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The study focused on the elemental abundance of two different comets. These comets were observed at an energy range of (100-10000) eV. The X-ray emission spectrum was analyzed and the results showed that comet C/1999 S4 (LINEAR) from the Oort cloud region (long-period) and comet 9p/Tempel 1 from the Kuiper Belt region (short-period) had the highest abundances of the different elements. The ds9 program used data from NASA's Chandra analysis to show the spectra of these comets and analyze their elements. The results showed that some elements were similar in all comets, such as (Carbon (C), Oxygen (O), Neon (Ne), and Silicon (Si)). While others varied from one comet to another, such as (Magnesium (Mg) and Chlorine (Cl)) elements which appeared in the C/1999 S4 (LINEAR) comet, and (Aluminum (A) and Phosphors (P)) elements which appeared in the 9P/Tempel 1 comet. This is due to these comets' areas of presence, where the elements of comets can be classified through their areas of presence. [ABSTRACT FROM AUTHOR]

Comets are the primitive planetesimals left in the solar system. Studying the evolution of comet nucleus is of great significance for understanding the formation and evolution history of other celestial bodies in the solar system. Under the action of solar radiation, the volatile components of comets sublimate and drive the dust movement, resulting in the loss of comet nucleus material. Therefore, the activity of comet nucleus affects the surface morphology and even the overall shape evolution. The orbit data were obtained from IAU (International Astronomical Union) MPC (Minor Planet Center), and the spin and precession of comet nucleus were taken into account. The shape evolution model of Mass loss-driven shape evolution model (MONET) was used to simulate the short period comet. The distribution of solar radiation energy and surface erosion depth of short-period comet 1P/Halley, 9P/Tempel 1, 19P/Borrelly, 67P/C-G (Churyumov-Gerasimenko), 81P/Wild 2, and 103P/Hartley 2 in one orbital period is calculated. Combined with its dynamic parameters, the effects of rotation, precession, and revolution on the sublimation distribution of surface water ice and the possibility of causing the difference in erosion between north and south are discussed. [ABSTRACT FROM AUTHOR]

Background Sexually transmitted infections (STIs) are currently the highest risk factor for transmitting HIV infection. The incidence of HIV and STIs increase every year and there are still many obstacles for People Living with HIV/AIDS (PLWHA) to get access to care and treatment. Since the WHO declared the COVID-19 pandemic and the implementation of regional quarantine and social distancing, the mobilization of people who should receive health services, including people with HIV and STIs, has decreased. These circumstances can neither achieve the Getting to Zeros program nor the triple elimination program. Currently, there are no reports on the impact of the COVID-19 pandemic on services and coverage of STIs and HIV in Indonesia. This study aimed to determine the impact, especially in Sleman Regency, Yogyakarta. Methods This epidemiological survey was conducted with a retrospective design and used secondary data. Restrictions on community mobility were implemented to prevent the spread of COVID-19 starting in April 2020. Data were collected from three hospitals and three primary health care (PHCs) in Sleman Regency, Yogyakarta, Indonesia, with STIs and HIV services, namely Dr. Sardjito Hospital, UGM Academic Hospital, Yogyakarta, Sleman Regional General Hospital, Tempel 1 Primary Health Care, Depok 3 Primary Health Care and Mlati 1 Primary Health Care. Data came from the registry at the research sites. The data obtained were tabulated and presented in the form of a table and analyzed descriptively. Results There was a decrease in patient visits to STIs and HIV services before and during the COVID-19 pandemic, by 34.48% and 0.23%, respectively. For laboratory examinations related to the diagnosis of STIs, there were variations in changes, whereby gonorrhea examinations decreased by 49.77%, examinations for detecting genital warts increased by 42.86%, VDRL examinations decreased by 40.22%, TPHA examinations decreased by 22.54% and HIV tests decreased by 4.12% in the period during the COVID-19 pandemic. For the number of visits by patients taking ARVs, there was an increase of 11.6% during the COVID-19 pandemic compared to before the COVID-19 pandemic. In laboratory examinations related to the triple elimination program in pregnant women, there were changes, namely in hepatitis B examination, there was an increase of 4.72%, HIV examination, a decrease of 1.54% and syphilis examination, there was a decrease of 1.15%. Conclusion The COVID-19 pandemic has impacted some services related to STIs and HIV. Further research on a broader scale is needed to confirm the extent of the impact. Strategies to improve the examination and management of STIs and HIV cases must always be prepared and their effectiveness evaluated in their implementation during this pandemic or in the event of other disease outbreaks in the future. [ABSTRACT FROM AUTHOR]

With the discovery of 1I 'Oumuamua and 2I Borisov, interstellar objects (ISOs) have been thrust into the forefront of planetary science, and the robotic exploration of ISOs is now of significant interest. With current propulsion technology, rendezvous with these objects is likely infeasible, and thus the maximum science return results from a combination of flyby spacecraft and impactor spacecraft, as demonstrated by the Deep Impact encounter with comet Tempel 1. Interstellar objects by nature have hyperbolic orbits and pass through the inner solar system at extreme velocities, which presents several unique challenges to navigation. This paper first establishes the possible encounter space intercepts with ISOs may present. We then evaluate the ability for intercepting spacecraft to navigate to ISOs and autonomously track/impact targets across the possible encounter space, depending on key navigation hardware such as camera and attitude determination system. • Rapid response spacecraft to interstellar objects encounter high solar phase angles. • High relative velocities severely limit ground-in-the-loop navigation accuracies. • Autonomous navigation can enable successful close flybys and tracking. • Autonomous navigation enables impactor guidance, though limited by high phase angles. [ABSTRACT FROM AUTHOR]

The aim of this research was to develop an enrichment book of colloid industry products as a source of literacy and to determine the quality of this book. The approach used in this study was Design-Based Research, which included four phases of development: 1) a questionnaire about needs was filled in by 5 teachers and 83 students; 2) the book was developed using CorelDraw X8 software and a literature search was conducted of online articles, journals and other supporting books; 3) cycles of testing were conducted, in which three experts and three peer reviewers assessed the book, and several revisions were produced; and 4) reflection and final evaluation were conducted, in which 5 teachers and 20 students from SMA N 2 Sleman, SMA N 2 Yogyakarta, SMA 1 Tempel, and MAN 3 Sleman assessed the substance, presentation, language and graphics of the book. Through this process, an enrichment book of colloidal industry products titled "Proses Pembuatan Koloid di Industri untuk SMA/MA Kelas XI" was produced. The book received a score 62.8 out of a maximum score of 70, which corresponded to a rating of 'very good quality'. [ABSTRACT FROM AUTHOR]

