Complex Brines and Their Implications for Habitability

There is evidence that life on Earth originated in cold saline waters around scorching hydrothermal vents, and that similar conditions might exist or have existed on Mars, Europa, Ganymede, Enceladus, and other worlds. Could potentially habitable complex brines with extremely low freezing temperatures exist in the shallow subsurface of these frigid worlds? Earth, Mars, and carbonaceous chondrites have similar bulk elemental abundances, but while the Earth is depleted in the most volatile elements, the Icy Worlds of the outer solar system are expected to be rich in them. The cooling of ionic solutions containing substances that likely exist in the Icy Worlds could form complex brines with the lowest eutectic temperature possible for the compounds available in them. Indeed, here, we show observational and theoretical evidence that even elements present in trace amounts in nature are concentrated by freeze–thaw cycles, and therefore contribute significantly to the formation of brine reservoirs that remain liquid throughout the year in some of the coldest places on Earth. This is interesting because the eutectic temperature of water–ammonia solutions can be as low as ~160 K, and significant fractions of the mass of the Icy Worlds are estimated to be water substance and ammonia. Thus, briny solutions with eutectic temperature of at least ~160 K could have formed where, historically, temperature have oscillated above and below ~160 K. We conclude that complex brines must exist in the shallow subsurface of Mars and the Icy Worlds, and that liquid saline water should be present where ice has existed, the temperature is above ~160 K, and evaporation and sublimation have been inhibited.

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Stochastic accretion of the Earth

10.5194/epsc2020-652 ◽

2020 ◽

Author(s):

Paolo Sossi ◽

Ingo Stotz ◽

Seth Jacobson ◽

Alessandro Morbidelli ◽

Hugh O'Neill

Keyword(s):

Building Blocks ◽

Physical Processes ◽

Volatile Elements ◽

Volatile Element ◽

Elemental Abundances ◽

Stable Isotope Fractionation ◽

The Earth ◽

Gravitational Pull ◽

Atmospheric Loss ◽

Impact Events

The Earth is depleted in volatile elements relative to chondritic meteorites, its possible building blocks. Abundances of volatile elements descend roughly log-linearly with their calculated volatilities during solar nebula condensation [1, 2]. This depletion, however, is not accompanied by any stable isotope fractionation, which would otherwise be expected during vaporisation/condensation and atmospheric loss attending accretion [3, 4]. Thus, the physical processes that led to the formation of the Earth are yet to be reconciled with its chemical composition. Here, we integrate N-body simulations of planetary formation [5] within a framework that combines estimates for the compositions of planetary building blocks with volatile element losses during collisions, to link Earth&#8217;s elemental- and isotopic make-up with accretion mechanisms. The smooth pattern of volatile depletion in the Earth reflects the stochastic accretion of numerous, smaller, partially-vaporised precursor bodies whose elemental abundances are set by the heliocentric distances at which they formed. Impact events engender vaporisation, but atmospheric loss is only efficient during the early stages of accretion when volatile species can readily escape the gravitational pull of the proto-Earth. The chemical and isotopic compositions of the most volatile elements are controlled by that of late-accreting material, during which time the proto-Earth is sufficiently large so as to limit atmospheric loss. Stable isotopes of moderately- and highly volatile elements thus retain near-chondritic compositions. [1] O&#8217;Neill and Palme (2008), Phil. Trans. R. Soc. 4205-38 [2] Braukm&#252;ller et al. (2019), Nat. Geosci., 564-9 [3] Wang and Jacobsen (2016), Nature, 521-4 [4] Sossi et al. 2018, Chem. Geol. 73-84 [5] Jacobson and Morbidelli (2014), Phil. Trans. R. Soc. 20130174

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Biological Implications of Organic Compounds in Comets

International Astronomical Union Colloquium ◽

10.1017/s0252921100109790 ◽

1989 ◽

Vol 116 (1) ◽

pp. 439-462

Author(s):

