Search NASA⌕ Search

SEARCH · Search NASA

Results for “Hydrothermal carbonization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Analyzers Measure Greenhouse Gases, Airborne Pollutants

In complete darkness, a NASA observatory waits. When an eruption of boiling water billows from a nearby crack in the ground, the observatory s sensors seek particles in the fluid, measure shifts in carbon isotopes, and analyze samples for biological signatures. NASA has landed the observatory in this remote location, far removed from air and sunlight, to find life unlike any that scientists have ever seen. It might sound like a scene from a distant planet, but this NASA mission is actually exploring an ocean floor right here on Earth. NASA established a formal exobiology program in 1960, which expanded into the present-day Astrobiology Program. The program, which celebrated its 50th anniversary in 2010, not only explores the possibility of life elsewhere in the universe, but also examines how life begins and evolves, and what the future may hold for life on Earth and other planets. Answers to these questions may be found not only by launching rockets skyward, but by sending probes in the opposite direction. Research here on Earth can revise prevailing concepts of life and biochemistry and point to the possibilities for life on other planets, as was demonstrated in December 2010, when NASA researchers discovered microbes in Mono Lake in California that subsist and reproduce using arsenic, a toxic chemical. The Mono Lake discovery may be the first of many that could reveal possible models for extraterrestrial life. One primary area of interest for NASA astrobiologists lies with the hydrothermal vents on the ocean floor. These vents expel jets of water heated and enriched with chemicals from off-gassing magma below the Earth s crust. Also potentially within the vents: microbes that, like the Mono Lake microorganisms, defy the common characteristics of life on Earth. Basically all organisms on our planet generate energy through the Krebs Cycle, explains Mike Flynn, research scientist at NASA s Ames Research Center. This metabolic process breaks down sugars for energy to fuel cellular functions. "We think this chemical process did not exist when life first formed on Earth," he says, "because it is based on oxygen being available, and there was little oxygen available on the early Earth." It is possible that there are anaerobic regions beneath the sea floor in which life forms like those early non-Krebs Cycle microbes may yet exist. To detect and potentially collect samples of life emerging from hydrothermal vents, Flynn and his colleagues created Medusa, a multi-sensor instrument designed for long-term observation of diked vents on the ocean floor. When the vents erupt, Medusa assesses indicators of life within the expelled water. If the results are positive, the observatory collects samples and detaches from the ocean floor, making the long journey to the surface for retrieval by scientists. One of the indicators Medusa measures is the ratio of carbon isotopes in the water, namely carbon-12 and carbon-13. Living organisms preferentially take up carbon-12, Flynn says, so examining the ratio of these isotopes can help to determine the source of carbon in an environment as either biological or non-biological. "On Mars, there is evidence of localized methane in the atmosphere, and that methane could come from biological sources or from geochemical ones," Flynn says. "Determining the background planetary carbon isotope ratios and then evaluating the specific carbon ratios in this methane would help to determine how it was formed." A long-duration observatory similar to Medusa could one day provide essential evidence for or against the presence of life on the Red Planet or beneath the ice-crusted oceans of Europa.

Source record↗
NASA NTRS2012

Morphological Study of Insoluble Organic Matter Residues from Primitive

Insoluble organic matter (IOM) constitutes a major proportion, 70-99%, of the total organic carbon found in primitive chondrites [1, 2]. One characteristic morphological component of IOM is nanoglobules [3, 4]. Some nanoglobules exhibit large N-15 and D enrichments relative to solar values, indicating that they likely originated in the ISM or the outskirts of the protoplanetary disk [3]. A recent study of samples from the Tagish Lake meteorite with varying levels of hydrothermal alteration suggest that nanoglobule abundance decreases with increasing hydrothermal alteration [5]. The aim of this study is to further document the morphologies of IOM from a range of primitive chondrites in order to determine any correlation of morphology with petrographic grade and chondrite class that could constrain the formation and/or alteration mechanisms.

