Class Of Comets Research Articles

Evaluation of water genotoxicity using comet assay in two freshwater fish species, Wallago attu and Ompok bimaculatus in Kabul River, Pakistan

The investigation determines the pollution status of river Kabul and its effects on the DNA of Wallago attu and Ompok bimaculatus. River Kabul gets pollutants from Amanghar industries and sewages from Mardan, Nowshera and Peshawar. Water and fish samples are taken to study heavy metals and physical parameters. The overall sequence of physical parameters in water samples was TDS>TSS>EC>TA>Cl>Na>pH>K, and that of heavy metals was Zn>Cr>Mn> Fe>Cu>Pb>Ni>Cd. The studied parameters in all the water samples except TSS are within the proposed limits of national environmental quality standards. The overall trend of analysed water samples was C>B>A. The study determines the effects of water pollution on the DNA of Ompok bimaculatus and Wallago attu tissues. Therefore, degrees of DNA damage such as TCS and comet class are studied in gills, liver, muscles, and intestines of Wallago attu and Ompok bimaculatus. The trend of DNA damage in examined tissues was intestine>skin>liver>gills>muscle, and in studied fish species, it was Ompok bimaculatus>Wallago attu. More significant DNA damage was observed in the intestine and smaller in the muscle. More DNA damage was found in Ompok bimaculatus and less in Wallago attu. The investigation recommended detoxifying the effluents and sewages before discharging them in River Kabul.

AMBITION – comet nucleus cryogenic sample return

We describe the AMBITION project, a mission to return the first-ever cryogenically-stored sample of a cometary nucleus, that has been proposed for the ESA Science Programme Voyage 2050. Comets are the leftover building blocks of giant planet cores and other planetary bodies, and fingerprints of Solar System’s formation processes. We summarise some of the most important questions still open in cometary science and Solar System formation after the successful Rosetta mission. We show that many of these scientific questions require sample analysis using techniques that are only possible in laboratories on Earth. We summarize measurements, instrumentation and mission scenarios that can address these questions. We emphasize the need for returning a sample collected at depth or, still more challenging, at cryogenic temperatures while preserving the stratigraphy of the comet nucleus surface layers. We provide requirements for the next generation of landers, for cryogenic sample acquisition and storage during the return to Earth. Rendezvous missions to the main belt comets and Centaurs, expanding our knowledge by exploring new classes of comets, are also discussed. The AMBITION project is discussed in the international context of comet and asteroid space exploration.

The “memory” of the Oort cloud

Aims. Our aim in this paper is to try to discover if we can find any record of the Oort cloud formation process in the orbital distribution of currently observable long-periodic comets. Methods. Long-term simulations of tens of millions of comets from two different kinds of proto-Oort clouds (isotropic and disk-like) were performed. In these simulations we considered the Galactic tides, stellar passage, and planetary perturbations. Results. In the case of an initially disk-like proto-Oort cloud, the final Oort cloud remains anisotroic inside of about 13 200 au. A record of the initial shape is preserved, here referred to as the “memory”, even on the final distribution of observable comets. This memory is measurable in particular for observable comets for which the previous perihelion was beyond 10 au and that were significantly affected by Uranus or Neptune at that moment (the so-called Kaib-Quinn jumpers observable class). Indeed, these comets are strongly concentrated along an extended scattered disk that is the remnant of the initial population 1 Gyr before the comets are observable. In addition, for this class of comets, the distributions of ecliptic inclination and Galactic longitude of the ascending node at the previous perihelion preceding the observable perihelion highlight characteristics that are not present in the isotropic model. Furthermore, the disk-like model produces four times more observable comets than the isotropic one, and its flux is independent of the initial distribution of orbital energy. Also for the disk-like model, the region beyond Neptune up to ~40 au gives the major contribution to the final flux of observable comets. Conclusions. The disk-like model sustains a flux of observable comets that are more consistent with the actually observed flux than using the isotropic model. However, further investigations are needed to reveal whether a fingerprint of the initial proto-Oort cloud, such as those highlighted in the present article, is present in the sample of known long-period comets.