A circumstellar disk that surrounds a star is composed of gas, dust, and rocky objects that are in orbit around it. Around infant stars, this disk can act as a source of material that can be used to form planetesimals, which can then accrete more material and form into planets. Studying the mineral composition of these disks can provide insight into the processes that created our solar system. The purpose of this paper is to analyze the mineral composition of these disks by using a newly created python package, Min-CaLM. This package determines the relative mineral abundance within a disk by using a linear regression technique called non-negative least square minimization. The circumstellar disks that are capable of undergoing compositional analysis must have a spectrum with both a detectable mid-infrared excess and prominent silicate features. From our sample, there are only eight debris disks that qualify to be candidates for the Min-CaLM program. The mineral compositions calculated by Min-CaLM are then compared to the Tholen asteroid classification scheme. HD 23514, HD 105234, HD 15407A, BD+20 307, HD 69830, and HD 172555 are found to have a compositions similar to that expected for C-type asteroids, TYC 9410-532-1 resembles the composition of S-type asteroids, and HD 100546 resembles D-type asteroids. Min-CaLM also calculates the mineral compositions of the comets Tempel 1 and Hale-Bopp, and they are used as a comparison between the material in our early solar system and the debris disk compositions. [ABSTRACT FROM AUTHOR]

On approach to comet 9P/Tempel 1, Deep Impact observed about one dozen natural outbursts. One of the largest occurred on 2 July 2005 and was also captured by Deep Impact's infrared spectrometer, HRI-IR. HRI-IR operates between 1.05 and 4.86 µm, allowing it to detect H 2 O (2.67 µm) and CO 2 (4.27 µm) emission bands simultaneously. In the hours leading up to the outburst, both H 2 O and CO 2 behaved quiescently, consistent with previously published studies. During the outburst, CO 2 abundance increased by 40% while H 2 O abundance stayed constant. No additional species were detectable during the outburst. The distribution of CO 2 during the outburst is correlated with that of the dust, observed at the same time in the visible. The abundance of CO 2 returned to quiescent levels within 3.6 h of outburst onset. A slight enhancement in H 2 O was observed well after the outburst, though this does not appear to be correlated with the outburst. From this analysis, it is likely that CO 2 was a driver of the 2 July 2005 outburst and that H 2 O was not. [ABSTRACT FROM AUTHOR]

The paper presents experimental studies on the degassing of porous ice and porous mixtures of ice and sand in a vacuum. The study aims to find the relationship between the surface recession rate and the subsurface temperature gradient as well as the granulation and composition of the material. We propose an empirical equation tested on samples with a mass fraction of non-volatile material to ice in the range of 0–3.65. Based on the proposed equation, calculations were carried out, which indicate the possibility of landslides on the inclined areas on the surface of comet 9P/Tempel 1. • We investigated the surface recession rate of ice–sand mixtures in vacuum. • Investigated was the influence of the subsurface temperature gradient. • Empirical equations were tested using the results of measurements. [ABSTRACT FROM AUTHOR]

We attempt to answer two questions concerning the impacts of stream meteoroids on the nuclei of Comets 9P/Tempel 1 and 81P/Wild 2: firstly, how many streams cross the orbits of both comets and, secondly, what is the index of the differential mass distribution of impactors, s , when we assume that a prevailing number of the craters on the surfaces of cometary nuclei were created by stream meteoroids? We found that 110 and 129 potential streams originating from comets likely cross the orbits of 9P and 81P, respectively (and 103 potential streams cross the orbit of 1P/Halley, for comparison). If we consider the more compact streams originating from asteroids, the 9P and 81P pass through such streams 15 664 and 65 368 times. Neither these large numbers of passages imply, however, enough large impactors to excavate the whole observed variety of craters on studied comets. For all craters on 9P and 81P, s = 2.09 ± 0.01 and s = 2.25 ± 0.03 , respectively. The craters on 81P seem to be, however, excavated by the impactors from four discernible sources. For two numerous enough sources we find s = 5.6 ± 0.2 and s = 5.2 ± 0.5 . The difference between the indices for the set of all craters and the sets of their partial groups obviously implies an unknown cosmogonic consequence. [ABSTRACT FROM AUTHOR]

We analyzed Deep Impact High Resolution Instrument (HRI) images acquired within the first seconds after collision of the Deep Impact impactor with the nucleus of comet 9 P/Tempel 1. These images reveal an optically thick ejecta plume that casts a shadow on the surface of the nucleus. Using the 3D radiative transfer code HYPERION we simulated light scattering by the ejecta plume, taking into account multiple scattering of light from the ejecta, the surrounding nuclear surface and the actual observational geometry (including an updated plume orientation geometry that accounts for the latest 9 P/Tempel 1 shape model). Our primary dust model parameters were the number density of particles, their size distribution and composition. We defined the composition through the density of an individual particle and the ratio of its material constituents, which we considered to be refractories, ice and voids. The results of our modeling indicate a dust/ice mass ratio for the ejecta particles of at least 1. To further constrain the parameters of the model, we checked for consistency between the ejecta mass resulting from our modeling with the ejecta mass estimated by the crater formation modeling. Constraining the particle size distribution by results of other studies of the Deep Impact ejecta, we find the number density of ejecta particles equal to ∼104 particles/cm3 at the base of the plume. [ABSTRACT FROM AUTHOR]

The article discusses the European Space Agency's (EPA's) Rosetta spacecraft. Topics include Rosetta's rendezvous with comet 67P/Churyumov-Gerasimenko, the composition of 67P, the search for a suitable site to drop the Philae lander to the comet's surface, and clues to how 67P’s jets of gas and dust originate from the U.S. National Aeronautics and Space Administration's (NASA's) Stardust-NExT mission, which flew past comet Tempel 1 in 2001. INSET: Touch and go.

