Aliphatic Organics Research Articles

Importance of additional aliphatic structures generated from in-situ oxidation in development of extra pores in activation of spring jasmine wood

Aliphatic organics are reactive components of biomass in activation, playing important roles in pore development. They could be consumed with progress of activation while introducing external O2 might create additional aliphatic structures via oxidation, probably facilitating generation of extra pores in resulting activated carbon (AC). This was investigated herein by activation of spring jasmine wood with ZnCl2 or K2C2O4 in presence of 11 % or 5 % O2 at 550 or 700 °C. The results suggested that the oxygen added diminished yield of ACO2ZnCl2 by 21.7 % and yield of ACO2K2C2O4 by 29.0 %, resulting from partial oxidation of carbonaceous organics on nascent AC. Nonetheless, O2 presence promoted pore development, increasing SBET from 1833.8 m2g-1 for ACN2-ZnCl2 to 2018.2 m2g-1 for ACO2ZnCl2. The SBET of ACO2K2C2O4 also increased by 35.6 % with presence of O2. Oxidization of nascent AC generated more oxygen-containing species that actively involved in polymerization with ZnCl2 or cracking with K2C2O4 to form more pores. Additionally, O2 presence generated smaller pores in ACO2ZnCl2 while larger ones in ACO2-K2C2O4, enhancing the latter AC for adsorption. Oxidation reactions could also form the AC with oxygen-rice surface and hydrophilic nature, which negatively affect aromatization and reduced interplanar spacing of carbon crystals in AC.

Recent replenishment of aliphatic organics on Ceres from a large subsurface reservoir.

Ceres hosts notable aliphatic-organic concentrations, ranging from approximately 5 to >30 weight % in specific surface areas. The origins and persistence of these organics are under debate due to the intense aliphatic organic signature and radiation levels in Ceres' orbit, which would typically lead to their destruction, hindering detection. To investigate this, we conducted laboratory experiments to replicate how the signature of the organic-rich regions would degrade due to radiation. Our findings indicate a fast degradation rate, implying the exposure of buried organics within the past few million years. This degradation rate, coupled with observed quantities, implies that the aliphatics must be present in substantial quantities within the shallow subsurface. Our estimates suggest an initial aliphatic abundance 2 to 30 times greater than currently observed, surpassing significantly the levels found in carbonaceous chondrites, indicating either a significant concentration or remarkable purity.

Inherent water in green pine needles and cypress leaves induces self-activation in microwave pyrolysis

The response of water to microwaves creates the possibility of activating green waste for the generation of porous biochar with inherent water. This hypothesis is verified herein through the microwave pyrolysis of green and dried pine needles and cypress leaves at 500 to 800 °C. The results indicate that the inherent water in the green samples induce steam reforming or gasification, thereby forming more gases at the expense of biochar and organics, such as light and heavy phenolics in bio-oil. The intensive gasification induced by the inherent water of green pine needles effectively promotes the pore development of biochar at 800 °C (805.9 versus 360.4 m2/g from the dried sample) and the adsorption of phenol (50.3 versus 34.8 mg/g from the dried sample). A similar result is observed for the pyrolysis of cypress leaves at 800 °C (452.1 m2/g from the green samples versus 110.8 m2/g from the dried samples). A lower temperature (i.e., 500 °C) with insufficient gasification results in no marked difference in pore development. Accelerated gasification with steam leads to the excessive removal of aliphatic organics but also introduces more oxygen in the biochar, making it more hydrophilic with a more fragmented surface. Nevertheless, potential local hot spots, if any, do not lead to the decomposition of inorganics, such as CaCO3, in the pyrolysis of green samples, while the pyrolysis of dried cypress does. The pyrolysis in in-situ infrared shows that 500 °C is required to effectively destruct hydrogen bonds in the green samples and the inherent water promotes the formation of more oxygen-containing functionalities but not aromatization.

Effects of Wind Speed on Size-Dependent Morphology and Composition of Sea Spray Aerosols.