Differential pulmonary in vitro toxicity of two small-sized polyvinylpyrrolidone-coated silver nanoparticles

ABSTRACTSilver nanoparticles (AgNP), with their important properties, are being used in a range of sectors from industry to medicine, leading to increased human exposure. Hence, their toxicity potential needs to be comprehensively evaluated. It was postulated that within small-sized (≤20 nm) polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNP), minor size differences may significantly induce different toxicity profiles and involve varying cellular pathways. Therefore, the aim of this study was to examine the influence of differing size AgNP with 10 nm (AgNP10) and 20 nm (AgNP20) (up to 100 µg/ml), as well as to ionic silver as AgNO3 for 24 and 48 h, using the human lung cell line A549. The effects on cell viability, proliferation, apoptosis, DNA damage and cell cycle dynamics were assessed. Results for both time periods showed that for low concentrations (<5 µg/ml), AgNP20 were more cytotoxic than AgNP10, however, at higher doses, AgNP10 exhibited higher toxicity. For concentrations >50 µg/ml, AgNP10 induced severe DNA damage (comet class 3–4), cell cycle arrest at G2 phase and late-stage apoptosis, while AgNP20 induced cell cycle arrest at S phase and an increase in the percentage sub-G1, which did not recover after 48 h, and late-stage apoptosis/necrosis. In longer-term exposures, the greater impairment in colony formation due to AgNP exposure than to silver ion supports that nanotoxicity is not exclusively due to the released ion. Data suggest that toxicity mediated by small AgNP (≤20 nm) in lung cells is not only dependent on the level of particle internalization, but also on AgNP size and concentration, which may involve varying pathways as targets.

Biomarkers of waterborne copper exposure in the Neotropical fish Prochilodus lineatus

The main goal of the present study was to investigate the effects of acute exposure to copper (Cu) using a Neotropical freshwater fish as sentinel species through multi biomarkers analysis at different biological levels. Juveniles of Prochilodus lineatus were kept under control condition (no Cu addition in the water) or exposed to environmentally relevant concentrations of waterborne Cu (5, 9 and 20μgL−1) for 96h. These concentrations were selected to bracket the current Brazilian water quality criteria for Cu in fresh water (9 and 13μgL−1 dissolved copper). Endpoints analyzed included ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity, reduced glutathione (GSH) and metallothionein-like protein (MT) concentration, lipid peroxidation (LPO) level, tissue damage index, and incidence of free melano-macrophages (FMM) and melano-macrophage centers (MMC) in the liver. They also included DNA damage (frequency of nucleoids per comet class, number of damaged nucleoids per fish and DNA damage score) in erythrocytes, as well as muscle and brain acetylcholinesterase (AChE) activity and behavioral parameters (swimming distance and velocity, time spent swimming and swimming activity in the upper and lower layers of the water column). Fish exposed to any of the Cu concentrations tested showed increased liver MT concentration and LPO level, higher number of damaged nucleoids in erythrocytes per fish, and inhibited muscle AChE activity. Also, increased liver SOD activity was observed in fish exposed to 9 and 20μgL−1 Cu. Fish exposed to 5 and 9μgL−1 Cu spent lower amount of time swimming. Fish exposed to 9μgL−1 Cu showed increased swimming distance and velocity while those exposed to 20μgL−1 Cu had lower swimming distance and velocity, as well as, spent less time swimming in the lower layer of the water column when compared to those kept under control condition. These findings indicate that Cu exposure at environmentally relevant concentrations (below or close to the current Brazilian water quality criteria) induced significant biological (histological, biochemical and genetic) and ecological (swimming and exploratory abilities) damages in the Neotropical fish P. lineatus. They also suggest that MT concentration, DNA damage (comet assay), LPO (TBARS method), SOD and AChE activity, together with swimming behavior analyses are potential biomarkers to assess and monitor areas impacted by Cu in fresh water.

