21 research outputs found
Multi-instrument analysis of 67P/Churyumov-Gerasimenko coma particles: COPS-GIADA data fusion
No full textContext. The European Space Agency ' s Rosetta mission to comet 67P/Churyumov-Gerasimenko has offered scientists the opportunity to study a comet in unprecedented detail. Four instruments of the Rosetta orbiter, namely, the Micro-Imaging Dust Analysis System (MIDAS), the Grain Impact Analyzer and Dust Accumulator (GIADA), the COmetary Secondary Ion Mass Analyser (COSIMA), and the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) have provided information on cometary dust particles. Cross-instrument comparisons are crucial to characterize cometary dust particles beyond the capabilities of individual sensors, as they are sensitive to different dust components.Aims. We present the first comparison between detections of the ROSINA COmet Pressure Sensor (COPS) and GIADA. These two instruments are complementary as the former is sensitive solely to volatiles of icy particles, while the latter measured the dust particle as a whole, including refractories and condensed (semi)volatiles. Our goal is to correlate the particles detected by COPS and GIADA and to assess whether they belong to a common group.Methods. We statistically analyzed the in situ data of COPS and GIADA by calculating Pearson correlation coefficients.Results. Among the several types of particles detected by GIADA, we find that COPS particles are significantly correlated solely with GIADA fluffy agglomerates (Pearson correlation coefficient of 0.55 and p-value of 4.6 x 10(-3)). This suggests that fluffy particles are composed of both refractories and volatiles. COPS volatile volumes, which may be represented by equivalent spheres with a diameter in the range between 0.06 mu m and 0.8 mu m, are similar to the sizes of the fractal particle ' s subunits identified by MIDAS (i.e., 0.05-0.18 mu m)
Mecanismos de formación y estabilización de la materia orgánica en el suelo: una mirada desde la ecología funcional
No full textLa descomposición del materia vegetal muerto (MVM) es fundamental para servicios ecosistémicos como la fertilidad del suelo, a través de los nutrientes que deja disponibles este proceso, y la regulación climática, a través del C que se resulta almacenado en el suelo. Tradicionalmente, los estudios de descomposición de MVM, consideraron que la pérdida de masa de ese material representa tanto el CO2 que se libera a la atmósfera producto de la descomposición como de a los nutrientes que quedan disponibles en el suelo. Por su parte, el MVM remanente representaba la contribución de la descomposición a la formación y estabilización de materia orgánica del suelo (MOS). Este marco conceptual no consideraba a los productos de re-síntesis microbiana y a los complejos órgano-minerales en la matriz del suelo cuya formación, según se ha demostrado en los últimos años, es de fundamental importancia en la estabilización de la MOS. Si los productos de re-síntesis microbiana fueran la fuente principal de MOS estabilizada, tanto la disponibilidad de nutrientes como la estabilización de la MOS serían favorecidas por el ingreso de sustratos más fáciles de descomponer, que promuevan la actividad microbiana. Es decir, por sustratos provenientes de plantas de crecimiento rápido, con baja relación C:N y tejidos blandos. Mientras que, si la estabilización de la MOS estuviera determinada fundamentalmente por los procesos abióticos que determinan la formación de complejos órgano minerales en el suelo, lo relevante en este proceso sería la cantidad del MVM que interactua con la matriz mineral y no tanto la calidad de la misma. Evaluar la importancia relativa de estos procesos es imprescindible para entender como los cambios en la vegetación producto de cambios climáticos o en el uso de la tierra afectarán de forma sinérgica o antagónica a los servicios ecosistémicos asociados al reciclado del MVM.Fil: Pérez Harguindeguy, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Vaieretti, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Kowaljow, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Conti, Georgina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pestoni, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Naldini, B.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Poca, María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaIV Jornadas Nacionales de Suelos de Ambientes SemiáridosCórdobaArgentinaUniversidad Nacional de Córdoba. Facultad de Ciencias Agropecuaria
Multi-instrument analysis of 67P/Churyumov-Gerasimenko coma particles: COPS-GIADA data fusion
No full textThe European Space Agency's Rosetta mission to comet
67P/Churyumov-Gerasimenko has offered scientists the opportunity to study a
comet in unprecedented detail. Four instruments of the Rosetta orbiter, namely,
the Micro-Imaging Dust Analysis System (MIDAS), the Grain Impact Analyzer and
Dust Accumulator (GIADA), the COmetary Secondary Ion Mass Analyser (COSIMA),
and the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) have
provided information on cometary dust particles. Cross-instrument comparisons
are crucial to characterize cometary dust particles beyond the capabilities of
individual sensors, as they are sensitive to different dust components. We
present the first comparison between detections of the ROSINA COmet Pressure
Sensor (COPS) and GIADA. These two instruments are complementary as the former
is sensitive solely to volatiles of icy particles, while the latter measured
the dust particle as a whole, including refractories and condensed