Changela, H. G.↗
NASA NTRS1994

The Search for Carbonates on Mars

Liquid water is presently unstable at the Martian surface, where the mean atmospheric pressure is 6 mbar (due to CO2) and the winter diurnal temperature ranges from 150 K at the pole to 220 K at the equator. Liquid water is widely regarded as a basic requirement for living systems, suggesting that life as we know it is not possible in present surface environments on Mars. However, life may survive within "oases" where liquid water is present. Potential oases on Mars include subsurface hydrothermal systems or deeply buried aquifers where chemoautolithotrophic microorganisms may exist. Potential metabolic strategies for primary production in such environments on Mars (and for the microbial mediation of geologic processes!) encompass the full range presently known for subsurface environments on the Earth (e.g. sulphate reduction, methanogenesis, acetogenesis, etc).

Farmer, Jack D.↗
NASA NTRS2024

Coordinated Analysis of Phosphates in Samples From Asteroid (101955) Bennu

Asteroid (101955) Bennu is a B-type asteroid and a prime candidate for investigating the remnants of planet formation and enhancing our understanding of potential sources of crucial bio-essential elements for the early Earth. Remote observations of the surface of Bennu unveiled a terrain of boulders primarily composed of hydrated phyllosilicates, organic molecules, and carbonates. The hydrated nature of Bennu, the abundance of carbonates, and the presence of cm-scale carbonate veins provide clues to the nature of the building blocks of Bennu’s parent body and to its complex geological history. Here we present the first mineralogical, chemical, and isotopic results of analysis of phosphates in samples returned from Bennu by NASA’s OSIRIS-REx mission. We seek to test the hypothesis that heating of Bennu’s parent asteroid resulted in hydrothermal alteration in which melted ice reacted with the initial constituents.

J. J. Barnes↗
NASA NTRS2001

Importance of a martian hematite site for astrobiology

Defining locations where conditions may have been favorable for life is a key objective for the exploration of Mars. Of prime importance are sites where conditions may have been favorable for the preservation of evidence of prebiotic or biotic processes. Areas displaying significant concentrations of the mineral hematite (alpha-Fe2O3), recently identified by thermal emission spectrometry, may have significance in the search for evidence of extraterrestrial life. Since iron oxides can form as aqueous mineral precipitates, the potential exists to preserve microscopic evidence of life in iron oxide-depositing ecosystems. Terrestrial hematite deposits proposed as possible analogs for hematite deposits on Mars include massive (banded) iron formations, iron oxide hydrothermal deposits, iron-rich laterites and ferricrete soils, and rock varnish. We report the potential for long-term preservation of microfossils by iron oxide mineralization in specimens of the approximately 2,100-Ma banded iron deposit of the Gunflint Formation, Canada. Scanning and analytical electron microscopy reveals micrometer-scale rods, spheres, and filaments consisting predominantly of iron and oxygen with minor carbon. We interpret these objects as microbial cells permineralized by an iron oxide, presumably hematite. The confirmation of ancient martian microbial life in hematite deposits will require the return of samples to terrestrial laboratories. A hematite-rich deposit composed of aqueous iron oxide precipitates may thus prove to be a prime site for future sample return.

Exobiology/methods↗
NASA NTRS2012

Carbon and Hydrogen Isotope Measurements of Alcohols and Organic Acids by Online Pyroprobe-GC-IRMS

The detection of methane in the atmosphere of Mars, combined with evidence showing widespread water-rock interaction during martian history, suggests that the production of methane on Mars may be the result of mineral surface-catalyzed CO2 and or CO reduction during Fisher-Tropsch Type (FTT) reactions. A better understanding of these reaction pathways and corresponding C and H isotope fractionations is critical to deciphering the synthesis of organic compounds produced under abiotic hydrothermal conditions. Described here is a technique for the extraction and analysis of both C and H isotopes from alcohols (C1-C4) and organic acids (C1-C6). This work is meant to provide a "proof of concept" for making meaningful isotope measurements on complex mixtures of solid-phase hydrocarbons and other intermediary products produced during high-temperature and high-pressure synthesis on mineral-catalyzed surfaces. These analyses are conducted entirely "on-line" utilizing a CDS model 5000 Pyroprobe connected to a Thermo Trace GC Ultra that is interfaced with a Thermo MAT 253 isotope ratio mass spectrometer operating in continuous flow mode. Also, this technique is designed to carry a split of the GC-separated product to a DSQ II quadrupole mass spectrometer as a means of making semi-quantitative compositional measurements. Therefore, both chemical and isotopic measurements can be carried out on the same sample.