Variable wind speeds over the ocean can have a significant impact on the formation mechanism and physical-chemical properties of sea spray aerosols (SSA), which in turn influence their climate-relevant impacts. Herein, for the first time, we investigate the effects of wind speed on size-dependent morphology and composition of individual nascent SSA generated from wind-wave interactions of natural seawater within a wind-wave channel as a function of size and their particle-to-particle variability. Filter-based thermal optical analysis, atomic force microscopy (AFM), AFM infrared spectroscopy (AFM-IR), and scanning electron microscopy (SEM) were employed in this regard. This study focuses on SSA with sizes within 0.04-1.8 μm generated at two wind speeds: 10 m/s, representing a wind lull scenario over the ocean, and 19 m/s, indicative of the wind speeds encountered in stormy conditions. Filter-based measurements revealed a reduction of the organic mass fraction as the wind speed increases. AFM imaging at 20% relative humidity of individual SSA identified six main morphologies: prism-like, rounded, core-shell, rod, rod inclusion core-shell, and aggregates. At 10 m/s, most SSA were rounded, while at 19 m/s, core-shells became predominant. Based on AFM-IR, rounded SSA at both wind speeds had similar composition, mainly composed of aliphatic and oxygenated species, whereas the shells of core-shells displayed more oxygenated organics at 19 m/s and more aliphatic organics at 10 m/s. Collectively, our observations can be attributed to the disruption of the sea surface microlayer film structure at higher wind speeds. The findings reveal a significant impact of wind speed on morphology and composition of SSA, which should be accounted for accurate assessment of their climate effects.

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO2

We present observations obtained with the Near Infrared Spectrograph on JWST of the five Jupiter Trojans that will be visited by the Lucy spacecraft—the Patroclus–Menoetius binary, Eurybates, Orus, Leucus, and Polymele. The measured 1.7–5.3 μm reflectance spectra, which provide increased wavelength coverage, spatial resolution, and signal-to-noise ratio over previous ground-based spectroscopy, reveal several distinct absorption features. We detect a broad OH band centered at 3 μm that is most prominent on the less-red objects Eurybates, Patroclus–Menoetius, and Polymele. An additional absorption feature at 3.3–3.6 μm, indicative of aliphatic organics, is systematically deeper on the red objects Orus and Leucus. The collisional fragment Eurybates is unique in displaying an absorption band at 4.25 μm that we attribute to bound or trapped CO2. Comparisons with other solar system small bodies reveal broad similarities in the 2.7–3.6 μm bands with analogous features on Centaurs, Kuiper Belt objects (KBOs), and the active asteroid 238P. In the context of recent solar system evolution models, which posit that the Trojans initially formed in the outer solar system, the significant attenuation of the 2.7–3.6 μm absorption features on Trojans relative to KBOs may be the result of secondary thermal processing of the Trojans’ surfaces at the higher temperatures of the Jupiter region. The CO2 band manifested on the surface of Eurybates suggests that CO2 may be a major constituent in the bulk composition of Trojans, but resides in the subsurface or deeper interior and is largely obscured by refractory material that formed from the thermophysical processes that were activated during their inward migration.

Investigation of interactions of nickel with pyrolytic products in pyrolysis of poplar with nickel acetate via furnace or microwave heating

Metal/biochar is an important catalyst with feature of easy recovering of metal via combustion of biochar carrier. During preparation of metal/biochar, interaction of metal with biochar affects evolution of pyrolytic products and dispersion of metal. Heating mode could influence interaction of metal with pyrolytic products. This was investigated by pyrolysis of sawdust loaded with nickel acetate at 400 or 600 °C with furnace and microwave heating, respectively. The results showed that cracking of biochar and volatiles was effectively promoted with Ni, generating more gases while reducing aliphatic organics and heavy phenolics in bio-oil. The enhanced cracking facilitated aromatization in microwave heating, forming biochar of higher thermostability and gases with more hydrogen. However, the furnace heating at 600 °C formed Ni/biochar of more developed pores than from microwave heating (409.1 versus 385.0 m2g−1). Microwave heating could induce merging of micropores on biochar, resulting in migration and aggregation of Ni. This led to lower capability for chemical adsorption of hydrogen and dispersion of nickel, further leading to inferior activity of Ni/biochar from microwave heating for hydrogenation of vanillin or furfural. The in-situ IR characterization of the pyrolysis showed the furnace heating reserved more oxygen-containing organics and aliphatic structures, promoting dispersion of nickel.