(semi)volatiles. Our goal is to correlate the particles detected by COPS and
GIADA and to assess whether they belong to a common group. We statistically
analyzed the in situ data of COPS and GIADA by calculating Pearson correlation
coefficients. Among the several types of particles detected by GIADA, we find
that COPS particles are significantly correlated solely with GIADA fluffy
agglomerates (Pearson correlation coefficient of 0.55 and p-value of ). This suggests that fluffy particles are composed of both
refractories and volatiles. COPS volatile volumes, which may be represented by
equivalent spheres with a diameter in the range between 0.06 m and 0.8
m, are similar to the sizes of the fractal particle's subunits identified
by MIDAS (i.e., 0.05-0.18 m).Comment: 6 pages, 3 figures, accepted for publication in A&
No detectable upper limit when predicting soil mineral-associated organic carbon stabilization capacity in temperate grassland of Central Argentina mountains
No full textSoil organic carbon (SOC) is the major active organic carbon (OC) reservoir within terrestrial ecosystems. SOC is stored in different soil organic matter fractions, among which mineral-associated organic matter is considered the more stable. It has been proposed that the OC stored in this fraction (i.e., MAOC-mineral associated organic carbon) depends on the proportion of fine soil particles. This idea has been challenged by studies that found soils with significantly higher MAOC values than predicted by several models. We assessed the soil MAOC contents in central Argentina mountain grasslands. These soils store high OC contents, and thus may constitute a valuable case to evaluate the soils' saturation behavior. We compared the actual soil MAOC content of these mountain grasslands with the predictions from different MAOC saturation models, and we explored if there were indications of saturation behavior by: a) plotting the MAOC against the total SOC contents, and b) by plotting the OC contents in the fine fraction against the fine soil particles content. We found a positive relationship between MAOC and the fine particle content in the soils studied. However, we also found that even the model with the highest upper limit of MAOC stabilization underestimated the MAOC contents of these grasslands. In addition, we found the absence of an inflection point when plotting the MAOC against total SOC contents. Finally, we observed a weak but significant negative relationship between the concentration of OC in the fine fraction and the proportion of the fine fraction of the soil, with high OC loading values in the coarser soils. These last patterns could be indicators of non-saturation behavior. Our results provide additional evidence that many of the models currently used for predicting the OC saturation deficit of soils may be underestimating the potential MAOC stabilization capacity of certain soils. Additionally, our findings contribute to the evidence challenging the ideas of OC saturation on a fine soil particles basis. We highlight some lines of research that should be developed to confirm the existence of a MAOC saturation behavior, as well as to continue exploring the drivers of OC accrual in different systems.Fil: Fernández Catinot, Franco Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pestoni, Sofía. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Gallardo, Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Vaieretti, Maria Victoria. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pérez Harguindeguy, Natalia. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin
Detection of volatiles undergoing sublimation from 67P/Churyumov-Gerasimenko coma particles using ROSINA/COPS
No full textContext. The ESA Rosetta mission has allowed for an extensive in situ study of the comet 67P/Churyumov-Gerasimenko. In measurements performed by the ram gauge of the COmet Pressure Sensor (COPS), observed features are seen to deviate from the nominal ram gauge signal. This effect is attributable to the sublimation of the volatile fraction of cometary icy particles containing volatiles and refractories.
Aims. The objective of this work is to investigate the volatile content of icy particles that enter the COPS ram gauge.
Methods. We inspected the ram gauge measurements to search for features associated with the sublimation of the volatile component of cometary particles impacting the instrument. All the sublimation features with a high-enough signal-to-noise ratio were modelled by fitting one or more exponential decay functions. The parameters of these fits were used to categorise different compositions of the sublimating component.
Results. Based on features that are attributable to ice sublimation, we infer the detection of 73 icy particles containing volatiles. Of these, 25 detections have enough volatile content for an in-depth study. From the values of the exponential decay constants, we classified the 25 inferred icy particles into three types, interpreted as different volatile compositions, which are possibly further complicated by their differing morphologies. The available data do not give any indication as to which molecules compose the different types. Nevertheless, we can estimate the total volume of volatiles, which is expressed as the diameter of an equivalent sphere of water (density of 1 g cm−3). This result was found to be on the order of hundreds of nanometres
Socioeconomic characteristics and healthy lifestyle behaviors of cancer survivors by lifestyle score category and combined (n = 522)<sup>a</sup><sup>,</sup><sup>b</sup>.