Socki, Richard A.↗
NASA NTRS2012

Sporadic Groundwater Upwelling in Deep Martian Craters: Evidence for Lacustrine Clays and Carbonates

While the surface of Mars may have had an active hydrosphere early in its history [1], it is likely that this water retreated to the subsurface early on due to loss of the magnetic field and early atmosphere [2]. This likely resulted in the formation of two distinct aqueous regimes for Mars from the Late Noachian onward: one dominated by redistribution of surface ice and occasional melting of snow/ice [3], and one dominated by groundwater activity [4]. The excavation of alteration minerals from deep in the crust by impact craters points to an active, ancient, deep hydrothermal system [5]. Putative sapping features [6] may occur where the groundwater breached the surface. Upwelling groundwater may also have played a critical role in the formation of massive, layered, cemented sediments in Sinus Meridiani [7,8], in the Valles Marineris [9], and possibly in Gale Crater [10], where the Curiosity Rover will land later this year. Understanding the past distribution, geochemistry, and significance of groundwater on Mars is critical to untangling the origins of deep alteration minerals, Hesperian sulfate deposits, and crater fill deposits at Gale Crater or in other locations.

Michalski, J. R.↗
NASA NTRS2017

Synthesis of Amino Acid Precursors with Organic Solids in Planetesimals with Liquid Water

Amino acids are important ingredients of life that would have been delivered to Earth by extraterrestrial sources, e.g., comets and meteorites. Amino acids are found in aqueously altered carbonaceous chondrites in good part in the form of precursors that release amino acids after acid hydrolysis. Meanwhile, most of the organic carbon (greater than 70 weight %) in carbonaceous chondrites exists in the form of solvent insoluble organic matter (IOM) with complex macromolecular structures. Complex macromolecular organic matter can be produced by either photolysis of interstellar ices or aqueous chemistry in planetesimals. We focused on the synthesis of amino acids during aqueous alteration, and demonstrated one-pot synthesis of a complex suite of amino acids simultaneously with IOM via hydrothermal experiments simulating the aqueous processing

Kebukawa, Y↗
NASA NTRS1999

Lipid synthesis under hydrothermal conditions by Fischer-Tropsch-type reactions

Ever since their discovery in the late 1970's, mid-ocean-ridge hydrothermal systems have received a great deal of attention as a possible site for the origin of life on Earth (and environments analogous to mid-ocean-ridge hydrothermal systems are postulated to have been sites where life could have originated or Mars and elsewhere as well). Because no modern-day terrestrial hydrothermal systems are free from the influence of organic compounds derived from biologic processes, laboratory experiments provide the best opportunity for confirmation of the potential for organic synthesis in hydrothermal systems. Here we report on the formation of lipid compounds during Fischer-Tropsch-type synthesis from aqueous solutions of formic acid or oxalic acid. Optimum synthesis occurs in stainless steel vessels by heating at 175 degrees C for 2-3 days and produces lipid compounds ranging from C2 to > C35 which consist of n-alkanols, n-alkanoic acids, n-alkenes, n-alkanes and alkanones. The precursor carbon sources used are either formic acid or oxalic acid, which disproportionate to H2, CO2 and probably CO. Both carbon sources yield the same lipid classes with essentially the same ranges of compounds. The synthesis reactions were confirmed by using 13C labeled precursor acids.