Abstract: Re-calibrated near-infrared spectroscopy of the resolved nucleus of Comet 9P/Tempel 1 acquired by the Deep Impact spacecraft has been analyzed by utilizing the post-Stardust-NExT nucleus shape model and spin pole solution, as well as a novel thermophysical model that explicitly accounts for small-scale surface roughness and thermal inertia. We find that the thermal inertia varies measurably across the surface, and that thermal emission from certain regions only can be reproduced satisfactory if surface roughness is accounted for. Particularly, a scarped/pitted terrain that experienced morning sunrise during the flyby is measurably rough (Hapke mean slope angle ∼45°) and has a thermal inertia of at most 50Jm−2 K−1 s−1/2, but probably much lower. However, thick layered terrain and thin layered terrain experiencing local noon during the flyby have a substantially larger thermal inertia, reaching 150Jm−2 K−1 s−1/2 if the surface is as rough as the scarped/pitted terrain, but 200Jm−2 K−1 s−1/2 if the terrain is considered locally flat. Furthermore, the reddening of the nucleus near-infrared 1.5–2.2μm spectrum varies between morphological units, being reddest for thick layered terrain (median value 3.4%kÅ−1) and most neutral for the smooth terrain known to contain surface water ice (median value 3.1%kÅ−1). Thus, Comet 9P/Tempel 1 is heterogeneous in terms of both thermophysical and optical properties, due to formation conditions and/or post-formation processing. [Copyright &y& Elsevier]

Abstract: Recent spacecraft encounters with Jupiter Family Comets have revealed markedly diverse surface morphologies: Wild 2 is dominated by steep-walled and flat-floored depressions, Tempel 1 is relatively smooth and exhibits evidence for flows and layering, while Hartley 2 is bi-lobed with knobby terrain at its ends and a much smoother terrain in its middle. This diversity of surface morphologies has been interpreted as an evolutionary sequence (Belton, M.J.S. [2010]. Icarus 210, 881–897) where Jupiter Family Comets evolve from Wild 2 morphology, then to Tempel 1 morphology, and finally to Hartley 2 morphology. We propose instead that the diversity of surface morphology reflects geologic processing with diverse outcomes. In addition to impact cratering, we consider surface modification driven by the cometary activity which is responsible for gas and dust production. We consider eolian erosion that may be driven by the outflow of cometary vapor, making use of information from wind tunnel experiments and in situ studies of eolian erosion on Mars. We adopt the model of van der Waals cohesion recently proposed by Scheeres et al. (Scheeres, D., Hartzell, C., Sanchez, P., Swift, M. [2010]. Icarus 210, 968–984) and find that the average CO2 vapor outflow flux at Hartley 2 of 0.95×1017 cm−2 s−1 implies wind speeds sufficient to mobilize particles of 10cm size even close to the icy reservoirs where the vapor is evolved, below the surface. We suggest that particles are mobilized and entrained in flows within sub-surface outflow channels, emerging to be readily lifted into the coma, and fragmenting in the process. Although water production from Hartley 2 is greater, most of it is evolved in the coma from icy particles and does not contribute to eolian erosion of the nucleus. On the other hand, the much lower vapor outflow flux at Tempel 1 of 4×1014 cm−2 s−1 is insufficient, in the present model, to mobilize particles but is consistent with generating repeated fluidization episodes. The Wild 2 case is intermediate, with average outflow flux 7×1016 cm−2 s−1 which would be, in our model, sufficient to support eolian erosion. The steep-walled, flat-floor depressions on Wild 2 may have originated as impact features but have been subsequently modified by eolian erosion causing slope recession. We do not have definitive evidence to discriminate between an evolutionary sequence and diverse geologic outcomes, but we suggest future in situ observations at comets that may do so. [Copyright &y& Elsevier]

Abstract: We present results from our study of the Stardust-NExT NAVCAM images of Comet 9P/Tempel 1, in which we analyze the dust coma and derive the locations and directions of 11 isolated jets detected around closest approach. Seven of the jets form a cluster that is associated with terraced terrain near the equator. Other jets arise from the nightside of the nucleus, having been in darkness for as long as 4h, indicating that thermal lags continue to drive activity long after sunset. We compare the coma features observed here to those seen during the Deep Impact encounter on the previous apparition, and argue that much of the isolated jet activity is associated with steep slopes and the edges of smooth areas. We estimate that the cluster of jets produces 7–20% of the total dust in the coma, indicating that isolated sources play a significant role in the comet’s activity. We measured an average dust production rate A(α)fρ =42±6cm at an approach phase angle of 79°, corresponding to a dust mass loss of approximately 264kgs−1. Our analysis also indicates that the Stardust-NExT spacecraft did not pass through any dust jets during the flyby. [Copyright &y& Elsevier]

Abstract: The photometric properties of the nucleus of Comet 9P/Tempel 1 as modeled from the Stardust-NExT images agree with those reported by Li et al. (Li, J.-Y. et al. [2007a]. Icarus 187, 41–55; Li, J.-Y., A’Hearn, M.F., McFadden, L.A., Belton, M.J.S. [2007b]. Icarus 188, 195–211) from Deep Impact images. No significant changes are detectable by comparing the two image-sets taken one comet year apart. The overall photometric variations on the ∼70% of the surface of Tempel 1 observed by Deep Impact and Stardust-NExT are small, with albedo variations of ±10% full-width-at-half-maximum and non-detectable variations in phase function and surface roughness. Some bright surface albedo features visible in the outbound images have an albedo about 25% higher than that of surrounding area. No bright albedo features similar to those ice patches reported by Sunshine et al. (Sunshine, J.M., et al. [2006]. Science 311, 1453–1455) are seen on the outbound side, which was not imaged by DI. The similar global photometric properties among cometary nuclei may indicate that these properties are dominated by cometary activity that results in constant resurfacing on comets. Tiny amounts of ice concentration on their surface can significantly change the local photometric properties. [Copyright &y& Elsevier]

