Redox state of Earth’s magma ocean and its Venus-like early atmosphere

Sossi, Paolo A.; Burnham, Antony D.; Badro, James; Lanzirotti, A.; Newville, M.; O’Neill, Hugh St. C.

doi:10.1126/sciadv.abd1387

Cited by 109 publications

(120 citation statements)

References 102 publications

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“…This experimental setup achieved the abiotic synthesis of various amino acids from a reducing atmosphere composed of CH4, NH3, H2 and water vapor, when energy was provided by electric discharge to simulate lightnings. Even though early Earth's atmosphere, according to more recent data, might have looked different to the one simulated in the Miller-Urey experiment [11], these experiments provided first proof that complex organic molecules can arise abiotically. In the following, other groups have achieved the chemical synthesis of additional amino acids, as well as nucleotides and lipid precursors [12][13][14][15] (see [16] for a review).…”

Section: The Rna Worldmentioning

confidence: 89%

Genome Evolution from Random Ligation of RNAs of Autocatalytic Sets

Bröcker¹

2021

Preprint

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The evolutionary origin of the genome remains elusive. Here, I hypothesize that its first iteration, the protogenome, was a multi-ribozyme RNA. It evolved, likely within liposomes (the protocells) forming in dry-wet cycling environments, through the random fusion of ribozymes by a ligase and was amplified by a polymerase. The protogenome thereby linked, in one molecule, the information required to seed the protometabolism (a combination of RNA-based autocatalytic sets) in newly forming protocells. If this combination of autocatalytic sets was evolutionarily advantageous, the protogenome would have amplified in a population of multiplying protocells. It likely was a quasispecies with redundant information, e.g., multiple copies of one ribozyme. As such, new functionalities could evolve, including a genetic code. Once one or more components of the protometabolism were templated by the protogenome (e.g., when a ribozyme was replaced by a protein enzyme), and/or addiction modules evolved, the protometabolism became dependent on the protogenome. Along with increasing fidelity of the RNA polymerase, the protogenome could grow, e.g., by incorporating additional ribozyme domains. Finally, the protogenome could have evolved into a DNA genome with increased stability and storage capacity. I will provide suggestions for experiments to test some aspects of this hypothesis.

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Section: The Rna Worldmentioning

confidence: 89%

Genome Evolution from Random Ligation of RNAs of Autocatalytic Sets

Bröcker¹

2021

Preprint

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“…The continents did not form until about 3 billion years ago, long after there was life and they were made of rocks that are very low in silicate content (mafic) meaning that they were particularly prone to generate H 2 via serpentinization [123,124]. The atmosphere was like that of Venus, mainly CO 2 and N 2 [29], meaning that the interface of H 2 -producing vents with a CO 2 -containing atmosphere and ocean would have generated sites with a good fit to the H 2 -producing hydrothermal vent idea.…”

Section: Discussionmentioning

confidence: 99%

“…Fascination with RNA has, however, distracted from the more important and still unanswered question of whether an RNA world ever existed and if it existed [26,27], whether it had anything to do with the origin of things that are actually alive-microbial cells [28]-notwithstanding the sobering observation that RNA, given inorganic substrates, is clearly no more alive than an isolated protein, a fat droplet, or a grain of starch. A critic will immediately interject that we are constraining the issue too much by imposing the criterion of living from "inorganic substrates", but if we accept the evidence indicating that the moon forming impact converted the Earth to a ball of boiling magma, converting all carbon to CO 2 , then CO 2 was the initial form of carbon from which life emerged [29]. Another critic will complain that after the magma oceans cooled, there was a late heavy bombardment that brought a veneer of new organics from space, countering the CO 2 dictum [30].…”

Section: Narratives Are Set In Placesmentioning

confidence: 99%

“…That is, a set of (geochemically quite questionable) Earth conditions are proposed based on the need for their existence in order to accommodate RNA synthesis for the RNA world, creating a curious kind of cart (RNA) and horse (Earth) problem. The early Earth conditions that geochemists infer are not in the slightest conducive to the specific synthesis of RNA bases [29,96] requiring a different early Earth than the one that geochemists have to offer for the RNA world to work. Some researchers question the need for an independent replicator at any point in prebiotic evolution [97,98].…”

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confidence: 99%

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To What Inanimate Matter Are We Most Closely Related and Does the Origin of Life Harbor Meaning?