Non-NASA Center↗
NASA NTRS2014

Alteration of Basaltic Glass to Mg/Fe-Smectite under Acidic Conditions: A Potential Smectite Formation Mechanism on Mars

Phyllosilicates of the smectite group including Mg- and Fe-saponite and Fe(III)-rich nontronite have been identified on Mars. Smectites are believed to be formed under neutral to alkaline conditions that prevailed on early Mars. This hypothesis is supported by the observation of smectite and carbonate deposits in Noachian terrain on Mars. However, smectite may have formed under mildly acidic conditions. Abundant smectite formations have been detected as layered deposits hundreds of meters thick in intracrater depositional fans and plains sediments, while no large deposits of carbonates are found. Development of mildly acidic conditions at early Mars might allow formation of smectite but inhibit widespread carbonate precipitation. Little is known regarding the mechanisms of smectite formation from basaltic glass under acidic conditions. The objective of this study was to test a hypothesis that Mars-analogue basaltic glass alters to smectite minerals under acidic conditions (pH 4). The effects of Mg and Fe concentrations and temperature on smectite formation from basaltic glass were evaluated. Phyllosilicate synthesis was performed in batch reactors (Parr acid digestion vessel) under reducing hydrothermal conditions at 200 C and 100 C. Synthetic basaltic glass with a composition similar to that of the Gusev crater rock Adirondack (Ground surface APXS measurement) was used in these experiments. Basaltic glass was prepared by melting and quenching procedures. X-ray diffraction (XRD) analysis indicated that the synthesized glass was composed of olivine, magnetite and X-ray amorphous phase. Samples were prepared by mixing 250 mg Adirondack with 0.1 M acetic acid (final pH 4). In order to study influence of Mg concentration on smectite formation, experiments were performed with addition of 0, 1 and 10 mM MgCl2. After 1, 7 and 14 day incubations the solution composition was analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the altered glass and formed phyllosilicates were examined by XRD analysis. Mineralogical changes were significant in Adirondack incubated with 10 mM MgCl2 at pH 4 and heated at 200 C. X-ray diffraction analysis revealed formation of phyllosilicate during 14 day incubation (Figure 1). Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550 C. The position of 02l (4.60 A) and 060 (1.54 A) diffraction bands were indicative of trioctahedral smectite such as saponite. Analysis of solution composition demonstrated that aqueous concentration of Mg decreased from 10 mM to approx.4 mM after 7 day incubation likely due to saponite formation. Smectite also formed in Adirondack incubated with 0 mM MgCl2 at pH 4 and heated at 200 C. However, diffraction peak positions of 02l (4.52 A) and 060 (1.51 A) suggested formation of dioctahedral nontronite. The 100degC Mg and Fe(II) treated basaltic glass experiments are ongoing and results will be presented.

Peretyazhko, Tanya↗
NASA NTRSDate not supplied

INCORPORATION OF NITROGEN INTO ORGANICS PRODUCED BY FISCHER-TROPSCH TYPE CHEMISTRY

Laboratory simulations have demonstrated that hydrothermal systems have the potential to produce a range of organic compounds through Fischer-Tropsch type (FTT) chemistry. The distribution of products depends on several factors, including the abundance and composition of feedstock molecules, reaction temperature, and the physical and chemical characteristics of catalytic materials included in the reactions. The majority of studies per-formed to date have focused solely on inclusion of CO2 or CO and H2 as the carbon, oxygen and hydrogen sources, which limits the possible products to hydrocarbons, alcohols and carboxylic acids. A few studies have included nitrogen in the form of ammonia, which led to the production of amino acids and nitrogenous bases. Although these demonstrations provide compelling evidence that FTT reactions can produce compounds of interest for the origins of life, such reactions have been conducted under a very limited range of conditions and the synthetic reaction mechanisms have generally not been well-characterized. We have begun a series of laboratory experiments that will incorporate a range of precursor molecules in varying compositions to determine how these variables affect the relative amounts and speciation of life-essential elements in organic molecules produced under FTT conditions. In the present work, we focus on systems containing C, H, O and N. Reaction mixtures contained CO (~60-80 mM), 150 mM ammonium chloride, and water with a native iron catalyst, which also served as a source of H2 through the reduction of water. Three initial experiments were conducted at 110, 154 and 185 °C and heated for several days. Following the reaction, samples were analyzed by gas chromatography-mass spectrometry, direct analysis in real time mass spectrometry and liquid chromatography-mass spectrometry.