Abstract: The nucleus of comet Tempel 1 has been investigated at close range during two spacecraft missions separated by one comet orbit of the Sun, 5½years. The combined imaging covers ∼70% of the surface of this object which has a mean radius of 2.83±0.1km. The surface can be divided into two terrain types: rough, pitted terrain and smoother regions of varying local topography. The rough surface has round depressions from resolution limits (∼10m/pixel) up to ∼1km across, spanning forms from crisp steep-walled pits, to subtle albedo rings, to topographic rings, with all ranges of morphologic gradation. Three gravitationally low regions of the comet have smoother terrain, parts of which appear to be deposits from minimally modified flows, with other parts likely to be heavily eroded portions of multiple layer piles. Changes observed between the two missions are primarily due to backwasting of scarps bounding one of these probable flow deposits. This style of erosion is also suggested by remnant mesa forms in other areas of smoother terrain. The two distinct terrains suggest either an evolutionary change in processes, topographically-controlled processes, or a continuing interaction of erosion and deposition. [Copyright &y& Elsevier]

Abstract: The Deep Impact spacecraft flew by Comet 103P/Hartley 2 on November 4th, 2010 (EPOXI mission) and Comet 9P/Tempel 1 on July 4th, 2005 (Deep Impact mission). During the two flybys, spatially resolved infrared (1.05–4.8μm) spectra of the surface of the nucleus were acquired by the HRI-IR instrument. The analysis of these two data sets, obtained by the same instrument, offers a unique opportunity to understand, compare and contrast the surface thermal properties of these two comets. For this paper, we use spectral cubes with a spatial resolution of 30m/pixel to 40m/pixel for Hartley 2 and 160m/pixel for Tempel 1. We focus our analysis on the color, temperature, thermal inertia and roughness of the nucleus. The two comets have the same color, moderately red, with an average slope of 3.0±0.9% per kÅ to 3.5±1.1% per kÅ. There are very small variations of the color across the surface, except for regions with water ice that are neutral to blue, and two dark spots with redder (4.5±1.4% per kÅ) materials on Hartley2. The nucleus thermal emission at all resolved spatial scales differs from that of a gray body with an infrared emissivity of 0.9–1.0, the discrepancy being more important for larger incidence angles. Moreover, the color temperature of Comets Hartley 2 and Tempel 1 is relatively homogeneous across the surface and does not vary strongly with incidence angle. These two effects mainly result from surface roughness and associated projected shadows. From the temperature rise on the morning terminator, we derive a thermal inertia lower than 250W/K/m2/s1/2 for Hartley2 and lower than 45W/K/m2/s1/2 for Tempel1 (3σ upper limits). For Hartley2 and Tempel1, the temperature of the regions with exposed water ice is more than 100K above the sublimation temperature of water ice (∼200K). This observation indicates that the thermal emission is dominated by dust, and that water ice is not intimately mixed with dust at the scale of observation, with water ice patches at the meter or sub-meter scale. [Copyright &y& Elsevier]

Abstract: We describe three methods for determination of the impact point of the Deep Impact Impactor on Comet 9P/Tempel 1, and the probable errors associated with each method. From this analysis it appears that the three methods give results that are consistent within their probable errors. [Copyright &y& Elsevier]

Abstract: The Dust Flux Monitor Instrument (DFMI) on the Stardust and Stardust-NExT missions measured impacts from coma dust particles with masses from ∼10−15 to >10−6 kg using two kinds of sensors – one based on polyvinylidene fluoride (PVDF) thin films and the other on acoustic detectors (ACs) mounted on the front and second layers of the Whipple Bumper Shield. At the higher encounter speed of 10.9kms−1 at Comet 9P/Tempel 1 compared with 6.12kms−1 at 81P/Wild 2 encounter, the mass sensitivity of DFMI sensors increased by between a factor of 2 and 12 (depending on the sensor subsystem), but the spatial resolution (⩾1.09km) decreased to approximately a half. The coma of Comet Tempel 1 exhibits highly non-uniform spatial distribution of dust, as found at comet Wild 2, with bursts of impacts of up to 1000 particles over km scales near closest approach surrounded by void regions of many kilometers with no impacts. These data are consistent with passage through clouds of particles resulting from fragmentation of larger aggregates emitted from the nucleus. These fragmentation products dominate the total dust production of small particles, with only a small contribution likely from direct emission from the nucleus. The derived overall mass distribution is similar to that found at comet Wild 2 with the total mass dominated by large particles. The average cumulative mass index α =0.65±0.08 (where the particle flux is defined by ϕ (>m)= km − α ) but a better fit is obtained with α =0.85±0.08 for particle masses below 10−10 kg and a significantly lower value for higher masses. [Copyright &y& Elsevier]

Abstract: We consider the origin of ∼380 quasi-circular depressions (pits) seen to be distributed in a broad band across the surface of 9P/Tempel 1 and show that possibly ∼96% may be due to outburst activity. Of the rest, <4%, are probably due to a mix of cryo-volcanic collapse events and collisional impacts with asteroidal material. We estimate the mass ejected during the June 14, 2005, mini-outburst on 9P to be in the range (6–30)×104 kg and find that the resulting pit should have a diameter in the range 10–30m. Published locations of mini-outbursts are revised to account for changes in the nucleus shape, rotation rate, and rotation pole that have resulted from observations made during the Stardust-NExT mission. Both of these locations are found to fall in, or on the edge of, the band of pits that encircles the nucleus. We have identified features in high-resolution images near one of these locations as the possible places of origin of the mini-outbursts. These features show close packing of multiple pits in the appropriate diameter range. We consider the distribution of pit diameters and show that the largest pits follow a power–law with exponent −2.24±0.09. Using the June 14, 2005, mini-outburst and the Deep Impact crater to provide a calibration, we establish empirical relationships between pit diameter, D, the total outburst energy, E, and the visual magnitude change, Δm abs, which is the visual amplitude of the outburst referenced to a standard initial brightness. We find Log10 D ∼0.107(±0.004)Δm abs +1.3(±0.4) and Log10 E ∼0.32(±0.01)Δm abs +10.1(±1.2) where the uncertainties represent the range of values for the coefficient rather than formal error. We apply these approximate relationships to the mega-outburst on 17P/Holmes and predict that it left a pit-like scar on the surface with a diameter in the range 160–1300m, that the total energy released was in the range 7×1012–3×1015 J, and that between 6×107 and 1.3×1011 kg of material was ejected from the surface. While these predictions are crude they encompass, particularly near the upper end of the range, the results on kinetic energy release and mass loss found by Reach et al. (Reach, W.T., Vaubaillon, J., Lisse, C.M., Holloway, M., Rho, J. [2010]. Icarus 208, 276–292) based on IR observations of 17P. [Copyright &y& Elsevier]