Active Asteroids: Main-Belt Comets and Disrupted Asteroids

AbstractThe study of active asteroids has attracted a great deal of interest in recent years since the recognition of main-belt comets (which orbit in the main asteroid belt, but exhibit comet-like activity due to the sublimation of volatile ices) as a new class of comets in 2006, and the discovery of the first disrupted asteroids (which, unlike MBCs, exhibit comet-like activity due to a physical disruption such as an impact or rotational destabilization, not sublimation) in 2010. In this paper, I will briefly discuss key areas of interest in the study of active asteroids.

Dust coma of comet C/2009 P1 (Garradd) by imaging polarimetry

AbstractComet C/2009 P1 (Garradd) was observed by imaging polarimetry for nearly 5 months from October 2011 to March 2012, over an intermediate phase angle range (28°–35°). Two months before perihelion and one month after, dust particles seem to be ejected all around the optocenter and jets extend to distances greater than 40,000 km. An increase of activity is noticed in intensity and polarization after perihelion. Two months before perihelion and one month after, the dust emission seems to be all around the optocenter. Two and three months after perihelion the jets are mainly toward the solar direction with an extension of more than 20,000 km projected on the sky. The values of the aperture polarization are comparable to those of other comets. On the polarization maps in October 2011 and January 2012 the higher polarization zones extend in large regions perpendicularly to the solar direction where jets are also observed. In February and March 2012, the polarization in the jets is larger in the solar direction than in the surrounding coma. By its activity visible on intensity images and polarization maps at large distances from the nucleus, comet Garradd probably belongs to the high‐Pmax class of comets.

Comet assay in myelodysplastic syndromes

The comet assay (single-cell gel electrophoresis) has been established as a simple, rapid, flexible and sensitive method of detecting DNA damage in single cells(1,2). Cells embedded in agarose on a microscope slide are lysed with detergent. Electrophoresis at high pH results in structures resembling comets, observed by fluorescence microscopy; the intensity of the comet tail relative to the head reflects DNA damage(2). The lesion of each cell is quantified according to the comet tail length as class 0 (no tail) to 4 (almost all DNA in tail)(3). Due to genetic instability of myelodysplastic syndromes, the comet assay can be useful to detect DNA lesion intensity and correlate this with cytogenetic abnormalities. Figure 1 illustrates a cell from a healthy 46-year-old control individual classified as comet class 0. Figures 2A - E illustrate cells from a 61-year-old patient with myelodysplastic syndrome (47, XY, +8) classified as comet class 0, 1 and 2. Figure 1 - Figures 2A – E Electrophoresis under alkaline conditions in low melting point agarose gel of the cells of a healthy control classified as comet Class 0.

Comet Assay as a technique to evaluate DNA damage in sickle cell anemia patients

Comet Assay is a technique which can detect single-strand breaks as initial DNA damage.(1,2) Cells submitted to electrophoresis under alkaline conditions in low melting point agarose gel show DNA damage in a comet-like form when viewed at fluorescence microscopy. The lesion from each cell is quantified according to the comet tail length as class 0, 1, 2 or 3.(3) In sickle cell disease, due to constant oxidative stress and membrane lesions, this assay can be useful to detect DNA lesion intensity and medication response. Figure 1A illustrates cell nuclei from a 31-year-old sickle cell disease patient taking hydroxyurea classified as comet class 3. Figure 1B shows the result of a 33-year-old subject without any hemoglobinopathy where no lesions are observed. Figure 1A/Figure 1B Electrophoresis under alkaline conditions in low melting point agarose gel of the cells of a sickle cell disease patient with damage classified as Comet class 3