First Principles Modelling of Growth of Hybrid Organic-Inorganic Films

Hybrid organic-inorganic materials fabricated with molecular layer deposition (MLD) are a special class of materials that are attracting great interest in many economically and socially relevant technological applications due to their diphasic and tunable organic-inorganic structure. Despite the growing interest in these hybrid materials, knowledge around relevant precursor chemistries and reaction mechanisms, as well as details of many determined experimental results are unknown. Density functional theory (DFT) has proven to be a powerful tool to investigate and understand the atomic level details of the precursor chemistry and address aspects of the MLD experiments.In our work, we use first principles DFT calculations to examine key steps in the mechanism of hybrid film deposition through MLD by modelling precursor-surface and precursor-precursor reactions. We explore the growth mechanism of aluminium and titanium containing hybrid films, namely alucones and titanicones. Both materials are of high interest for passivation layers in batteries. For alucones we investigate in detail the chemistry of the MLD process between the post-trimethylaluminium (TMA) pulse methyl-terminated Al2O3 surface with aromatic compounds with hydroxy and/or amino groups as reactive groups: hydroquinone (HQ), 4-aminophenol (AP) and p-phenylenediamine (PD). Double reactions of HQ, AP and PDA with the Al2O3 surface are explored in detail to assist the interpretation of the experimental findings regarding the differences found for hybrid films grown with aromatic and aliphatic organic precursors. DFT calculations show that in contrast to aliphatic organics, an upright configuration will be present for HQ, AP and PD so that the molecules are self-assembled in an upright configuration, which leads to thicker hybrid films. We predict that aromatic molecules are the best choice for stable hybrid films and their chemistry can be manipulated without degrading stability. [1]We also investigate in detail the chemistry between the most common titanium precursors, namely titanium tetrachloride (TiCl4) and tetrakis(dimethylamido)titanium (Ti(DMA)4), and ethylene glycol (EG) and glycerol (GL) as the organic precursors for the fabrication of titanicone films. We analyse the impact of the substrate on the initial MLD reactions in titanicone film growth using three different surface models: anatase TiO2, rutile TiO2 and Al2O3. This work highlights the role of the phase of TiO2 and Ti-containing precursors in production of titanicone films and provides motivation to develop a new rutile TiO2 based hybrid film suggesting that the desired film growth, flexibility and stability can be achieved. [2][1] A. Muriqi, M. Karppinen and M. Nolan, Role of terminal groups in aromatic molecules on the growth of Al2O3-based hybrid materials, Dalton Transactions, 2021, 50, 17583-17593. doi.org/10.1039/D1DT03195C.[2] Arbresha Muriqi and Michael Nolan, “Role of Titanium and Organic Precursors in Molecular Layer Deposition of “Titanicone” Hybrid Materials”, Beilstein Journal of Nanotechnology, 2022, 13, 1240–1255. doi.org/10.3762/bjnano.13.103.

Molecular comparison of organic matter removal from shale gas flowback wastewater: Ozonation versus Fenton process

Shale gas extraction process generates a large amount of shale gas flowback wastewater (SGFW) containing refractory organic compounds, which can pose serious environmental threats if not properly treated. However, the extremely complex compositions of organics in SGFW are still unknown and their transformation pathways in O3- and •OH-dominated systems are not well recognized, which restrain the selection of treatment technology and optimization of operational parameters. The removal characteristics and reaction mechanism of dissolved organic matter (DOM) in SGFW treated by ozonation and Fenton processes were comparatively investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The results showed that both processes could degrade low-oxygen highly unsaturated and phenolic organics, polyphenolics and polycyclic aromatics, and transform them into aliphatic organics and high-oxygen highly unsaturated and phenolic organics. With increasing action of reactive oxygen species (O3 for ozonation and •OH for Fenton process), the degradation products (mainly aliphatic organics) increased during ozonation. However, in Fenton process, a wider range of DOM was removed without aliphatic organics accumulation. The degradation mechanisms of DOM during ozonation and Fenton processes included oxygen addition reactions (+3O, +H2O2, and +2O) as dominant pathways. However, ozonation showed more violent oxygenation, hydroxylation, and carboxylation, while Fenton process presented more violent chain-breaking reactions. These results revealed the selective oxidation of ozone and nonselective oxidation of •OH during SGFW treatment, and provided theoretical support for selecting SGFW treatment approaches.