Abstract: Observations from the second encounter of Comet 9P/Tempel 1 by the Stardust-NExT spacecraft provide an improved shape model and rotational pole for the nucleus (Thomas, P.C. et al. [2012]. Icarus 222, 453–466) that allows us to greatly improve our knowledge of its rotational evolution beyond that outlined earlier in Belton et al. (Belton, M.J.S. et al. [2011]. Icarus 213, 345–368). Model light curves are shown to fit observations at both perihelia with a single pole direction indicating that polar precession during a single perihelion passage is small. We show that the rotational phasing associated with observations taken far from perihelion in the previous work was incorrectly assessed by approximately half a cycle leading us to a significant reassessment of the evolution of the non-gravitational torques acting on the nucleus. We present an updated spin rate profile (torque model) for the 2005 perihelion passage and show that retardation of the spin rate well before perihelion is no longer a required feature. With the exception of the spin rate before the 2000 perihelion passage, the evolution of rotational rates through the three most recent perihelion passages is largely unaffected as is the prediction of the rotational phase of the comet’s nucleus at the Stardust-NExT near-perihelion encounter. We find a spin rate of 209.4±0.01°/d likely applies in the quiescent period before the 2000 perihelion, a 0.2% change, and that the rotational period shortened by 12.3±0.2min during the 2000 perihelion passage. We present an analysis of Stardust-NExT time-series photometry that yields a spin rate near 213.3±0.8°/d at the time of encounter. An application of the 2005 torque model suggests that, while roughly similar, the torques were probably weaker during the 2011 perihelion passage. [Copyright &y& Elsevier]

Abstract: The Stardust-NExT (SdN) mission returned to Comet 9P/Tempel-1 and viewed the site of the Deep Impact (DI) collision just over one comet year later. Comparisons between pre-impact images from the ITS camera on the DI probe and SdN images reveal a 50m-diameter crater surrounded by a low rim about 180m in diameter. The removal of a small mound uprange (but offset from the trajectory) from the impact site can be related to changes in the evolution of ejecta. A narrow (6°) gap in the ejecta curtain downrange indicates that a ridge extending from the impact-facing scarp downrange interrupted the final stages of cratering in one small region. Together, these observations indicate that the DI excavation crater diameter was about 200m (±20m), a value consistent with the ejected mass derived from Earth- and space-based observations with the assumption that this mass represents only 10–20% of the total ejected mass. As a result, the DI crater visible today is consistent with either a larger transient crater, which collapsed, or a central crater of a nested crater resembling an inverted sombrero. The latter alternative would be expected from a layered target: a loose particulate surface about 1–2m deep over a slightly more competent substrate. [Copyright &y& Elsevier]

Abstract: In this work, we describe a detailed study of the Deep Impact (DI) collision site on Comet 9P Tempel 1 as imaged by the Stardust-NExT spacecraft in February of 2011. This investigation reveals a tentatively identified, barely resolvable, shallow impact crater located at the previously identified impact site, 49±12m in diameter; surrounded by an area of slightly brightened material marking a potential ejecta blanket 85–120m in diameter. Assuming that this crater identification is correct, we use this diameter to place further constraints on the surface material struck by the DI impactor to yield crater scaling-law constants of μ =0.45±0.05 (exponential constant), K 1 =0.15±0.05 (linear proportionality constant), and (effective target strength) utilizing the expressions and nomenclature of Holsapple (Holsapple, K.A. [1993]. Annu. Rev. Earth Planet. Sci. 21, 333–373). These material constants are roughly analogous to the material properties of a lightly-packed, ‘dry’ mountain snow. Additional modeling yields refined values for the total ejected mass produced by the DI event of 1.2×106 kg (5.4×105–2.6×106 kg), with 60% ± 20% of that mass ejected at greater than the comet’s escape velocity of 1.4m/s, and producing a relatively thin ejecta blanket with a thickness at the final crater rim of 2.7mm (0.5–13mm). These values are consistent with our previous analysis of the Deep Impact event’s ejecta behavior as seen from the DI flyby spacecraft, as well as the observations conducted by other Earth-orbiting and Earth-based telescopes. [Copyright &y& Elsevier]

Abstract: On February 14, 2011 Stardust-NExT (SN) flew by Comet Tempel 1, the target of the Deep Impact (DI) mission in 2005, obtaining dust measurements and high-resolution images of areas surrounding the 2005 impact site, and extending image coverage to almost two thirds of the nucleus surface. The nucleus has an average radius of 2.83±0.1km and a uniform geometric albedo of about 6% at visible wavelengths. Local elevation differences on the nucleus reach up to 830m. At the time of encounter the spin rate was 213° per day (period=40.6h) and the comet was producing some 130kg of dust per second. Some 30% of the nucleus is covered by smooth flow-like deposits and related materials, restricted to gravitational lows. This distribution is consistent with the view that the smooth areas represent material erupted from the subsurface and date from a time after the nucleus achieved its current shape. It is possible that some of these eruptions occurred after 1609 when the comet’s perihelion distance decreased from 3.5AU to the current 1.5AU. Much of the surface displays evidence of layering: some related to the smooth flows and some possibly dating back to the accretion of the nucleus. Pitted terrain covers approximately half the nucleus surface. The pits range up to 850m in diameter. Due to their large number, they are unlikely to be impact scars: rather they probably result from volatile outbursts and sublimational erosion. The DI impact site shows a subdued depression some 50m in diameter implying surface properties similar to those of dry, loose snow. It is possible that the 50-m depression is all that remains of an initially larger crater. In the region of overlapping DI and SN coverage most of the surface remained unchanged between 2005 and 2011 in albedo, photometric properties and morphology. Significant changes took place only along the edges of a prominent smooth flow estimated to be 10–15m thick, the margins of which receded in places by up to 50m. Coma and jet activity were lower in 2011 than in 2005. Most of the jets observed during the SN flyby can be traced back to an apparently eroding terraced scarp. The dust instruments detected bursts of impacts consistent with a process by which larger aggregates of material emitted from the nucleus subsequently fragment into smaller particles within the coma. [Copyright &y& Elsevier]

