation or using a k‐correlated method. We vary the initial CO2 and H2O contents (respectively from 0.1 × 10−2 to 14 × 10−2 wt % and from 0.03 to 1.4 times the Earth Ocean current mass) and the solar distance—from 0.63 to 1.30 AU. A first rapid cooling stage, where efficient MO cooling and degassing take place, producing the atmosphere, is followed by a second quasi steady state where the heat flux balance is dominated by the solar flux. The end of the rapid cooling stage (ERCS) is reached when the mantle heat flux becomes negligible compared to the absorbed solar flux. The resulting surface conditions at ERCS, including water ocean's formation, strongly depend both on the initial volatile content and solar distance D. For D > DC, the “critical distance,” the volatile content controls water condensation and a new scaling law is derived for the water condensation limit. Although today's Venus is located beyond DC due to its high albedo, its high CO2/H2O ratio prevents any water ocean formation. Depending on the formation time of its cloud cover and resulting albedo, only 0.3 Earth ocean mass might be sufficient to form a water ocean on early Venus.

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“…It is clear that under the given experimental conditions oxalate is a better catalyzing agent than NaOH for the crystallization of saponite. The formation of saponite from a silica gel at 60°C and 1 atmospheric pressure in the presence of oxalate may mimic the conditions of surface temperature and pressure during the early Archean (Zahnle et al, 2007) as well as the near-surface conditions of planetoid parent bodies, such as carbonaceous chondrites (Glavin and Dworkin, 2009), that formed during the early stages of the Solar System (see Introduction).…”

Section: Discussionmentioning

confidence: 99%

Formation of Replicating Saponite from a Gel in the Presence of Oxalate: Implications for the Formation of Clay Minerals in Carbonaceous Chondrites and the Origin of Life

et al. 2012

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The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (n(C)=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth.

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Emergence of a Habitable Planet

Cited by 84 publications

References 181 publications

Influence of pyroxene and spinel on the kinetics of peridotite serpentinization

Influence of pyroxene and spinel on the kinetics of peridotite serpentinization

The relative influence of H₂O and CO₂ on the primitive surface conditions and evolution of rocky planets

Formation of Replicating Saponite from a Gel in the Presence of Oxalate: Implications for the Formation of Clay Minerals in Carbonaceous Chondrites and the Origin of Life

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Emergence of a Habitable Planet

Cited by 84 publications

References 181 publications

Influence of pyroxene and spinel on the kinetics of peridotite serpentinization

Influence of pyroxene and spinel on the kinetics of peridotite serpentinization

The relative influence of H2O and CO2 on the primitive surface conditions and evolution of rocky planets

Formation of Replicating Saponite from a Gel in the Presence of Oxalate: Implications for the Formation of Clay Minerals in Carbonaceous Chondrites and the Origin of Life

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The relative influence of H₂O and CO₂ on the primitive surface conditions and evolution of rocky planets