Thirty years of cometary spectroscopy from McDonald Observatory

We report on the results of a spectroscopic survey of 130 comets that was conducted at McDonald Observatory from 1980 through 2008. Some of the comets were observed on only one night, while others were observed repeatedly. For 20 of these comets, no molecules were detected. For the remaining 110 comets, some emission from CN, OH, NH, C3, C2, CH, and NH2 molecules were observed on at least one occasion. We converted the observed molecular column densities to production rates using a Haser (Haser, L. [1957]. Liege Inst. Astrophysics Reprint No. 394) model. We defined a restricted data set of comets that had at least three nights of observations. The restricted data set consists of 59 comets. We used ratios of production rates to study the trends in the data. We find two classes of comets: typical and carbon-chain depleted comets. Using a very strict definition of depleted comets, requiring C2and C3 to both be depleted, we find 9% of our restricted data set comets to be depleted. Using a more relaxed definition that requires only C2 to be below a threshold (similar to other researchers), we find 25% of the comets are depleted. Two-thirds of the depleted comets are Jupiter Family comets, while one-third are Long Period comets. 37% of the Jupiter Family comets are depleted, while 18.5% of the Long Period comets are depleted. We compare our results with other studies and find good agreement.

Use of native species Crenicichla menezesi (Ariidae) as a model for in situ evaluation of genotoxicity in surface water

The aim of this work was to analyze the genotoxicity in surface water from the Pitimbú River (Natal, Brazil) using a neotropical species Crenicichla menezesi as bioindicator for in situ evaluation. The genotoxicity was analyzed using the micronucleus (MN) and comet assays in erythrocytes. The animals were collected from five sites of the river. A significant increase of MN frequency and comet class L1 to L4 were observed only in specimens collected from three sampling sites (SS3, SS4 and SS5) located into urban areas. These same sites also presented high metals concentration. Correlation of DNA damage and concentrations of Cu (Spearman r = 0.8080), Cr (Spearman r = 0.9772), and Ni (Spearman r = 0.9909) were observed. These data indicate the presence of genotoxic agents. Moreover the C. menezesi species showed to be a good indicator for prompt analyses since this species presents sedentary and carnivore habits.

Atlas of secular light curves of comets

In this work we have compiled 37,692 observations of 27 periodic and non-periodic comets to create the secular light curves (SLCs), using two plots per comet. The data have been reduced homogeneously. Our overriding goal is to learn the properties of the ensemble of comets. More than 30 parameters are listed, of which over ∼20 are new and measured from the plots. We define two ages for a comet using activity as a proxy, the photometric age P-AGE, and the time-age, T-AGE. It is shown that these parameters are robust, implying that the input data can have significant errors but P-AGE and T-AGE come out with small errors. This is due to their mathematical definition. It is shown that P-AGE classifies comets by shape of their light curve. The value of this Atlas is twofold: The SLCs not only show what we know, but also show what we do not know, thus pointing the way to meaningful observations. Besides their scientific value, these plots are useful for planning observations. The SLCs have not been modeled, and there is no cometary light curve standard model as there is for some variable stars (i.e. eclipsing binaries). Comets are classified by age and size. In this way it is found that 29P/Schwassmann-Wachmann 1 is a baby goliath comet, while C/1983 J1 Sugano-Saigusa-Fujikawa is a middle age dwarf. There are new classes of comets based on their photometric properties. The secular light curves presented in this Atlas exhibit complexity beyond current understanding.

The Chemical Diversity of Comets: Synergies Between Space Exploration and Ground-based Radio Observations

A fundamental question in cometary science is whether the different dynamical classes of comets have different chemical compositions, which would reflect different initial conditions. From the ground or Earth orbit, radio and infrared spectroscopic observations of a now significant sample of comets indeed reveal deep differences in the relative abundances of cometary ices. However, no obvious correlation with dynamical classes is found. Further results come, or are expected, from space exploration. Such investigations, by nature limited to a small number of objects, are unfortunately focussed on short-period comets (mainly Jupiter-family). But these in situ studies provide “ground truth” for remote sensing. We discuss the chemical differences in comets from our database of spectroscopic radio observations, which has been recently enriched by several Jupiter-family and Halley-type comets.