The 4050 Å band of C was observed with Keck/HIRES echelle spectrometer during the Deep Impact encounter. We perform a 2-dimensional analysis of the exposures in order to study the spatial, spectral, and temporal changes in the emission spectrum of C. The rotational population distribution changes after impact, beginning with an excitation temperature of ∼45 K at impact and increasing for 2 hr up to a maximum of 61±5 K. From 2 to 4 hours after impact, the excitation temperature decreases to the pre-impact value. We measured the quiescent production rate of C before the encounter to be 1.0×10 s, while 2 hours after impact we recorded a peak production rate of 1.7×10 s. Whereas the excitation temperature returned to the pre-impact value during the observations, the production rate remained elevated, decreasing slowly, until the end of the 4 hr observations. These results are interpreted in terms of changing gas densities in the coma and short-term changes in the primary chemical production mechanism for C. [ABSTRACT FROM AUTHOR]

ABSTRACT The distance between the pre-impact surface of Comet 9P/Tempel 1 and the upper border of the largest cavity excavated during the ejection of material after the collision of the impact module of the Deep Impact ( DI) spacecraft with the comet is estimated to be about 5-6 m if the diameter of the DI transient crater was about 150-200 m. The estimated distance is 4 m if the diameter was 100 m. This result suggests that cavities containing dust and gas under pressure and located a few metres below the surfaces of comets can be common. [ABSTRACT FROM AUTHOR]

The article focuses on cometary research and the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) unmanned space mission. It states EPOXI flew past comet Hartley 2 on November 4, 2010 and took photographs and spectrographic measurements. It comments that Hartley 2 has a small and active nucleus that is outgassing carbon dioxide which drags particles of ice out of the nucleus. It talks about the comet's surface geology and the average geometric albedo and on differences between Hartley 2 and the comet Tempel 1.

Time-variations in velocities and relative amount of observed particles (mainly icy particles with diameter m) ejected from Comet 9P/Tempel 1 are studied based on analysis of the images made by Deep Impact (DI) cameras during the first 13 min after the collision of the DI impactor with the comet. Analysis of maxima or minima of plots of the time-variations in distances of contours of constant brightness from the place of ejection allowed us to estimate the characteristic velocities of particles at several moments in time, , of ejection after impact for s. Other approaches for estimates of the velocities were also used. All these estimates are in accordance with the same exponential decrease in velocity. The estimates of time-variations in the relative amount of ejected particles were also based on results of the analysis of time-variations in the size of the bright region of ejected material. At s, the morphology of the ejecta (e.g. the location and brightness of the brightest pixel) changed and the rate, , of ejection of observed material increased. Between 1 and 3 s after the impact and between 8 and 60 s after the impact, more small bright particles were ejected than expected from crater excavation alone. An outburst triggered by the impact could cause such a difference. The sharp (by a factor of 1.6) decrease in the rate of ejection at s could be caused by a decrease in the outburst that began at 10 s. Analysis of observations of the DI cloud and of the outbursts from some comets testifies in favour of the proposition that there can be large cavities, with material under gas pressure, below a considerable fraction of a comet's surface. Internal gas pressure and material in the cavities can produce natural and triggered outbursts and can cause splitting of comets. [ABSTRACT FROM AUTHOR]

Abstract: 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 image at least 25% of the nucleus seen by the Deep Impact spacecraft to better than 80m/pixel, and to image the crater made during the encounter, if possible. In total, ∼500 whole or partial nights were allocated to this project at 14 observatories worldwide, utilizing 25 telescopes. Seventy percent of these nights yielded useful data. The data were used to determine the linear phase coefficient for the comet in the R-band to be 0.045±0.001magdeg−1 from 1° to 16°. Cometary activity was observed to begin inbound near r ∼4.0 AU and the activity ended near r ∼4.6 AU as seen from the heliocentric secular light curves, water-sublimation models and from dust dynamical modeling. The light curve exhibits a significant pre- and post-perihelion brightness and activity asymmetry. There was a secular decrease in activity between the 2000 and 2005 perihelion passages of ∼20%. The post-perihelion light curve cannot be easily explained by a simple decrease in solar insolation or observing geometry. CN emission was detected in the comet at 2.43 AU pre-perihelion, and by r =2.24 AU emission from C2 and C3 were evident. In December 2004 the production rate of CN increased from 1.8×1023 mols−1 to Q CN =2.75×1023 mols−1 in early January 2005 and 9.3×1024 mols−1 on June 6, 2005 at r =1.53 AU. [Copyright &y& Elsevier]

Abstract: 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±0.005h) prior to the 2000 perihelion passage, 210.448±0.016°/dy (41.055±0.003h) for the interval between the 2000 and 2005 perihelion passages, 211.856±0.030°/dy (40.783±0.006h) from Deep Impact photometry just prior to the 2005 perihelion passage, and 211.625±0.012°/dy (40.827±0.002h) in the interval 2006–2010 following the 2005 perihelion passage. The period decreased by 16.8±0.3min during the 2000 passage and by 13.7±0.2min during the 2005 passage suggesting a secular decrease in the net torque. The change in spin rate is asymmetric with respect to perihelion with the maximum net torque being applied on approach to perihelion. The Deep Impact data alone show that the spin rate was increasing at a rate of 0.024±0.003°/dy/dy at JD2453530.60510 (i.e., 25.134 dy before impact), which provides independent confirmation of the change seen in the Earth-based observations. The rotational phase of the nucleus at times before and after each perihelion and at the Deep Impact encounter is estimated based on the Thomas et al. (Thomas et al. [2007]. Icarus 187, 4–15) pole and longitude system. The possibility of a 180° error in the rotational phase is assessed and found to be significant. Analytical and physical modeling of the behavior of the spin rate through of each perihelion is presented and used as a basis to predict the rotational state of the nucleus at the time of the nominal (i.e., prior to February 2010) Stardust-NExT encounter on 2011 February 14 at 20:42. We find that a net torque in the range of 0.3–2.5×107 kgm2 s−2 acts on the nucleus during perihelion passage. The spin rate initially slows down on approach to perihelion and then passes through a minimum. It then accelerates rapidly as it passes through perihelion eventually reaching a maximum post-perihelion. It then decreases to a stable value as the nucleus moves away from the Sun. We find that the pole direction is unlikely to precess by more than ∼1° per perihelion passage. The trend of the period with time and the fact that the modeled peak torque occurs before perihelion are in agreement with published accounts of trends in water production rate and suggests that widespread H2O out-gassing from the surface is largely responsible for the observed spin-up. [Copyright &y& Elsevier]

