Insights into the nature of cometary organic matter from terrestrial analogues

2012 ◽  
Vol 11 (2) ◽  
pp. 83-92 ◽  
Author(s):  
Richard W. Court ◽  
Mark A. Sephton
Keyword(s):  
Organic Matter ◽  
Cometary Nucleus ◽  
Cometary Nuclei ◽  
Naturally Occurring ◽  
Polycyclic Aromatic ◽  
Radiation Induced ◽  
Remote Observation ◽  
Complex Organic ◽  
Cometary Comae

AbstractThe nature of cometary organic matter is of great interest to investigations involving the formation and distribution of organic matter relevant to the origin of life. We have used pyrolysis–Fourier transform infrared (FTIR) spectroscopy to investigate the chemical effects of the irradiation of naturally occurring bitumens, and to relate their products of pyrolysis to their parent assemblages. The information acquired has then been applied to the complex organic matter present in cometary nuclei and comae. Amalgamating the FTIR data presented here with data from published studies enables the inference of other comprehensive trends within hydrocarbon mixtures as they are progressively irradiated in a cometary environment, namely the polymerization of lower molecular weight compounds; an increased abundance of polycyclic aromatic hydrocarbon structures; enrichment in 13C; reduction in atomic H/C ratio; elevation of atomic O/C ratio and increase in the temperature required for thermal degradation. The dark carbonaceous surface of a cometary nucleus will display extreme levels of these features, relative to the nucleus interior, while material in the coma will reflect the degree of irradiation experienced by its source location in the nucleus. Cometary comae with high methane/water ratios indicate a nucleus enriched in methane, favouring the formation of complex organic matter via radiation-induced polymerization of simple precursors. In contrast, production of complex organic matter is hindered in a nucleus possessing a low methane/water ration, with the complex organic matter that does form possessing more oxygen-containing species, such as alcohol, carbonyl and carboxylic acid functional groups, resulting from reactions with hydroxyl radicals formed by the radiolysis of the more abundant water. These insights into the properties of complex cometary organic matter should be of particular interest to both remote observation and space missions involving in situ analyses and sample return of cometary materials.

scholarly journals Surface Morphology of Cometary Nuclei

1991 ◽  
Vol 116 (2) ◽  
pp. 761-767
Author(s):  
D. Möhlmann ◽  
E. Kührt
Keyword(s):  
Imaging Techniques ◽  
Cometary Nucleus ◽  
Complex Data ◽  
Cometary Nuclei ◽  
Precise Knowledge ◽  
New Information ◽  
Consistent Model ◽  
Topological Surface ◽  
In Situ Observations

Abstract.The first in situ observations of a cometary nucleus by imaging techniques on board the VEGA and Giotto spacecraft in 1986 opened the possibility of directly studying the properties and structures of a cometary surface. This new information, combined with results from other experiments made by these spacecraft and with results from laboratory experiments and Earth-bound radar observations, gave a better basis for coming from speculation to more precise knowledge in describing properties of cometary surfaces and related activity. It is the aim of this paper to discuss the different views developed to understand properties of cometary surfaces and to propose a consistent model for understanding topological surface properties and related cometary activity. We accomplish this by extending former hypotheses and approaches and making them more precise in the light of the new and more complex data.

scholarly journals Iron and nickel atoms in comet atmospheres

2020 ◽  
Author(s):  
Jean Manfroid ◽  
Damien Hutsemekers ◽  
Emmanuel Jehin
Keyword(s):  
Organic Molecules ◽  
Large Telescope ◽  
Cometary Nuclei ◽  
Near Ultraviolet ◽  
Very Large Telescope ◽  
Order Of Magnitude ◽  
Iron Nickel ◽  
Space Dust ◽  
Complex Organic ◽  
Cometary Comae

Abstract When sufficiently close to the Sun, ices in cometary nuclei sublimate, ejecting in space dust and gases whose compositions can be derived by the remote spectral analysis of the cometary atmospheres. Those very rich spectra reveal a host of constituents from simple radicals like OH and CN in the optical range, to relatively complex organic molecules in the infrared and sub-millimeter domain. The majority of these molecules are made of C, H, O and N atoms. Iron, nickel and a few other siderophile atoms have only been detected in two exceptional sungrazer comets in a century and a half. Here we report that free atoms of iron and nickel are ubiquitous in cometary atmospheres as revealed by high-resolution spectra obtained in the near-ultraviolet with the ESO Very Large Telescope for a large sample of comets of various dynamical origins. The emissions of NiI and FeI in cometary comae have been overlooked until now and, surprisingly, are even detected at large heliocentric distances. The abundances of both species appear to be of the same order of magnitude, contrasting with the typical solar system abundance and providing clues about their origins in comet nuclei.