A. S. Burton↗
NASA NTRS1994

Carbonates in the Kaidun chondrite

Kaidun is a remarkable chondrite breccia fall containing lithic clasts that span a wide range of chondrite groups including C and E chondrites, as well as having clasts with characteristics not yet found in existing chondrite samples. The dominant lithology in Kaidun appears to be CR chondritic, consonant with recent O isotope data. The carbonates in Kaidun are presented as one mineralogical basis for comparing it to the other hydrated chondrites and to better understand its relative alteration history. The four polished thin sections of Kaidun studied contained a variety of lithologies that we classified into four groups -- CR, E, CM-like, and dark inclusions (DIs). DIs contain sulfide and magnetite morphologies that superficially resemble CI chondrites, and some of the previously reported CI lithologies in Kaidun may be what we term DIs. Carbonates were found in all lithologies studied. Carbonates in Kaidun are similar in composition to those in CR chondrites. Some of the DIs in Kaidun, previously characterized as CI, have carbonates similar to those in CR chondrites and are unlike those in CI or CM chondrites. Most carbonates in Kaidun and CR chondrites are calcites, some of which formed at temperatures above 250 C. Dolomite is less common and some may be metastable. Alteration temperatures in the Renazzo CR chondrite were estimated to be approximately 300 C, based on O isotope fractionation between phyllosilicates and magnetite. Temperatures of up to 450 C were proposed for the alteration of a CR-like dark inclusion in Kaidun, based on the presence of hydrothermal pentlandite veins. The alteration temperatures for Kaidun and the other CR chondrites are considerably higher than those suggested for CI or CM parent bodies.

Weisberg, M. K.↗
NASA NTRS2020

Incorporation of Nitrogen into Organics Produced by Fischer-Tropsch Type Chemistry

Laboratory simulations have demonstrated that hydrothermal systems have the potential to produce a range of organic compounds through Fischer-Tropsch type (FTT) chemistry. The distribution of products depends on several factors, including the abundance and composition of feed-stock molecules, reaction temperature, and the physical and chemical characteristics of catalytic materials included in the reactions. The majority of studies per-formed to date have focused solely on inclusion of CO2 or CO and H2 as the carbon, oxygen and hydrogen sources, which limits the possible products to hydro-carbons, alcohols and carboxylic acids. A few studies have included nitrogen in the form of ammonia, which led to the production of amino acids and nitrogenous bases; and a separate suite of studies included sulfur as sulfide minerals or H2S, which yielded products such as thiols and amino acids. Although these demonstrations provide compelling evidence that FTT reactions can produce compounds of interest for the origins of life, such reactions have been conducted under a very limited range of conditions and the synthetic reaction mechanisms have generally not been well-characterized. As a consequence, it is difficult to extrapolate these results to geologic systems or to evaluate how variations in reactant compositions would affect the distribution of products over time. We have begun a series of laboratory experiments that will incorporate a range of precursor molecules in varying compositions to determine how these variables affect the relative amounts and speciation of life-essential elements in organic molecules produced under FTT conditions. In the present work, we focus on systems containing C, H, O and N.

Burton, A. S.↗
NASA NTRS1996

Surveying Dead Trees and CO2-Induced Stressed Trees Using AVIRIS in the Long Valley Caldera

