Atmospheric Evolution

Goldblatt, Colin

doi:10.1007/978-3-319-39312-4_107

Cited by 2 publications

(4 citation statements)

References 101 publications

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“…On Earth (Marty and Dauphas 2003), it is thought to be approximately in balance between sources (half volcanic outgassing and half oxidative weathering) and the sink (burial with a touch of subducted flux). In the past, though, nitrogen fluxes are likely to have significantly changed (Goldblatt 2018). This possibly affected surface pressure, despite variations that are much lower than those expected on Venus for CO 2 , for instance.…”

Section: Linking Possible Past Habitable States To Present-day Observ...mentioning

confidence: 98%

“…For example, some results suggest maximum atmosphere pressures of about 0.5 bar on Earth (probably much less), 2.7 Gyr ago, using barometric calculations from fossilized raindrops and gas bubbles in basaltic lava (Som et al 2012(Som et al , 2016. However, the past N 2 abundance in the atmosphere is still poorly constrained and generally thought to have possibly varied by a factor 2-3 relative to present-day (Goldblatt et al 2009;Johnson and Goldblatt 2015;Goldblatt 2018). In such a scenario, considerable build-up of nitrogen in the atmosphere of Earth over its history may be expected.…”

Section: Linking Possible Past Habitable States To Present-day Observ...mentioning

confidence: 99%

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The Habitability of Venus

et al. 2023

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Venus today is inhospitable at the surface, its average temperature of 750 K being incompatible to the existence of life as we know it. However, the potential for past surface habitability and upper atmosphere (cloud) habitability at the present day is hotly debated, as the ongoing discussion regarding a possible phosphine signature coming from the clouds shows. We review current understanding about the evolution of Venus with special attention to scenarios where the planet may have been capable of hosting microbial life. We compare the possibility of past habitability on Venus to the case of Earth by reviewing the various hypotheses put forth concerning the origin of habitable conditions and the emergence and evolution of plate tectonics on both planets. Life emerged on Earth during the Hadean when the planet was dominated by higher mantle temperatures (by about $200~^{\circ}\text{C}$ 200 ∘ C ), an uncertain tectonic regime that likely included squishy lid/plume-lid and plate tectonics, and proto continents. Despite the lack of well-preserved crust dating from the Hadean and Paleoarchean, we attempt to review current understanding of the environmental conditions during this critical period based on zircon crystals and geochemical signatures from this period, as well as studies of younger, relatively well-preserved rocks from the Paleoarchean. For these early, primitive life forms, the tectonic regime was not critical but it became an important means of nutrient recycling, with possible consequences on the global environment in the long-term, that was essential to the continuation of habitability and the evolution of life. For early Venus, the question of stable surface water is closely related to tectonics. We discuss potential transitions between stagnant lid and (episodic) tectonics with crustal recycling, as well as consequences for volatile cycling between Venus’ interior and atmosphere. In particular, we review insights into Venus’ early climate and examine critical questions about early rotation speed, reflective clouds, and silicate weathering, and summarize implications for Venus’ long-term habitability. Finally, the state of knowledge of the Venusian clouds and the proposed detection of phosphine is covered.

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Section: Linking Possible Past Habitable States To Present-day Observ...mentioning

confidence: 98%

Section: Linking Possible Past Habitable States To Present-day Observ...mentioning

confidence: 99%

The Habitability of Venus

et al. 2023

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“…Furthermore, these experiments were conducted under standard modern atmospheric conditions, although the Archean atmosphere was enriched in CO 2 and depleted in O 2 relative to today (Fig. 1; Goldblatt, 2018). To our knowledge, the effect of these variables on nitrogen isotopic fractionation during diazotrophy has so far not been tested.…”

Section: Introductionmentioning

confidence: 99%

“…Modified from Goldblatt (2018). Information about evolutionary events are reviewed in Lyons et al (2024, in press).…”

Section: Introductionmentioning

confidence: 99%

Exploring the influence of atmospheric CO₂and O₂levels on the utility of nitrogen isotopes as proxy for biological N₂fixation

Wannicke,

Stüeken,

Bauersachs

et al. 2024

Preprint

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Biological N2fixation (BNF) can be traced to the Archean, over 3 Bya. The nitrogen isotopic fractionation composition (δ15N) of sedimentary rocks is commonly used to reconstruct the presence of diazotrophic ecosystems in the past. While δ15N has been calibrated under modern environmental conditions; it has not under Archean conditions, when atmospheric pO2was lower and pCO2was higher than today. Here we explore δ15N signatures in the laboratory under three simulated atmospheres with (i) elevated CO2and no O2, (ii) present day CO2and O2and (iii) elevated CO2and present day O2, in marine and freshwater, heterocytous cyanobacteria. Additionally, we augment our data set with literature data to examine for more generalized dependencies of δ15N during BNF across the Archaea and Bacteria, including cyanobacteria, and habitats. We find a mean ϵ-value of -1.38 ± 0.95, for all bacteria, including cyanobacteria, across all tested conditions. The expanded data set reveal correlations of isotopic fractionation of BNF with CO2concentrations, toxin production and light, although within 1 ‰. Moreover, correlation showed significant dependency of the magnitude of ϵ to species type, C/N ratios and toxin production in heterocytous cyanobacteria, albeit it within a small range (-1.44 ± 0.89). We therefore conclude that δ15N is likely robust when applied to the Archean, stressing the strong cyanobacterial bias. Interestingly, the increased fractionation (lower ϵ) observed in the toxin producing Nodularia and Nostoc spp. suggests a heretofore unknown role of toxins in modulating nitrogen isotopic signals that warrants further investigation.

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Atmospheric Evolution

Cited by 2 publications

References 101 publications

The Habitability of Venus

The Habitability of Venus

Exploring the influence of atmospheric CO₂and O₂levels on the utility of nitrogen isotopes as proxy for biological N₂fixation

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Atmospheric Evolution

Cited by 2 publications

References 101 publications

The Habitability of Venus

The Habitability of Venus

Exploring the influence of atmospheric CO2and O2levels on the utility of nitrogen isotopes as proxy for biological N2fixation

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Exploring the influence of atmospheric CO₂and O₂levels on the utility of nitrogen isotopes as proxy for biological N₂fixation