scholarly journals Quantitative Transcriptomics Reveals the Growth- and Nutrient-Dependent Response of a Streamlined Marine Methylotroph to Methanol and Naturally Occurring Dissolved Organic Matter

mBio ◽  
2016 ◽  
Vol 7 (6) ◽  
Author(s):  
Scott M. Gifford ◽  
Jamie W. Becker ◽  
Oscar A. Sosa ◽  
Daniel J. Repeta ◽  
Edward F. DeLong
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Carbon Metabolism ◽  
Marine Organic Matter ◽  
Naturally Occurring ◽  
Genome Wide ◽  
Carbon Substrates ◽  
Mrna Content ◽  
Nutrient Conditions

ABSTRACT The members of the OM43 clade of Betaproteobacteria are abundant coastal methylotrophs with a range of carbon-utilizing capabilities. However, their underlying transcriptional and metabolic responses to shifting conditions or different carbon substrates remain poorly understood. We examined the transcriptional dynamics of OM43 isolate NB0046 subjected to various inorganic nutrient, vitamin, and carbon substrate regimes over different growth phases to (i) develop a quantitative model of its mRNA content; (ii) identify transcriptional markers of physiological activity, nutritional state, and carbon and energy utilization; and (iii) identify pathways involved in methanol or naturally occurring dissolved organic matter (DOM) metabolism. Quantitative transcriptomics, achieved through addition of internal RNA standards, allowed for analyses on a transcripts-per-cell scale. This streamlined bacterium exhibited substantial shifts in total mRNA content (ranging from 1,800 to 17 transcripts cell −1 in the exponential and deep stationary phases, respectively) and gene-specific transcript abundances (>1,000-fold increases in some cases), depending on the growth phase and nutrient conditions. Carbon metabolism genes exhibited substantial dynamics, including those for ribulose monophosphate, tricarboxylic acid (TCA), and proteorhodopsin, as well as methanol dehydrogenase ( xoxF ), which, while always the most abundant transcript, increased from 5 to 120 transcripts cell −1 when cultures were nutrient and vitamin amended. In the DOM treatment, upregulation of TCA cycle, methylcitrate cycle, vitamin, and organic phosphorus genes suggested a metabolic route for this complex mixture of carbon substrates. The genome-wide inventory of transcript abundances produced here provides insight into a streamlined marine bacterium’s regulation of carbon metabolism and energy flow, providing benchmarks for evaluating the activity of OM43 populations in situ . IMPORTANCE Bacteria exert a substantial influence on marine organic matter flux, yet the carbon components targeted by specific bacterial groups, as well as how those groups’ metabolic activities change under different conditions, are not well understood. Gene expression studies of model organisms can identify these responses under defined conditions, which can then be compared to environmental transcriptomes to elucidate in situ activities. This integration, however, is limited by the data’s relative nature. Here, we report the fully quantitative transcriptome of a marine bacterium, providing a genome-wide survey of cellular transcript abundances and how they change with different states of growth, nutrient conditions, and carbon substrates. The results revealed the dynamic metabolic strategies this methylotroph has for processing both simple one-carbon compounds and the complex multicarbon substrates of naturally derived marine organic matter and provide baseline quantitative data for identifying their in situ activities and impact on the marine carbon cycle.

scholarly journals Solid organics in cometary comae

2008 ◽  
Vol 4 (S251) ◽  
pp. 313-314
Author(s):  
Gian Paolo Tozzi ◽  
Ludmilla Kolokolova
Keyword(s):  
Organic Matter ◽  
Data Analysis ◽  
Light Scattering ◽  
Space Missions ◽  
Good Evidence ◽  
Specific Data ◽  
Distributed Source ◽  
Cometary Comae