Abstract: 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 H2O through the porous mantle; Type II that is controlled by the localized and persistent effusion of super-volatiles from the interior; and Type III that is characterized by episodic releases of super-volatiles. The zonally averaged distribution of active area locations associated with Type II outflows over the four comets is calculated and we find that they are distributed randomly in latitude. In longitude, the distribution shows a marginal tendency for active areas to occur more frequently in the region near the ends of the long axis or, alternatively, a tendency to avoid the region close to the ends of the intermediate axis. Combining observations of filamentary structure with exploratory hydrodynamic calculations we find that Type II outflows are likely to be relatively cold laminar flows (Re<1000) of a mixture of CO2, CO and H2O that are highly collimated (6–10° full-cone angle) during the daytime as a result of being constrained by the ambient H2O atmosphere. We propose that they become visible as a result of the turbulent momentum flux at the base of the filamentary structure that causes the friable surface to release dust at a higher rate than in surrounding areas. We present evidence that indicates that geophysical flows occur on cometary nuclei other than 9P/Tempel 1 and discuss a possible scenario for the long-term evolution of cometary surfaces near the Sun. We conclude with an exposition of a cometary activity paradigm brought up-to-date with discoveries made with recent space missions, associated Earth-based investigations, and the results of this work. [Copyright &y& Elsevier]

Abstract: The pre-Deep Impact images of Comet Tempel-1 obtained at the Indian Astronomical Observatory are used to investigate the morphology of the dust coma of the comet. We show that the trajectory of a cometary grain under the influence of solar radiation pressure is a reliable diagnostic to estimate its initial velocity. Four main active regions at mean latitudes +45°±5°(D), 0°±5° (E),−30°±5°(A) and−60°±5°(F) are found to explain the morphology of the dust coma in the ground-based and published images obtained by the High Resolution Instrument(HRI) cameras aboard the Deep Impact flyby spacecraft. From a fit of the intensity distribution in the observed and the simulated images, we derive the fraction of the productivity of the active vents to the total dust emission of the comet to be 27%. Of this the southern source alone accounts for 19.8%. The grains are found to be ejected with a velocity distribution with an upper limit of 70±7ms−1. However, the broad region ‘A’ appears to eject slower grains with an upper limit of 24±2.5ms−1. This source, that is active throughout the cycle is likely to be driven by sublimation. We compute the dependence of the percentage contribution of the southern source on the heliocentric distance and show that this ratio varies over the apparition and reaches a maximum at around 260 days before perihelion. The published images of the nucleus of Comet Tempel-1 show significant departure from sphericity. Therefore, the torque exerted by the enhanced activity of the southern region may be significant enough to produce changes in the rotational state of the nucleus before each perihelion passage. [Copyright &y& Elsevier]

Abstract: From recent close encounters with Comets Wild-2 and Tempel 1 we learned that their surfaces are very rugged and no simple uniform layers model can be applied to them. Rather, a glaciological approach should be applied for describing their surface features and behavior. Such intrinsically rugged surface is formed in our large scale experiments, where an agglomerate of ∼200 μm gas-laden amorphous ice particles is accumulated to form a 20 cm diameter and few cm high ice sample. The density, tensile strength and thermal inertia of our ice sample were found to be very close to those found by Deep Impact for Comet Tempel 1: density 250–300 kg m−3 vs DI 350–400 kg m−3; tensile strength 2–4 kPa vs DI 1–10 kPa; thermal inertia 80 W K−1 m−2 s1/2 vs <100 W K−1 m−2 s1/2 and <50 W K−1 m−2 s1/2. From the close agreement between the thermal inertias measured in our ice sample, which had no dust coverage and that of Comet Tempel 1, we deduce that the low thermal inertia is an intrinsic property of the fluffy structure of the ice as a result of its low density, with an addition by the broken terrain and not due to the formation of a dust layer. Upon warming up of the ice, water vapor migrates both outward into the coma and inward. Reaching cooler layers, the water vapor condenses, forming a denser ice crust, as we show experimentally. We also demonstrate the inward and outward flow of water vapor in the outer ice layers through the exchange between layers of D2O ice and H2O ice, to form HDO. [Copyright &y& Elsevier]

Abstract: In this paper we analyze near-infrared thermal emission spectra of the spatially resolved nucleus of Comet 9P/Tempel 1 obtained by the NASA spacecraft Deep Impact. Maps of spectral reddening, the product between the beaming function and directional emissivity, as well as surface temperature are constructed. Thermophysical modeling is used to estimate the degree of small scale surface roughness and thermal inertia by detailed reproduction of the empirical temperature map. Mie and Hapke theories are used in combination with numerically calculated beaming functions to analyze the map and place constraints on composition and grain size of the surface material. We show that it is absolutely mandatory to include small scale surface roughness in thermophysical modeling of this object, since the resulting self heating is vital for reproducing the measured temperatures. A small scale self heating parameter in the range is common, but smoother areas where are also found. Contrary to models neglecting small scale surface roughness, we find that the thermal inertia of Comet 9P/Tempel 1 generally is high (1000–3000 J m−2 K−1 s−1/2), although it may be substantially lower (40–380 J m−2 K−1 s−1/2) in specific areas. We obtain a disk-averaged reddening of 3.5% kÅ−1, with statistically significant local variations around that value on a level. Vast regions appear covered by small (∼0.1 μm) highly absorbing grains such as carbon or iron-rich silicates. Other regions appear dominated by somewhat larger (∼0.5 μm) and/or less absorbing grains such as troilite or magnesium-rich silicates. Surface variations in reddening, roughness, thermal inertia, composition and/or grain size are moderately to strongly correlated to the locations of morphological units on the surface. The existence of morphological units with differing physical properties may be primordial, hence reflecting a diversity in the building block cometesimals, or resulting from evolutionary processes. [Copyright &y& Elsevier]