Activation of sawdust with eggshells

Eggshell is a kitchen waste containing abundance of calcium carbonate. The CO2 from decomposition of calcium carbonate can be used to activate biomass to produce activated carbon (AC) to realize full utilization of eggshells. In this study, the activation of poplar sawdust with non-contact eggshells and no carrier gas in a crucible at 900ºC was performed. The results indicated that the sawdust could be activated with only a given amount of CO2 from eggshells, developing mainly micropores (92.0 %, 612.2 m2/g) and rendering the AC of the superior capability to adsorb phenol in the aqueous phase. The CO2 mainly facilitated dehydrogenation, dehydration, deoxygenation of the CO in esters/lactones intermediates, gasification, carbonization reactions, etc, reducing the yields of AC but enhancing C/O and C/H ratios and thermal stability of the AC. In addition, the eggshells facilitated cracking reactions at the temperatures for the pyrolysis of sawdust, producing more light aliphatic organics, heavier phenolics, and gaseous products. The non-contact activation without carrier gas eliminates the issue of post-treatment such as separation of AC and activating agent, which also features low operating cost and produces simultaneously CaO-rich material as a solid base catalyst.

Pyrolysis of banana peel with microwave and furnace as the heating sources: The distinct impacts on evolution of the pyrolytic products

Microwave pyrolysis features with different heating mechanisms and heat transfer directions from traditional pyrolysis with furnace heating, which might impact evolution of volatiles and nature of biochar in varied ways. This was investigated in this study by pyrolysis of wet and dried banana peel with microwave heating and furnace heating at 400 and 600 °C in a fixed-bed reactor. The results showed that microwave pyrolysis could drastically promote gasification of volatiles to form significantly more gases like H2 via dehydrogenation and CO via cracking and decarbonylation. This was especially evident in the pyrolysis of wet banana peel with abundant water as the heat transfer medium. The dominance of cracking/gasification of volatiles in microwave pyrolysis was due to the rapid heating and the minimized heat transfer limitation, which suppressed the secondary condensation and thus diminished the formation of bio-oil and biochar. Microwave pyrolysis also favored the cracking of the cellulose/hemicellulose-derived aliphatic organics via cracking but promoted the formation of phenolics via cracking of lignin in banana peel. Moreover, the excessive cracking reactions in the microwave pyrolysis led to the biochar of more excellent thermal stability, lower abundance of oxygen-containing functionalities like CO and more rugged morphology than that with furnace heating source.

Pyrolysis-reforming of cellulose over Ni/mordenite for production of hydrogen and heavier organics: The distinct impacts of Ni and mordenite on nature of coke

In-situ steam reforming of small organics in bio-oil while retainment of heavy ones may be a strategy to maximize utilization of organics in bio-oil. In this study, pyrolysis-reforming (pyro-reforming) of cellulose over Ni/mordenite is conducted at 400 to 600 °C, aiming to understand the influence of nickel and mordenite on the nature of the coke formed. The results show that pyro-reforming of cellulose can produce hydrogen through steam reforming of sugar derived aliphatics while retain anhydrate sugars and phenolics but only at 600 °C. Mordenite shows almost no activity in steam reforming but it can effectively promote the aromatization of aliphatic organics and the formation of amorphous aromatic coke. By contrast, nickel species on Ni/mordenite interfere with aromatization via promoting cracking, forming aliphatic coke at 400 or 500 °C. However, at 600 °C, main routes for coke formation shift to steam reforming over Ni/mordenite, producing carbon nanotubes with highly aromatic nature.