THE EXTREMELY ANOMALOUS MOLECULAR ABUNDANCES OF COMET 96P/MACHHOLZ 1 FROM NARROWBAND PHOTOMETRY

Narrowband-filter photometry of Comet 96P/Machholz 1 was obtained at Lowell Observatory during the comet's 2007 apparition. Production rates of OH, CN, C2, C3, and NH were derived from these data sets, and the quantity A(θ)fρ—a proxy measure of the dust production—was also calculated. Relative abundances, expressed as ratios of production rates with respect to OH (a measure of the water abundance), were compared to those measured in other comets. Comet Machholz 1 is shown to be depleted of CN by about a factor of 72 from average, while C2 and C3 are also low, but only by factors of 8 and 19, respectively, from typical composition (based on an update to the classifications by A'Hearn et al.). In contrast, NH is near the mid-to-upper end of its normal range. This extremely low CN-to-OH ratio for Machholz 1 indicates that it is either compositionally associated with Comet Yanaka (1988r; 1988 Y1), which was strongly depleted in CN and C2, but not NH2, or represents a new compositional class of comets, since Yanaka had a much greater depletion of C2 (>100×) than did Machholz 1 (8×). Evidence strongly suggests that the extremely anomalous compositions of these two comets are primordial rather than from recent thermal processing. It remains unclear whether these comets formed at a location in our solar system with unusual conditions and a low probability of being gravitationally perturbed into the inner solar system, or if one or both objects are interstellar interlopers.

Imaging polarimetry of the dust coma of Comet Tempel 1 before and after Deep Impact at Haute-Provence Observatory

We have observed the coma of Comet 9P/Tempel 1, the target of the Deep Impact mission, by the polarization imaging technique, before and after the impact event (−32, −7, +43 and +65 h). Our observations were conducted in the red wavelength domain from Haute-Provence Observatory (France), with the 80-cm telescope. The overall polarization of 9P/Tempel 1, as obtained near 41° phase angle, is monitored and compared to data from other (active and less active) comets studied by the same technique. The linear polarization of the dust ejected by the impact is compared to previous observations of dust present in jets, ejected during outbursts or released when comets happen to split. At phase angles of about 41°, the difference in polarization between the comets with a low maximum in polarization and the comets with a high maximum in polarization is about 1%; it may thus be difficult to conclude about the classification. Nevertheless, the overall polarization after the impact rapidly reached a value corresponding to the high polarization class of comets, and later progressively decreased to its initial value. The polarization was measured to be slightly lower (about 1%) before the impact than after it in a 26,000-km aperture. The plume formed from dust ejected by the impact was still present 65 h after it. The variations of the intensity and the polarization in the coma provide some clues to variations of the physical properties of the particles; comparison with other techniques corroborates the presence of large particles and of submicron-sized grains in aggregates.

Imaging polarimetry of the dust coma of Comet Tempel 1 before and after Deep Impact at Haute-Provence Observatory

We have observed the coma of Comet 9P/Tempel 1, the target of the Deep Impact mission, by the polarization imaging technique, before and after the impact event (−32, −7, +43 and +65 h). Our observations were conducted in the red wavelength domain from Haute-Provence Observatory (France), with the 80-cm telescope. The overall polarization of 9P/Tempel 1, as obtained near 41° phase angle, is monitored and compared to data from other (active and less active) comets studied by the same technique. The linear polarization of the dust ejected by the impact is compared to previous observations of dust present in jets, ejected during outbursts or released when comets happen to split. At phase angles of about 41°, the difference in polarization between the comets with a low maximum in polarization and the comets with a high maximum in polarization is about 1%; it may thus be difficult to conclude about the classification. Nevertheless, the overall polarization after the impact rapidly reached a value corresponding to the high polarization class of comets, and later progressively decreased to its initial value. The polarization was measured to be slightly lower (about 1%) before the impact than after it in a 26,000-km aperture. The plume formed from dust ejected by the impact was still present 65 h after it. The variations of the intensity and the polarization in the coma provide some clues to variations of the physical properties of the particles; comparison with other techniques corroborates the presence of large particles and of submicron-sized grains in aggregates.