2021

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The question concerning the meaning of life is important, but it immediately confronts the present authors with insurmountable obstacles from a philosophical standpoint, as it would require us to define not only what we hold to be life, but what we hold to be meaning in addition, requiring us to do both in a properly researched context. We unconditionally surrender to that challenge. Instead, we offer a vernacular, armchair approach to life’s origin and meaning, with some layman’s thoughts on the meaning of origins as viewed from the biologist’s standpoint. One can observe that biologists generally approach the concept of biological meaning in the context of evolution. This is the basis for the broad resonance behind Dobzhansky’s appraisal that “Nothing in biology makes sense except in the light of evolution”. Biologists try to understand living things in the historical context of how they arose, without giving much thought to the definition of what life or living things are, which for a biologist is usually not an interesting question in the practical context of daily dealings with organisms. Do humans generally understand life’s meaning in the context of history? If we consider the problem of life’s origin, the question of what constitutes a living thing becomes somewhat more acute for the biologist, though not more answerable, because it is inescapable that there was a time when there were no organisms on Earth, followed by a time when there were, the latter time having persisted in continuity to the present. This raises the question of where, in that transition, chemicals on Earth became alive, requiring, in turn, a set of premises for how life arose in order to conceptualize the problem in relation to organisms we know today, including ourselves, which brings us to the point of this paper: In the same way that cultural narratives for origins always start with a setting, scientific narratives for origins also always start with a setting, a place on Earth or elsewhere where we can imagine what happened for the sake of structuring both the problem and the narrative for its solution. This raises the question of whether scientific origins settings convey meaning to humans in that they suggest to us from what kind of place and what kinds of chemicals we are descended, that is, to which inanimate things we are most closely related.

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“…The reasoning goes that as the olivine-rich mantle is subjected to pressures beyond ~21 GPa in the lower mantle, it tends to metamorphose to perovskite, a mineral that requires a 3 + valence metal, normally aluminum. However, as the concentrations of Al 3+ in the mantle are too low to meet this entire need, iron in the olivine disproportionates, with Fe 3+ deputizing for the lacking Al 3+ , while the native iron Fe 0 tends to gravitate to the core [ 61 , 62 , 63 , 85 ]. The result is a relatively oxidized volatisphere comprising CO 2 > H 2 O >> N 2 [ 85 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 ].…”

Section: The “Pond” In the Hellish Hadeanmentioning

confidence: 99%

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Russell

2021

Life

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The assumption that there was a “water problem” at the emergence of life—that the Hadean Ocean was simply too wet and salty for life to have emerged in it—is here subjected to geological and experimental “reality checks”. The “warm little pond” that would take the place of the submarine alkaline vent theory (AVT), as recently extolled in the journal Nature, flies in the face of decades of geological, microbiological and evolutionary research and reasoning. To the present author, the evidence refuting the warm little pond scheme is overwhelming given the facts that (i) the early Earth was a water world, (ii) its all-enveloping ocean was never less than 4 km deep, (iii) there were no figurative “Icelands” or “Hawaiis”, nor even an “Ontong Java” then because (iv) the solidifying magma ocean beneath was still too mushy to support such salient loadings on the oceanic crust. In place of the supposed warm little pond, we offer a well-protected mineral mound precipitated at a submarine alkaline vent as life’s womb: in place of lipid membranes, we suggest peptides; we replace poisonous cyanide with ammonium and hydrazine; instead of deleterious radiation we have the appropriate life-giving redox and pH disequilibria; and in place of messy chemistry we offer the potential for life’s emergence from the simplest of geochemically available molecules and ions focused at a submarine alkaline vent in the Hadean—specifically within the nano-confined flexible and redox active interlayer walls of the mixed-valent double layer oxyhydroxide mineral, fougerite/green rust comprising much of that mound.

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Redox state of Earth’s magma ocean and its Venus-like early atmosphere

Cited by 109 publications

References 102 publications

Genome Evolution from Random Ligation of RNAs of Autocatalytic Sets

Genome Evolution from Random Ligation of RNAs of Autocatalytic Sets

To What Inanimate Matter Are We Most Closely Related and Does the Origin of Life Harbor Meaning?

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

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