Steam reforming of ethanol, acetaldehyde, acetone and acetic acid: Understanding the reaction intermediates and nature of coke

The small aliphatic organics like ethanol, acetaldehyde, acetone and acetic acid are frequently used as feedstocks for hydrogen production via steam reforming. These organics have distinct functionalities, which might result in formation of different reaction intermediates and coke. This was investigated in this study with Ni/KIT-6 as a catalyst under normalized conditions. The results indicated that dehydration to ketene but not cracking was major route for dissociative adsorption of acetic acid on Ni/KIT-6 from 100 °C. Thermally stable CH and CC in alkenes, formed via dehydration of ethanol and aromatization of acetone/intermediates via bimolecular Aldol-condensation, were important precursors of coke in ethanol and acetone reforming. Although acetone strongly adsorbed on Ni/KIT-6, it did not polymerize to heavy oxygen-containing organics that were difficult to be gasified with steam. In comparison, the similar strong adsorption of acetaldehyde led to rapid polymerization even at 100 °C, forming the polymeric coke of highly aliphatic nature. The coking tendency in reforming followed the order: acetone > acetic acid > ethanol > acetaldehyde. Nevertheless, the amorphous form of coke in acetaldehyde reforming led to the rapid deactivation of Ni/KIT-6. The coke in ethanol, acetone and acetic acid reforming were mainly the catalytic type with the highly aromatic nature, high carbon crystal crystallinity, high thermal stability, high resistivity towards oxidation and the carbon nanotube morphology. Nevertheless, the varied reaction intermediates involved in reforming of these varied feedstock also formed the coke of some unique features.

Hydrothermal carbonization of sawdust with the bio-oil of same origin impacts evolution of structures of hydrochar

The high tendency towards polymerization is a bottle-neck issue in upgrading of bio-oil, which, however, is highly desirable in co-hydrothermal carbonization (HTC) of biomass with bio-oil for enhancing production of hydrochar. In this study, co-HTC of bio-oil of the same origin with poplar sawdust was conducted at 180 to 260 °C. The results showed that the HTC in a water medium containing 10% bio-oil could enhanced the yield of hydrochar by ca. 36% at 220 or 260 °C through the cross-polymerization of the sugar-derived furans and ketones/aldehydes as well as the phenolics in bio-oil with the sawdust-derived organics. Furans/sugars in bio-oil showed much more contribution to the increase of hydrochar yield than the phenolics like guaiacol. The highly reactive organics in bio-oil even could react with the crystal region of cellulose at 180 °C, and affected property of hydrochar at especially the higher temperatures by promoting deoxygenation, enhancing carbonization, eliminating polar functionalities like -OH, retaining C=O for continued polymerization, etc. The co-existence of aliphatic organics and phenolics in bio-oil renders the simultaneous formation of highly volatile fraction and aromatic structures in the hydrochar. These created the carbon-rich hydrochar with higher crystallinity, lower hydrophilicity and improved comprehensive combustion index.

Bacterial Utilisation of Aliphatic Organics: Is the Dwarf Planet Ceres Habitable?

The regolith environment and associated organic material on Ceres is analogous to environments that existed on Earth 3–4 billion years ago. This has implications not only for abiogenesis and the theory of transpermia, but it provides context for developing a framework to contrast the limits of Earth’s biosphere with extraterrestrial environments of interest. In this study, substrate utilisation by the ice-associated bacterium Colwellia hornerae was examined with respect to three aliphatic organic hydrocarbons that may be present on Ceres: dodecane, isobutyronitrile, and dioctyl-sulphide. Following inoculation into a phyllosilicate regolith spiked with a hydrocarbon (1% or 20% organic concentration wt%), cell density, electron transport activity, oxygen consumption, and the production of ATP, NADPH, and protein in C. hornerae was monitored for a period of 32 days. Microbial growth kinetics were correlated with changes in bioavailable carbon, nitrogen, and sulphur. We provide compelling evidence that C. hornerae can survive and grow by utilising isobutyronitrile and, in particular, dodecane. Cellular growth, electron transport activity, and oxygen consumption increased significantly in dodecane at 20 wt% compared to only minor growth at 1 wt%. Importantly, the reduction in total carbon, nitrogen, and sulphur observed at 20 wt% is attributed to biotic, rather than abiotic, processes. This study illustrates that short-term bacterial incubation studies using exotic substrates provide a useful indicator of habitability. We suggest that replicating the regolith environment of Ceres warrants further study and that this dwarf planet could be a valid target for future exploratory missions.