Abstract: We report on low-spectral resolution observations of Comet 9P/Tempel 1 from 1983, 1989, 1994 and 2005 using the 2.7 m Harlan J. Smith telescope of McDonald Observatory. This comet was the target of NASA''s Deep Impact mission and our observations allowed us to characterize the comet prior to the impact. We found that the comet showed a decrease in gas production from 1983 to 2005, with the decrease being different factors for different species. OH decreased by a factor 2.7, NH by 1.7, CN by 1.6, C3 by 1.8, CH by 1.4 and C2 by 1.3. Despite the decrease in overall gas production and these slightly different decrease factors, we find that the gas production rates of OH, NH, C3, CH and C2 ratioed to that of CN were constant over all of the apparitions. We saw no change in the production rate ratios after the impact. We found that the peak gas production occurred about two months prior to perihelion. Comet Tempel 1 is a “normal” comet. [Copyright &y& Elsevier]

Calibration of NASA’s Deep Impact spacecraft instruments allows reliable scientific interpretation of the images and spectra returned from comet Tempel 1. Calibrations of the four onboard remote sensing imaging instruments have been performed in the areas of geometric calibration, spatial resolution, spectral resolution, and radiometric response. Error sources such as noise (random, coherent, encoding, data compression), detector readout artifacts, scattered light, and radiation interactions have been quantified. The point spread functions (PSFs) of the medium resolution instrument and its twin impactor targeting sensor are near the theoretical minimum [∼1.7 pixels full width at half maximum (FWHM)]. However, the high resolution instrument camera was found to be out of focus with a PSF FWHM of ∼9 pixels. The charge coupled device (CCD) read noise is ∼1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to ∼1%. Spectrometer read noise is ∼2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to ∼10 DN at best. Wavelength mapping onto the detector is known within 1 pixel; spectral lines have a FWHM of ∼2 pixels. About 1% of the IR detector pixels behave badly and remain uncalibrated. The spectrometer exhibits a faint ghost image from reflection off a beamsplitter. Instrument absolute radiometric calibration accuracies were determined generally to <10% using star imaging. Flat-field calibration reduces pixel-to-pixel response differences to ∼0.5% for the cameras and <2% for the spectrometer. A standard calibration image processing pipeline is used to produce archival image files for analysis by researchers. [ABSTRACT FROM AUTHOR]

Abstract: We suggest that the regions of smooth terrain which were observed on Comet 9P/Tempel 1 by the Deep Impact spacecraft were formed by blowing ice grains in an outburst of gas from the comet interior. When gas is released from 10 to 20 m deep layers which were heated to 135 K, it is released quiescently onto the surface by individual conduits. If large amounts of gas are released, the drainage system cannot release them fast enough and wider interconnected channels are formed, leading to sudden outburst of gas. Instability triggering a sudden shift of flow is well known in subglacial drainage of water. The ballistic trajectory of the ice particles reach a distance of 3 km in the atmosphereless comet, whose gravity is 0.034 cm s−1, if ejected at an angle of 45° at a speed of 95 cm s−1. This speed is close to the speeds measured in laboratory experiments: 167, and 167 cm s−1, for particles of 0.3, 1000 and 14–650 μm, respectively. Blowing of ice grains can overcome the 1650 m long horizontal section of smooth terrain i1 (Fig. 1), whereas simple flow of material downhill would stop close to the foot of the hill. The ice particles at the end of their trajectory have a horizontal velocity component and this low velocity ballistic sedimentation would lead to formation of lineaments on the smooth terrain, like in solid-particulate volcanic eruptions. [Copyright &y& Elsevier]

Deep Impact successfully met its primary mission objective on 4 July 2005 when the smart impactor guided itself into the path of Comet 9P/Tempel 1. The mother flyby spacecraft then observed and recorded the breathtaking collision and subsequent plume development. Ground-based navigators targeted the prerelease trajectory using optical navigation image planning and data analysis, trajectory correction maneuver design and evaluation, and orbit determination using both radiometric and optical data. In-flight improvements to the Tempel 1 ephemeris were also a critical part of the overall navigation design and operations success. The achieved navigation accuracy established a new standard for comet encounters, and this difficult task taught several important lessons. This definitive Work provides a mission overview, summarizes the navigation requirements, compares the achieved navigation performance with a baseline design that reflects in-flight updates, and identifies operational procedures that may benefit future comet-bound navigators. [ABSTRACT FROM AUTHOR]

Abstract: Near-simultaneous R- and J-band photometric measurements of the short-period Comets 2P/Encke and the Deep Impact mission target 9P/Tempel 1 were obtained. The resulting colors are and for Encke and Tempel 1, respectively. Tempel 1''s color is redder than the solar color index of +0.76. The Tempel 1 observations directly detected the nucleus while the Encke observations likely suffered from coma contamination. [Copyright &y& Elsevier]

Comets spend most of their life in a low-temperature environment far from the Sun. They are therefore relatively unprocessed and maintain information about the formation conditions of the planetary system, but the structure and composition of their nuclei are poorly understood. Although in situ and remote measurements have derived the global properties of some cometary nuclei, little is known about their interiors. The Deep Impact mission shot a projectile into comet 9P/Tempel 1 in order to investigate its interior. Here we report the water vapour content (1.5 × 1032 water molecules or 4.5 × 106 kg) and the cross-section of the dust (330 km2 assuming an albedo of 0.1) created by the impact. The corresponding dust/ice mass ratio is probably larger than one, suggesting that comets are ‘icy dirtballs’ rather than ‘dirty snowballs’ as commonly believed. High dust velocities (between 110 m s-1 and 300 m s-1) imply acceleration in the comet's coma, probably by water molecules sublimated by solar radiation. We did not find evidence of enhanced activity of 9P/Tempel 1 in the days after the impact, suggesting that in general impacts of meteoroids are not the cause of cometary outbursts. [ABSTRACT FROM AUTHOR]