Since 1980 the Long Valley Caldera in the eastern Sierra Nevada (California) has shown signs of renewed volcanic activity. Frequent earthquakes, a re-inflation of the caldera, hydrothermal activity and gas emissions are the outer symptoms of this renewed activity. In 1990 and 1991 several areas of dying trees were found around Mammoth Mountain. The cause of the die off of the trees was first sought in the persistent drought in the preceding years. However, the trees died regardless of age and species. Farrar et al. (1995) started a soil-gas survey in 1994 in the dead-tree areas and found carbon dioxide concentrations ranging from 30 to 96% at soil depths between 30 and 60 cm. CO2 concentrations in the atmosphere are usually around 0.03% and in the soil profile CO2 levels do commonly not exceed 4 to 5%. Although not much is known about the effect of high levels of carbon dioxide in the soil profile on roots, it is most likely that the trees are dying due to oxygen deprivation: the CO2 drives the oxygen out of the soil. So far, four sites of dead trees have been mapped around Mammoth Mountain. The two largest dying trees sites are located near Horseshoe Lake and near Mammoth Mountain Main Lodge covering approximately an area of 10 and 8 ha respectively. Analysis of the gas composition regarding the He-3/He-4 ratio and the percentage biogenic carbon reveals the source of the gas: the magma body beneath the Long Valley Caldera. Until recently it was not known that volcanoes release abundant carbon dioxide from their flanks as diffuse soil emanations. As a result of the magma gas emission around Mammoth Mountain there is an excellent sequence of dead trees, stressed trees, healthy trees and bare soil surfaces. This research site provides excellent opportunities to: (1) Study the capabilities of imaging spectrometry to map stressed (and dead) pine and fir species; (2) Study methods to separate the vivid vegetation, stressed vegetation and dead vegetation from the soil background of glacial deposits and crystalline rocks. The dead tree areas are located on the flanks of Mammoth Mountain (N:37 deg 37' 45" and W:119 deg 02' 05") at an elevation between 2600 and 3000 meters. The area is covered by an open type of Montane Forest. The dominant tree species are Lodgepole Pine (Pinus contorta), the Red Fir (Abies magnifica) and the Jeffrey Pine (Pinus jeffreyi). The soil surface near Horseshoe Lake is generally fairly bright. The surface is covered by glacial deposits (till) consisting mainly of weathered granitic rocks.

deJong, Steven M.↗
NASA NTRS1997

Early Evolution of Earth's Geochemical Cycle and Biosphere: Implications for Mars Exobiology

Carbon (C) has played multiple key roles for life and its environment. C has formed organics, greenhouse gases, aquatic pH buffers, redox buffers, and magmatic constituents affecting plutonism and volcanism. These roles interacted across a network of reservoirs and processes known as the biogeochemical C cycle. Changes in the cycle over geologic time were driven by increasing solar luminosity, declining planetary heat flow, and continental and biological evolution. The early Archean C cycle was dominated by hydrothermal alteration of crustal rocks and by thermal emanations of CO2 and reduced species (eg., H2, Fe(2+) and sulfides). Bioorganic synthesis was achieved by nonphotosynthetic CO2-fixing bacteria (chemoautotrophs) and, possibly, bacteria (organotrophs) utilizing any available nonbiological organic C. Responding both to abundant solar energy and to a longterm decline in thermal sources of chemical energy and reducing power, the blaspheme first developed anoxygenic photosynthesis, then, ultimately, oxygenic photosynthesis. O2-photosynthesis played a central role in transforming the ancient environment and blaspheme to the modem world. The geochemical C cycles of early Earth and Mars were quite similar. The principal differences between the modem C cycles of these planets arose during the later evolution of their heat flows, crusts, atmospheres and, perhaps, their blasphemes.

DesMarais, David J.↗
NASA NTRS1999

Post-Viking microbiology: new approaches, new data, new insights

In the 20 years since the Viking experiments, major advances have been made in the areas of microbial systematics, microbial metabolism, microbial survival capacity, and the definition of environments on earth, suggesting that life is more versatile and tenacious than was previously appreciated. Almost all niches on earth which have available energy, and which are compatible with the chemistry of carbon-carbon bonds, are known to be inhabited by bacteria. The oldest known bacteria on earth apparently evolved soon after the formation of the planet, and are heat loving, hydrogen and/or sulfur metabolizing forms. Among the two microbial domains (kingdoms) is a great deal of metabolic diversity, with members of these forms being able to grow on almost any known energy source, organic or inorganic, and to utilize an impressive array of electron acceptors for anaerobic respiration. Both hydrothermal environments and the deep subsurface environments have been shown to support large populations of bacteria, growing on energy supplied by geothermal energy, thus isolating these ecosystems from the rest of the global biogeochemical cycles. This knowledge, coupled with new insights into the history of the solar system, allow one to speculate on possible evolution and survival of life forms on Mars.