Joseph N. Marcus ◽

Margaret A. Olsen

Keyword(s):

Origin Of Life ◽

Catalytic Rna ◽

Organic Chemicals ◽

Substantial Fraction ◽

Volatile Elements ◽

The Earth ◽

The Origin Of Life ◽

Cometary Panspermia ◽

Life On Earth ◽

The Universe

AbstractOrganic chemicals — compounds that contain carbon — are the substance of life and pervade the universe. Is there a connection between comets, which are rich in prebiotic organics, and the origin of life? Current concepts of biomolecular evolution are first reviewed, including the important paradigm of catalytic RNA. At the very least, impacting comets appear to have supplied a substantial fraction of the volatile elements required for life shortly after the Earth formed. Some impacting material may even have survived chemically intact to directly provide necessary complex prebiotic organic chemicals. For life to originate and evolve in comets themselves, liquid H2O would be absolutely required: arguments for and against 26Al radiogenic melting of cometary cores are presented. Cometary panspermia, if theoretically possible, is not necessary to explain the origin of life on Earth. The Halley spacecraft provide evidence against Earth-type microorganisms in this comet’s dust.

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Factoring Origin of Life Hypotheses into the Search for Life in the Solar System and Beyond

Life ◽

10.3390/life10050052 ◽

2020 ◽

Vol 10 (5) ◽

pp. 52 ◽

Cited By ~ 4

Author(s):

Alex Longo ◽

Bruce Damer

Keyword(s):

Solar System ◽

Hydrothermal Vents ◽

Hot Springs ◽

Planetary Science ◽

Icy Moons ◽

Alternative Hypotheses ◽

Biochemical Mechanisms ◽

Early Mars ◽

Life On Earth ◽

Detection Strategies

Two widely-cited alternative hypotheses propose geological localities and biochemical mechanisms for life’s origins. The first states that chemical energy available in submarine hydrothermal vents supported the formation of organic compounds and initiated primitive metabolic pathways which became incorporated in the earliest cells; the second proposes that protocells self-assembled from exogenous and geothermally-delivered monomers in freshwater hot springs. These alternative hypotheses are relevant to the fossil record of early life on Earth, and can be factored into the search for life elsewhere in the Solar System. This review summarizes the evidence supporting and challenging these hypotheses, and considers their implications for the search for life on various habitable worlds. It will discuss the relative probability that life could have emerged in environments on early Mars, on the icy moons of Jupiter and Saturn, and also the degree to which prebiotic chemistry could have advanced on Titan. These environments will be compared to ancient and modern terrestrial analogs to assess their habitability and biopreservation potential. Origins of life approaches can guide the biosignature detection strategies of the next generation of planetary science missions, which could in turn advance one or both of the leading alternative abiogenesis hypotheses.

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Complex Autocatalysis in Simple Chemistries

Artificial Life ◽

10.1162/artl_a_00195 ◽

2016 ◽

Vol 22 (2) ◽

pp. 138-152 ◽

Cited By ~ 7

Author(s):

Nathaniel Virgo ◽

Takashi Ikegami ◽

Simon McGregor

Keyword(s):

Network Structure ◽

Exponential Growth ◽

Origins Of Life ◽

Higher Order ◽

Nonlinear Phenomena ◽

Direct Reaction ◽

Form Complex ◽

First Order ◽

Life On Earth ◽

Catalytic Effects

Life on Earth must originally have arisen from abiotic chemistry. Since the details of this chemistry are unknown, we wish to understand, in general, which types of chemistry can lead to complex, lifelike behavior. Here we show that even very simple chemistries in the thermodynamically reversible regime can self-organize to form complex autocatalytic cycles, with the catalytic effects emerging from the network structure. We demonstrate this with a very simple but thermodynamically reasonable artificial chemistry model. By suppressing the direct reaction from reactants to products, we obtain the simplest kind of autocatalytic cycle, resulting in exponential growth. When these simple first-order cycles are prevented from forming, the system achieves superexponential growth through more complex, higher-order autocatalytic cycles. This leads to nonlinear phenomena such as oscillations and bistability, the latter of which is of particular interest regarding the origins of life.