No full textSocioeconomic characteristics and healthy lifestyle behaviors of cancer survivors by lifestyle score category and combined (n = 522)a,b.</p
67P/Churyumov–Gerasimenko’s dust activity from pre- to post-perihelion as detected by Rosetta/GIADA
No full textWe characterized the 67P/Churyumov–Gerasimenko’s dust activity, by analysing individual dust particle velocity and momentum measurements of Grain Impact Analyser and Dust Accumulator (GIADA), the dust detector onboard the ESA/Rosetta spacecraft, collecting dust from tens to hundreds of kilometres from the nucleus. Specifically, we developed a procedure to trace back the motion of dust particles down to the nucleus, identifying the surface’s region ejecting each dust particle. This procedure has been developed and validated for the first part of the mission by Longobardo et al. and was extended to the entire GIADA data set in this work. The results based on this technique allowed us to investigate the link between the dust porosity (fluffy/compact) and the morphology of the ejecting surface (rough/smooth). We found that fluffy and compact particles, despite the lack of correlation in their coma spatial distribution (at large nucleocentric distances) induced by their different velocities, have common ejection regions. In particular, the correlation between the distributions of fluffy and compact particles is maintained up to an altitude of about 10 km. Fluffy particles are more abundant in rough terrains. This could be the result of past cometary activity that resurfaced the smooth terrains and/or of the comet formation process that stored the fluffy particles inside the voids between the pebbles. The variation of fluffy particle concentration between rough and smooth terrains agrees with predictions of comet formation models. Finally, no correlation between dust distribution on the nucleus and surface thermal properties was found
Abundant ammonium hydrosulphide embedded in cometary dust grains
No full textAmmonium hydrosulphide has long since been postulated to exist at least in certain layers of the giant planets. Its radiation products may be the reason for the red colour seen on Jupiter. Several ammonium salts, the products of NH3, and an acid have previously been detected at comet 67P/Churyumov-Gerasimenko. The acid H2S is the fifth most abundant molecule in the coma of 67P followed by NH3. In order to look for the salt NH4+SH−, we analysed in situ measurements from the Rosetta/ROSINA Double Focusing Mass Spectrometer during the Rosetta mission. NH3 and H2S appear to be independent of each other when sublimating directly from the nucleus. However, we observe a strong correlation between the two species during dust impacts, clearly pointing to the salt. We find that NH4+SH− is by far the most abundant salt, more abundant in the dust impacts than even water. We also find all previously detected ammonium salts and for the first time ammonium fluoride. The amount of ammonia and acids balance each other, confirming that ammonia is mostly in the form of salt embedded into dust grains. Allotropes S2 and S3 are strongly enhanced in the impacts, while H2S2 and its fragment HS2 are not detected, which is most probably the result of radiolysis of NH4+SH−. This makes a prestellar origin of the salt likely. Our findings may explain the apparent depletion of nitrogen in comets and maybe help to solve the riddle of the missing sulphur in star-forming regions
Cyanogen, cyanoacetylene, and acetonitrile in comet 67P and their relation to the cyano radical
No full textThe cyano radical (CN) is one of the most frequently remotely observed species in space, and is also often observed in comets. Data for the inner coma of comet 67P/Churyumov-Gerasimenko collected by the high-resolution Double Focusing Mass Spectrometer (DFMS) on board the Rosetta orbiter revealed an unexpected chemical complexity, and, recently, also more CN than expected from photodissociation of its most likely parent, hydrogen cyanide (HCN). Here, we derive abundances relative to HCN of three cometary nitriles (including structural isomers) from DFMS data. Mass spectrometry of complex mixtures does not always allow isolation of structural isomers, and therefore in our analysis we assume the most stable and abundant (in similar environments) structure, that is HCN for CHN, CH3CN for C2H3N, HC3N for C3HN, and NCCN for C2N2. For cyanoacetylene (HC3N) and acetonitrile (CH3CN), the complete mission time-line was evaluated, while cyanogen (NCCN) was often below the detection limit. By carefully selecting periods where cyanogen was above the detection limit, we were able to follow the abundance ratio between NCCN and HCN from 3.16 au inbound to 3.42 au outbound. These are the first measurements of NCCN in a comet. We find that neither NCCN nor either of the other two nitriles is sufficiently abundant to be a relevant alternative parent to CN
