Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes

Abstract

The environmental conditions on the Earth before 4 billion years ago are highly uncertain, largely because of the lack of a substantial rock record from this period. During this time interval, known as the Hadean, the young planet transformed from an uninhabited world to the one capable of supporting, and inhabited by the first living cells. These cells formed in a fluid environment they could not at first control, with homeostatic mechanisms developing only later. It is therefore possible that present-day organisms retain some record of the primordial fluid in which the first cells formed. Here we present new data on the elemental compositions and mineral fingerprints of both Bacteria and Archaea, using these data to constrain the environment in which life formed. The cradle solution that produced this elemental signature was saturated in barite, sphene, chalcedony, apatite, and clay minerals. The presence of these minerals, as well as other chemical features, suggests that the cradle environment of life may have been a weathering fluid interacting with dry-land silicate rocks. The specific mineral assemblage provides evidence for a moderate Hadean climate with dry and wet seasons and a lower atmospheric abundance of CO2 than is present today.

The Ladder of Life Detection

“…Potential metabolic byproducts are distributions of species that differ from those resulting solely from abiotic thermodynamic equilibrium or kinetic steady state. They include distributions of elements present at trace levels in biological matter, but which can carry essential metabolic functions at the active sites of enzymes (Novoselov et al, 2017 ), and patterns of complexity in mixtures of organics (Marshall et al, 2017 ).…”

“…Elemental abundances may be the most survivable Ladder feature ( #5 ). They are fairly generic ( #7 ; Conrad and Nealson, 2001 ; Neveu et al, 2016 ; Novoselov et al, 2017 ; Stern et al, 2017 ), as biological uses of an element hinge on its properties ( e.g., valence), even though several elements can be used to perform the same function ( e.g., V, Fe, and/or Mo for nitrogen fixation; Hoffman et al, 2014 ). However, abiotic backgrounds must be understood at relevant spatial scales to properly interpret any deviations ( #6 ; Cady et al, 2003 ; Storrie-Lombardi and Nealson, 2003 ).…”

Sulfidic Anion Concentrations on Early Earth for Surficial Origins-of-Life Chemistry

“…Consequently, it is critical to understand the range of environmental conditions available on early Earth for abiogenesis to proceed. Work over the past few decades has begun to constrain the environmental conditions that may have been available for abiogenesis, including but not limited to the past presence of liquid water, the availability of UV light at the surface, the mix of gases being outgassed to the atmosphere, the bulk pH of the ocean, and the conditions available at deep-sea hydrothermal vents (Bada et al, 1994; Farquhar et al, 2000 ; Delano, 2001 ; Holm and Charlou, 2001 ; Mojzsis et al, 2001 ; McCollom and Seewald, 2007 ; Trail et al, 2011 ; Mulkidjanian et al, 2012; Beckstead et al, 2016 ; Sojo et al, 2016; Halevy and Bachan, 2017 ; Novoselov et al, 2017 ; Ranjan and Sasselov, 2017 ).…”

The biogeochemical cycling of chlorine

“…Troposphere: mean total chlorine including anthropogenic chlorine (Montzka et al, 2011), mean chloromethane (Verhulst et al, 2013); mean modeled sodium chloride aerosol and hydrogen chloride (Wang et al, 2019); concentrations vary significantly from the mean; concentrations of HCl, ClO, and ClONO 2 are not shown but increase in the stratosphere; molar mixing ratios for gases were converted to mg/kg using a molar mass of dry air is 28.9647 g/Mol. Biomass: chloride per dry mass in bacteria (Novoselov et al, 2017); chloride and organic chlorine per dry mass in min, max, and mean in plants (Svensson et al, 2021). Soil: chloride and organic chlorine in forest and agricultural soils in Europe (Redon et al, 2011; Svensson et al, 2021); chloride and perchlorate in semiarid to hyperarid soils (Jackson et al, 2015); perchlorate is less abundant in nonarid soils.…”

“…In soils, chlorine accounts for 0.01%–0.5% of the mass of organic matter and is the most common element in organic molecules after carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorous (Oberg, 2002; Öberg, 2003; Redon et al, 2012). As the most bioavailable halogen, within living cells, chlorine can be as abundant as sulfur and is the most abundant negatively charged ion (Kirk, 2012; Milo & Phillips, 2017; Novoselov et al, 2017). Chlorine is even present in trace atmospheric gases (Keppler et al, 2005; Wang et al, 2019).…”