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Environmentally Responsible Behaviour for a Sustainable Future

BSSS Journal of Education ◽

10.51767/je1002 ◽

2021 ◽

Vol 10 (1) ◽

pp. 21-27

Author(s):

Rasna Sehrawat ◽

◽

Anshu Mathur

Keyword(s):

Biological Diversity ◽

Earth Systems ◽

Responsible Behavior ◽

Environmental Deterioration ◽

The Earth ◽

Environmentally Responsible ◽

Ecological Culture ◽

The Individual ◽

Life On Earth ◽

Threat To Life

Humans are the only species on the planet Earth who do not contribute in the natural environmental cycle but has always been the exploiter of the limited resources. Tecer (2007) told that Environmental deterioration, extinction, or pollution in many vital earth systems, such as air, water, soil, forest, and biological diversity have required countries to develop policies for protecting and developing the earth and promoting global cooperation on these issues. Atasoy (2005) concluded in his study that Environmental problems have become globalized and have reached the stage where they present a threat to life on Earth. This situation has led to the review of people's relationships with nature, their attitudes and behaviors towards the environment, the duties and responsibilities assumed by the individual towards nature, and the redefinition of ecological culture and environmental awareness. It is imperative to be Environmentally Responsible in the present scenario where awareness on the effect of responsible behavior already exists in abundance through media, curriculum, and social activities.

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Prospects for metazoan life in sub-glacial Antarctic lakes: the most extreme life on Earth?

International Journal of Astrobiology ◽

10.1017/s1473550418000356 ◽

2019 ◽

Vol 18 (05) ◽

pp. 416-419 ◽

Cited By ~ 1

Author(s):

Sven Thatje ◽

Alastair Brown ◽

Claus-Dieter Hillenbrand

Keyword(s):

Hydrothermal Vents ◽

Pure Water ◽

Hydrothermal Activity ◽

Microbial Life ◽

Lake Vostok ◽

Physico Chemical ◽

Physiological Adaptations ◽

Subglacial Lakes ◽

Life On Earth ◽

Harsh Conditions

AbstractAbout 400 subglacial lakes are known from Antarctica. The question of whether life unique of subglacial lakes exists has been paramount since their discovery. Despite frequent evidence of microbial life mostly from accretion ice, subglacial lakes are characterized by physiologically hostile conditions to metazoan life, as we know it. Pure water (salinity ≤0.4–1.2%), extreme cold (−3°C), high hydrostatic pressure, areas of limited or no oxygen availability and permanent darkness altogether require physiological adaptations to these harsh conditions. The record of gene sequences including some associated with hydrothermal vents does foster the idea of metazoan life in Lake Vostok. Here, we synthesize the physico-chemical environment surrounding sub-glacial lakes and potential sites of hydrothermal activity and advocate that the physico-chemical stability found at these sites may be the most likely sites for metazoan life to exist. The unique conditions presented by Lake Vostok may also offer an outlook on life to be expected in extra-terrestrial subglacial environments, such as on Jupiter's moon Europa or Saturn's moon Enceladus.

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Towards understanding how surface life can affect interior geological processes: a non-equilibrium thermodynamics approach

Earth System Dynamics ◽

10.5194/esd-2-139-2011 ◽

2011 ◽

Vol 2 (1) ◽

pp. 139-160 ◽

Cited By ~ 16

Author(s):

J. G. Dyke ◽

F. Gans ◽

A. Kleidon

Keyword(s):