Organic Matter and Associated Minerals on the Dwarf Planet Ceres

Ceres is the largest object in the main belt and it is also the most water-rich body in the inner solar system besides the Earth. The discoveries made by the Dawn Mission revealed that the composition of Ceres includes organic material, with a component of carbon globally present and also a high quantity of localized aliphatic organics in specific areas. The inferred mineralogy of Ceres indicates the long-term activity of a large body of liquid water that produced the alteration minerals discovered on its surface, including ammonia-bearing minerals. To explain the presence of ammonium in the phyllosilicates, Ceres must have accreted organic matter, ammonia, water and carbon present in the protoplanetary formation region. It is conceivable that Ceres may have also processed and transformed its own original organic matter that could have been modified by the pervasive hydrothermal alteration. The coexistence of phyllosilicates, magnetite, carbonates, salts, organics and a high carbon content point to rock–water alteration playing an important role in promoting widespread carbon occurrence.

Hydroxylated Mg-rich Amorphous Silicates: A New Component of the 3.2 μm Absorption Band of Comet 67P/Churyumov–Gerasimenko

Abstract The VIRTIS imaging spectrometer on board Rosetta has shown that the nucleus surface of comet 67P/Churyumov–Gerasimenko (67P/CG) is characterized by a broad absorption band at around 3.2 μm. The feature is ubiquitous across the surface and its attribution to (a) specific material(s) has been challenging. In the present Letter, we report an experimental investigation showing that the interaction of hydrogen atoms with Mg-rich amorphous silicates determines the formation of hydroxyl groups. The resulting IR spectrum exhibits a broad feature around 3.2 μm similar to that of comet 67P/CG. Hapke’s radiative transfer model was employed to estimate an upper limit contribution of 65% of hydroxylated silicates to the observed cometary band intensity. The presence of a hydroxylated fraction in silicates on the cometary surface would represent an evolutionary link between primitive objects of the solar system and dust in the interstellar medium (ISM), where silicate grains can be hydroxylated after having interacted with hydrogen atoms. This link is consistent with the detection of the aliphatic organics in 67P/CG that also originate in the ISM.

Exploring the inhibition boundaries of mixed cultures of purple phototrophic bacteria for wastewater treatment in anaerobic conditions

The development of novel wastewater platforms should include the analysis of the most critical functional factors including the effects of toxic or inhibitory substances. Due to the novelty of purple phototrophic bacteria (PPB)-based wastewater treatment systems, this analysis has not been done yet in mixed cultures. In this work, various relevant chemical compounds, including aromatic (phenol, 2,4,6-trichlorophenol or 246TCP, 4-nitrophenol or 4CP, sulfathiazole) and aliphatic organics (methanol, trichlorethylene or TCE, oleic acid, ethanol, propionic acid), inorganic salts (ammonium, ClO3−, Na+), and metals (Fe3+, Fe2+, Cu2+, Zn2+, Ni2+, Al3+), as well as pH, are analyzed for their effect on mixed PPB cultures in anaerobic photoheterotrophic conditions using acetate as the model organic substrate. The most toxic substances detected were 246TCP, 4NP, Cu2+, Fe2+ and Ni2+, (Ki for activity: 23 ± 2, 97 ± 12, 3.1 ± 0.4, 13 ± 3, 13 ± 1 mg/L, and Ki (or toxicity threshold) for growth: 17 ± 2, (119), 3.5 ± 0.4, (4.8), (22.9) mg/L, respectively). Some substances inhibited the activity more than the growth (sulfathiazole, Ni2+ and Fe3+), or the growth more than the activity (TCE, 4NP and Fe2+). In addition, some organic substrates, such as phenol, ethanol and propionate, specifically inhibited the acetate uptake, being noncompetitive in the case of phenol and ethanol, and most likely competitive in the case of propionate. These findings are relevant for the wastewater treatment and resource recovery applications of the PPB technology, as well as for the upgrading of current models (Photo-Anaerobic Model). In addition, the data will open possibilities to promote the production of specific compounds (as PHA or single-cell proteins) by selectively inhibiting some parts of the PPB metabolism.

