The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The disk-resolved flyby images of the nucleus of Comet 81P/Wild 2 collected by Stardust are used to perform a detailed study of the photometric properties of this cometary nucleus. A disk-integrated phase function from phase angle 11° to about 100° is measured and modeled. A phase slope of 0.0513±0.0002 mag/deg is found, with a V-band absolute magnitude of 16.29±0.02. Hapke’s photometric model yields...
Arecibo radar imagery of Comet 8P/Tuttle reveals a 10-km-long nucleus with a highly bifurcated shape consistent with a contact binary. A separate echo component was also detected from large (>cm-size), slow-moving grains of the type expected to contribute to the Ursid meteor stream.
This work is dedicated to the application to 67P/Churyumov-Gerasimenko of a new quasi-3D approach for non-spherically shaped comet nuclei with the aim to interpret the current activity of the comet in terms of initial characteristics and to predict shape and internal stratification evolution of the nucleus. The model is applied to differently shaped nuclei taking into account the characteristics of...
Our work was inspired by the recent brightening of Comet 17P/Holmes. The recently observed increase in brightness of this comet was correlated with emission of dust, probably larger in mass than the dust mantle of the nucleus. We analyzed the hypothesis that the comet can eject a large mass of dust due to non-uniform crystallization of amorphous water ice. For this purpose, we simulated the evolution...
An explosion on Comet 17P/Holmes occurred on 2007 October 23, projecting particulate debris of a wide range of sizes into the interplanetary medium. We observed the comet using the mid-Infrared Spectrograph (5–40μm), on 2007 November 10 and 2008 February 27, and the imaging photometer (24 and 70μm), on 2008 March 13, on board the Spitzer Space Telescope. The 2007 November 10 spectral mapping revealed...
The rotation period derived by Mueller and Samarasinha (Mueller, B.E.A., Samarasinha, N.H. [2002]. Earth Moon Planets 90, 463–471) of the Deep Space 1 (DS1) mission target, Comet 19P/Borrelly, using ground-based data from July 28 to August 1, 2000, is improved by two orders of magnitude. This precision is reached in a multistep process.Combining all available ground-based data in 2000 decreases the...
We present thermal evolution calculations of inhomogeneous asymmetric initial configurations of a spherical model of Comet 67P/Churyumov–Gerasimenko, using a fully 3-dimensional numerical code. The initial composition is amorphous H 2 O ice and dust, in a “layered-pile” configuration, where layers differing in ice/dust ratio and thermal properties extend over a fraction of the surface area...
The properties of 50 jet and jet-filament outflows from 27 active areas observed on the four comet nuclei that have been visited by spacecraft (1P/Halley, 19P/Borrelly, 81P/Wild 2, and 9P/Tempel 1) are investigated and we propose a taxonomic categorization in which there are three types of active areas: Type I that is dominated by the sublimation of H 2 O through the porous mantle; Type II...
Comet 133P/Elst-Pizarro, known to be a main-belt asteroid with a cometary activity, was observed with the near-infrared integral field spectrograph SINFONI at the 8.2-m Very Large Telescope in J, H, and K bands during its 2007 perihelion passage. The goal of these observations was to attempt detection of water ice absorption bands. We present here the details of the data processing, the results of...
The determination of the nuclear magnitudes of comets, and with it nuclear size frequency distributions, is strongly complicated by cometary activity. By now, only nuclear size frequency distributions for Jupiter Family comets are available, and they are still subject of uncertainties. For comets of other dynamical classes, nuclear magnitudes are known for only a few comets. The size frequency distributions...
An investigation of the activity of Comet C/1995 O1 (Hale-Bopp) with a thermophysical nucleus model that does not rely on the existence of amorphous ice is presented. Our approach incorporates recent observations allowing to constrain important parameters that control cometary activity. The model accounts for heat conduction, heat advection, gas diffusion, sublimation, and condensation in a porous...
We present observational data for Comet 9P/Tempel 1 taken from 1997 through 2010 in an international collaboration in support of the Deep Impact and Stardust-NExT missions. The data were obtained to characterize the nucleus prior to the Deep Impact 2005 encounter, and to enable us to understand the rotation state in order to make a time of arrival adjustment in February 2010 that would allow us to...
A model for the aggregation of size distribution of cometesimals (Gaussian or power law) into cometary nuclei is developed. Upon disruption induced by collisions, sticking and evolution of the tensile strength and density of the cometesimals by sintering processes are taken into account. The resulting cometary nuclei present specific internal structures that have been quantified to allow the comparison...
The evolution of the spin rate of Comet 9P/Tempel 1 through two perihelion passages (in 2000 and 2005) is determined from 1922 Earth-based observations taken over a period of 13year as part of a World-Wide observing campaign and from 2888 observations taken over a period of 50 days from the Deep Impact spacecraft. We determine the following sidereal spin rates (periods): 209.023±0.025°/dy (41.335±0...
Our knowledge about the physical processes determining the activity of comets were mainly influenced by several extremely successful space missions (Giotto, Deep Space I, Stardust, Deep Impact and EPOXI), the predictions of theoretical models and the results of laboratory experiments. However, novel computer models should not be treated in isolation but should be based on experimental results and...
Coagulation models assume a higher sticking threshold for micrometer-sized ice particles than for micrometer-sized silicate particles. However, in contrast to silicates, laboratory investigations of the collision properties of micrometer-sized ice particles (in particular, of the most abundant H 2 O-ice) have not been conducted yet. Thus, we used two different experimental methods to produce...
In this paper we review the relevant literature and investigate conditions likely to lead to melting of H 2 O ice, methanol (CH 3 OH) ice, ethane (C 2 H 6 ) ice and other volatile ices in cometary nuclei. On the basis of a heat balance model which takes account of volatiles loss, we predict the formation of occasional aqueous and hydrocarbon liquid phases in subsurface...
We present observations and analysis of the forbidden oxygen lines in Comets C/2006 W3 (Christensen) and C/2007 Q3 (Siding Spring) at heliocentric distances of 3.13 and 2.96AU, respectively. We obtained the observations using the ARCES echelle spectrometer, which is mounted on the Astrophysical Research Consortium 3.5-m telescope at Apache Point Observatory. We detected the 5577, 6300, and 6364Å atomic...
Upon discovery, in November of 1892, Comet 17P/Holmes was experiencing a very strong explosion, which repeated itself on an even greater scale in October of 2007. Using a numerical scheme, based on mass and energy conservation laws, a model is presented simulating the outbursting nature of Comet 17P/Holmes by regarding the comet as a stratified sphere. The model, adopting input parameters for physical...
We developed a thermophysical model for cometary nuclei, which is based upon the assumption that comets form by the gravitational instability of an ensemble of dust and ice aggregates. Under this condition, the tensile strength of the ice-free outer layers of a cometary nucleus can be calculated, using the dust–aggregate collision and adhesion model of Weidling et al. (Weidling, R. et al. [2012]....
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.