Continental Crust ◽

Oceanic Crust ◽

Mantle Convection ◽

Dynamical Models ◽

Geological Processes ◽

The Earth ◽

Uplift And Erosion ◽

Life On Earth ◽

Mantle Temperature ◽

Non Equilibrium

Abstract. Life has significantly altered the Earth's atmosphere, oceans and crust. To what extent has it also affected interior geological processes? To address this question, three models of geological processes are formulated: mantle convection, continental crust uplift and erosion and oceanic crust recycling. These processes are characterised as non-equilibrium thermodynamic systems. Their states of disequilibrium are maintained by the power generated from the dissipation of energy from the interior of the Earth. Altering the thickness of continental crust via weathering and erosion affects the upper mantle temperature which leads to changes in rates of oceanic crust recycling and consequently rates of outgassing of carbon dioxide into the atmosphere. Estimates for the power generated by various elements in the Earth system are shown. This includes, inter alia, surface life generation of 264 TW of power, much greater than those of geological processes such as mantle convection at 12 TW. This high power results from life's ability to harvest energy directly from the sun. Life need only utilise a small fraction of the generated free chemical energy for geochemical transformations at the surface, such as affecting rates of weathering and erosion of continental rocks, in order to affect interior, geological processes. Consequently when assessing the effects of life on Earth, and potentially any planet with a significant biosphere, dynamical models may be required that better capture the coupled nature of biologically-mediated surface and interior processes.

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Chemosynthesis and Chemosymbiosis in the Fossil Record: Detecting Unusual Communities Using Isotope Geochemistry

The Paleontological Society Papers ◽

10.1017/s1089332600000462 ◽

1998 ◽

Vol 4 ◽

pp. 255-285 ◽

Cited By ~ 3

Author(s):

Emily A. Cobabe

Keyword(s):

Stable Isotope ◽

Fossil Record ◽

Hydrothermal Vents ◽

Evolutionary History ◽

Isotope Geochemistry ◽

Selective Advantage ◽

Geochemical Proxies ◽

Second Tier ◽

Geologic Record ◽

Life On Earth

The exploration of chemosynthetic communities in the geologic record over the last ten years has generated a series of sedimentological, tectonic and geochemical criteria that help define a continuum of environments from hot hydrothermal vents to nearshore geothermal deposits. Many of these studies have used stable isotope geochemistry to uncover a depleted carbon signature that characterizes most fossil chemosynthetically derived deposits. Isotope geochemistry (carbon, nitrogen and sulfur) as been an important thread in the story of the discovery of modern chemosynthetic communities, as well, adding to understanding of the biogeochemistry of these ecosystems. With increasing awareness of the prominence of these communities, not just as a biological novelty, but as a fundamental component of life on Earth (and perhaps elsewhere), the drive to develop geochemical proxies for chemosynthetic taxa in the fossil record intensifies. Increased ability to recognize these communities provides access to a second tier of paleobiological questions, including ideas of evolutionary history and selective advantage.

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“A Life Worthy of Being Called Human”

Environmental Ethics ◽

10.5840/enviroethics201941439 ◽

2019 ◽

Vol 41 (4) ◽

pp. 319-332

Author(s):

Catherine Larrère ◽

Keyword(s):

Sustainable Development ◽

Human Life ◽

Environmental Ethic ◽

Future Generations ◽

Human Beings ◽

Second Stage ◽

Making Sense ◽

The Earth ◽

Life On Earth ◽

Ecological Transition

“Act so that the effects of your action are compatible with the permanence of genuine human life on Earth.” How can we understand Jonas’ “maxim”? Is it too anthropocentric to be of any interest for an environmental ethic? Is is too limited to survival to have a moral signification in a truly human ethic? One can argue first that it is not so much anti-Kantian than that it challenges the current prevailing “presentism” and obliges us to take into consideration not only future generations, but also the context in which one anticipates these future generations to be living. Therefore, we can distinguish two different interpretations of Jonas’ maxim: in a first stage, that of sustainable development, it was understood as taking into consideration not only the needs but also the rights of future generations; in a second stage, that of an Anthropocene and ecological transition, it means that making sense of humanity implies connecting human beings to the Earth and other living beings far from opposing them.

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