AbstractIt is known since long ago that in comets a large quantity of organic matter exists in form of grains or is embedded in silicate grains. This was detected in situ by cometary space missions as well as inferred as a distributed source of some molecules observed in comets. Since organic matter is rather volatile, finding slow sublimating grains in comets can be good evidence of organics as a constituent of such grains. Here we describe a method to detect sublimating grains in comets. It consists of specific observations, specific data analysis, and some light-scattering modeling. We detect sublimating grains by measuring the quantity of grains as a function of the nucleocentric distance. Once detected, it is possible to get their photometric characteristics and compare them with the results of light-scattering modeling. The method has been applied to several comets. Sublimating grains were reliably identified for two of them.

scholarly journals Distribution and Bioconcentration of Polycyclic Aromatic Hydrocarbons in Surface Water and Fishes

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Haiyan Li ◽  
Yong Ran
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Solid Phase ◽  
Critical Factor ◽  
Ring Compounds ◽  
Maximum Value ◽  
Fish Samples ◽  
Polycyclic Aromatic ◽  
Partitioning Coefficients

To examine spatial distribution and bioconcentration of PAHs, water and fish samples were collected from Pearl River Delta in summer and spring, respectively. Particulate organic carbon, dissolved organic carbon, biodegradable DOC (BDOC), and chlorophyll a were measured. PAHs were dominated by 2- and 3-ring compounds in the water and SPM samples. Aqueous and solid-phase PAHs, respectively, showed significant correlations with total organic matter (TOC) in SPM or dissolved organic matter (DOC) in the water. The in-situ partitioning coefficients (logKoc, mL/g) for the samples were observed to be related tologKow, implying that the hydrophobicity of PAHs is a critical factor in their distribution. It was also observed that BCF increased with the increasingKowin the viscera of tilapia (logBCF=0.507logKow−1.368,r=0.883). However, most of the observed log BCF values in other different fish tissues at first increased with the increasing of logKow, then reached a maximum value whenlogKowis between 5 and 7, and then decreased whenlogKowis higher than 7, indicating that the value of BCF may vary due to the diversity of fish species.

Photosensitized degradation kinetics of trace halogenated contaminants in natural waters using membrane introduction mass spectrometry as an in situ reaction monitor

2015 ◽  
Vol 14 (11) ◽  
pp. 2108-2118 ◽  
Author(s):  
Dane R. Letourneau ◽  
Chris G. Gill ◽  
Erik T. Krogh
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Natural Waters ◽  
Degradation Kinetics ◽  
Reductive Dehalogenation ◽  
Membrane Introduction Mass Spectrometry ◽  
Naturally Occurring ◽  
On Line ◽  
Kinetics Of

On-line membrane introduction mass spectrometry used to directly measure the photosensitized reductive dehalogenation kinetics of trace aqueous halocarbons in the presence of naturally occurring dissolved organic matter.

scholarly journals Complex organic matter in Titan's atmospheric aerosols from in situ pyrolysis and analysis

Nature ◽  
2005 ◽  
Vol 438 (7069) ◽  
pp. 796-799 ◽  
Author(s):  
G. Israël ◽  
C. Szopa ◽  
F. Raulin ◽  
M. Cabane ◽  
H. B. Niemann ◽  
...  
Keyword(s):  
Organic Matter ◽  
Atmospheric Aerosols ◽  
Complex Organic

Photochemical Evolution of Interstellar/Precometary Organic Material

1997 ◽  
Vol 161 ◽  
pp. 23-47 ◽  
Author(s):  
Louis J. Allamandola ◽  
Max P. Bernstein ◽  
Scott A. Sandford
Keyword(s):  
Origin Of Life ◽  
Building Blocks ◽  
Complex Species ◽  
Infrared Observations ◽  
Interstellar Ice ◽  
Polycyclic Aromatic ◽  
Ultraviolet Photolysis ◽  
The Origin Of Life ◽  
Simple Molecules ◽  
Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

1999 ◽  
Vol 173 ◽  
pp. 365-370
Author(s):  
Kh.I. Ibadinov
Keyword(s):  
Laboratory Experiments ◽  
Cometary Nucleus ◽  
Sublimation Rate ◽  
Cometary Nuclei ◽  
Short Period Comet ◽  
Short Period ◽  
Brightness Decrease ◽  
Crust Thickness ◽  
Ice Sublimation ◽  
Period Comet

AbstractFrom the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

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