An endogenic origin of cerean organics

Localized deposits of aliphatic organic-rich material have been found on the surface of dwarf planet Ceres, and based on mineralogical context, it has been suggested that these organics formed within Ceres (De Sanctis et al., 2017). However, no obvious source and exposure mechanism can be inferred from the geological settings of the organic-rich terrains. The alternative hypothesis is that the organics were delivered from an exogenic source via impact (Pieters et al., 2018). We numerically simulate the thermal degradation of aliphatic organics delivered to Ceres during hypervelocity impacts, as well as the thermal degradation and excavation of organics from the subsurface. Our models show that exogenic delivery of aliphatic organics is inefficient, as most of the spectral signature of the organic species would be thermally degraded and diluted by mixing with target material in the ejecta blanket of a given crater. Instead, our models suggest that the formation of Ernutet crater excavated a subsurface reservoir of aliphatic organics from a depth of 3-6 km, bringing it close to the surface, where it could be subsequently exhumed by small craters and landslides, compatible with observations.

Infrared detection of aliphatic organics on a cometary nucleus

The ESA Rosetta mission has acquired unprecedented measurements of comet 67/P-Churyumov-Gerasimenko (hereafter 67P) nucleus surface, whose composition, as determined by in situ and remote sensing instruments including VIRTIS (Visible, InfraRed and Thermal Imaging Spectrometer) appears to be made by an assemblage of ices, minerals, and organic material. We performed a refined analysis of infrared observations of the nucleus of comet 67P carried out by the VIRTIS-M hyperspectral imager. We found that the overall shape of the 67P infrared spectrum is similar to that of other carbon-rich outer solar system objects suggesting a possible genetic link with them. More importantly, we are also able to confirm the complex spectral structure of the wide 2.8-3.6 micron absorption feature populated by fainter bands. Among these, we unambiguously identified the presence of aliphatic organics by their ubiquitous 3.38, 3.42 and 3.47 micron bands. This novel infrared detection of aliphatic species on a cometary surface has strong implications for the evolutionary history of the primordial solar system and give evidence that comets provide an evolutionary link between interstellar material and solar system bodies.

Interactions between Goethite and Humic Acid and the Stability of Goethite-Humic Acid Complex

Goethite-humic acid complex was prepared in a suspension containing goethite and humic acid. X-ray diffraction (XRD) results showed that the crystal structure of this complex had no obvious changes compared to pure goethite, but the peak intensity of the complex was slightly reduced. Transmission electron microscopy (TEM) images indicated that the surface of the goethite was coated by particles of humic acid. Compared to the infra-red (IR) spectra of goethite and humic acid, the anti-vibrational frequencies of COO- and the vibrational frequencies of ≡Fe-OH decreased by 20 cm-1 and 9 cm-1, respectively, while the vibrational frequencies of the associated hydroxyls increased by 10 cm-1 and the absorption band of carboxylic C-O and free hydroxyls almost disappeared. This indicates that the interactional mechanisms between goethite and humic acid include the monodentate coordination of Fe(Ⅲ) -carboxylate and hydrogen-bonds. Thermogravimetry/differential thermogravimetry (TG/DTG) analysis showed that the temperature of the weight loss peak for ≡Fe-OH in goethite and the complex were 258℃ and 276℃, respectively. This indicates that the coating of humic acid enhances the heat stability of ≡Fe-OH in goethite. Compared with humic acid, the temperature of the weight loss peak for aliphatic organics and aromatic organics in complex decreased by 60℃ and 26℃, respectively and the ratio of weight loss from aliphatic organics to aromatic organics in complex increased. This indicates that organics with a lower heat stability may be more easily adsorbed onto goethite and the affinity to goethite was higher for the aliphatic organics than for aromatic organics. After ultrasonic dispersion, the content of large particles (≥ 2 μm) decreased significantly for both goethite and humic acid, but the content and the size of large particles in the complex changed only slightly.