Review↗
NASA NTRS2000

Geology and geochemistry of paleosols developed on the Hekpoort Basalt, Pretoria Group, South Africa

The Hekpoort paleosols comprise a regional paleoweathering horizon developed on 2.224 +/- 0.021 Ga basaltic andesite lavas at the top of the Hekpoort Formation of the Pretoria Group, Transvaal Supergroup, South Africa. In five separate profiles, from outcrops along road cuts near Waterval Onder and the Daspoort Tunnel and in three drill cores from the Bank Break Area (BB3, BB8, and BB14), the top of the paleosol is a sericite-rich zone. The sericite zone grades downward into a chlorite-rich zone. In core BB8 and in the road cut at the Daspoort Tunnel, we sampled the underlying or parent basaltic andesite into which the chlorite zone grades. We did not obtain samples of the parent material at Waterval Onder and in cores BB3 and BB14, but chemical analyses indicate that the chlorite and sericite zones in these profiles derive from underlying lavas similar to the ones we sampled in core BB8 and at the Daspoort Tunnel. The presence of apparent rip-up clasts of the paleosol in the overlying ironstones of the Strubenkop Formation in the cores from Bank Break makes it very unlikely that most of the alteration was a result of interactions with hydrothermal fluids. Desiccation cracks at the top of the paleosol that were filled with sand during the deposition of the overlying sediments at Waterval Onder point to a subaerial weathering origin. Very little, if any, Al, Ti, Zr, V, or Cr moved a discernible distance during weathering of any of the five profiles. The vertical distribution of Fe, Mg, Mn, Ni, and Co indicates that these elements were largely removed from the top of the soil during weathering. The overall abundance of these elements in each of the profiles indicates that a significant fraction of the complement lost from the top subsequently reprecipitated in the lower portion of the soil as constituents of an Fe2(+) -rich smectite. The loss of Fe from the top of the soil during weathering of the Hekpoort paleosols indicates that atmospheric PO2 was less than 8 x 10(-4) atm about 2.22 Ga. Fe2(+) -rich smectite should only precipitate during soil formation if atmospheric PCO2 is less than or equal to 2 x 10(-2) atm (Rye, Kuo, and Holland, 1995). Ca and Na were largely lost during weathering. Some Na was apparently added to the sericite zone in cores BB3, BB8, and BB14 after weathering. All five profiles are enriched in K and Rb, and most are enriched in Ba. The distribution of these elements indicates that they all were added during post-weathering hydrothermal metasomatism. Rb-Sr analysis of the paleosol at the Daspoort Tunnel indicates that metasomatism last affected that profile 1.925 +/- 0.032 Ga (Macfarlane and Holland, 1991).

Non-NASA Center↗
NASA NTRS2023

Surface Volatile Composition as Evidence for Hydrothermal Processes Lasting Longer in Triton’s Interior than Pluto’s

Ocean worlds, or icy bodies in the outer solar system that have or once had subsurface liquid water oceans, are among the most compelling topics of astrobiology. Typically, confirming the existence of a subsurface ocean requires close spacecraft observations. However, combining our understanding of the chemistry that takes place in a subsurface ocean with our knowledge of the building blocks that formed potential ocean worlds provides an opportunity to identify tracers of endogenic activity in the surface volatiles of Pluto and Triton. We show here that the current composition of the volatiles on the surfaces and in the atmospheres of Pluto and Triton are deficient in carbon, which can only be explained by the loss of CH4 through a combination of aqueous chemistry and atmospheric processes. Furthermore, we find that the relative nitrogen and water abundances are within the range observed in building block analogs, comets, and chondrites. A lower limit for N/Ar in Pluto's atmosphere also suggests source building blocks that have a cometary or chondritic composition, all pointing to an origin for their nitrogen as NH3 or organics. Triton's lower abundance of CH4 compared to Pluto, and the detection of CO2 at Triton but not at Pluto points to aqueous chemistry in a subsurface ocean that was more efficient at Triton than Pluto. These results have applications to other large Kuiper Belt objects as well as the assessment of formation locations and times for the four giant planets given future probe measurements of noble gas abundances and isotope ratios.

Solar system formation↗