Correlation of the cytotoxic activity of four different alkaloids, from Chelidonium majus (greater celandine), with their DNA intercalating properties and ability to induce breaks in the DNA of NK/Ly murine lymphoma cells

AbstractThe purpose of this study was to examine the relationship between the DNA intercalating characteristics and the DNA damaging capacity of four alkaloids extracted from Chelidonium majus L, as well as their toxicity towards murine NK/Ly lymphoma cells. Chelerythrine, sanguinarine and coptisine were found to be intercalated into the DNA isolated from NK/Ly cells, meanwhile, chelidonine exhibited no affinity to DNA. Sanguinarine exhibited the greatest toxicity toward NK/Ly cells, and the toxicity of the other three decreased in descending order: chelerythrine, coptisine and chelidonine. Chelerythrine and sanguinarine caused DNA damage, illustrated by the formation of comets of the third class. Coptisine was less toxic than chelerythrine and sanguinarine, and affected the formation the same class of comets in higher concentration. The quantity of comets induced by chelidonine were negligible, a finding consistent with its inability to intercalate into DNA structure. The ability of four main alkaloids of Chelidonium majus L., to intercalate into DNA isolated from murine NK/Ly lymphoma cells, correlated with their ability to induce breaks in cellular DNA and with their toxic effect towards those cells.

CCD imaging and aperture polarimetry of comet 2P/Encke: are there two polarimetric classes of comets?

We present results of imaging and aperture polarimetry of the dust of comet 2P/Encke at phase angles 91–105°, obtained during the 2003 apparition. We investigate how strongly molecular emissions transmitted by the filters used in the observations can affect the resulting polarization of cometary dust. This problem is of particular importance for so-called gas-rich comets like comet 2P/Encke which has particularly strong molecular emission as compared to its dust continuum. Aperture polarimetry in the wide-band UBVR filters was performed at the 2.6-m Shain telescope and 1.25-m telescope of the Crimean Astrophysical Observatory on November 17–24. From these measurements a dust polarization of ≈ % is derived, which puts the comet in the class of comets with low polarization. The imaging observations of comet 2P/Encke were carried out at the 2-m telescope of the Bulgarian National Astronomical Observatory on November 20–22, 2003. Narrow-band filters centered on the 0–7–0 transition of the A 2A_1 – 2B_1 electronic band system of NH2 (662 nm) and on an adjacent red continuum at 642 nm were employed. The polarization of NH2 averaged over the 0–7–0 vibronic transition amounts to ≈ % at phase angles close 90°, similar to the polarization of the two-atomic molecules CN and C2 . The dust polarization however, when corrected for the effect of molecular emissions, is larger than 30%. We conclude that the division of comets into two polarimetric classes with one class having in the visual wavelength range a maximum polarization less than 20% is caused by ignoring the contribution of molecular emission and therefore is an artifact. Whether the comet displays a strong silicate feature (i.e. its dust grains are small) or not, the dust polarization is high.

Lumière diffusée par les particules solides éjectées du noyau de la comète 81P/Wild 2

Comet 81P/Wild 2, target of the Stardust mission, has been observed in 1997, through an imaging polarimetry technique. Intensity and polarization images, retrieved for 9 000 to 26 000 km wide fields, imply a value of the decrease of the intensity with increasing distance to the nucleus, and a decrease of the polarization in the inner coma, in agreement with previous observations of other comets. The averaged polarization values have been determined for the first time on this comet. The results suggest that it could belong to the class of comets with a low polarization at large phase angles and an absence of silicate emission features.

McDonald Observatory Spectral Observations of Comet 19P/Borrelly

We report on spectroscopic observations of the Deep Space 1 comet target, 19P/Borrelly. These observations were obtained during 1981, 1987, and 1994 at McDonald Observatory. We compute column densities for eight bands at a variety of positions within the coma and use these data and a Haser model in order to derive production rates for the gas. With these production rates, we show that Borrelly is a member of the carbon-chain molecule “depleted” class of comets. We also derive a measure of the dust in the coma ( Afρ) and show that this is a moderately dusty comet. We see, for the first time, a hint that the ratio C 3 and CH to CN production may vary with heliocentric distance.