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Comets formed from the material surrounding the young Sun, about 4.6 billion years ago. After their formation, the nuclei were scattered and stored in their current reservoirs [1,2], where they remained mainly unaltered, preserving most of the chemical and physical properties linked to their formation site. Cometary nuclei contain a mix of various silicates (mainly olivine and pyroxene that can be found in the amorphous and/or crystalline form), organic refractory material and other minor elements [3]. Comet dust appears different from comet-to-comet, and partially different from the one observed in the interstellar medium [4]. These differences may correlate in principle with some of the processes that were in act in the protoplanetary disc at the time and in the region where the nuclei formed. A detailed study of the cometary dust can thus improve our understanding of the formation and evolution of matter in the early Solar System, and test the most recent theoretical models of cometary nuclei [5]. Mid-infrared spectroscopy in the wavelength range between 7 to 40 μm can give information on the temperature and chemical compostition of the dust, and help inferring dust grains size and structure [3,4,6]. Spectral maps of active comets in this spectral range allow measurements of the chemical and temperature variations within a large portion of the coma. If observed, these fluctuations can be in principle associated to different processes (e.g., fragmentation processes), and can help to put some constraints on the physical properties of the observed dust, more stringent than the ones retrieved just observing in proximity of the nucleus. The coma of 67P was mapped with the InfraRed Spectrometer (IRS) on board of the Spitzer telescope between the 28th and 30th of November, 2008. At the observing epochs, the comet was at about 1.65 au from the Sun and about 1.00 au from the spacecraft. The maps were taken using both the short-wavelength (7-14 μm) and the long-wavelength (14-38 μm) IRS spectrometers. We reduced the data using the official pipeline CUBISM [7] that performs all the basic reduction and calibration steps (i.e., background subtraction, bad pixels removal, flux calibration for extended sources comprising aperture correction and slit loss correction). The spectral cubes produced by CUBISM were re-sampled to eliminate some residual aliasing effects resulting from the reduction process, and spectral cubes from different settings (short and long wavelengths) were combined together. In this way, we were able to extract the full 7-38 μm spectrum for each pixel in a FOV of about 27”x38”. In general, we observe smoothed spectra and no signs of crystalline silicates; we identify clearly an amorphous silicate band around 11 μm. Smoothed spectra could be indicative of a low abundance of crystalline silicates or related to the presence of larger and/or less porous dust grains in the coma. The thermal analysis of the extracted spectra, performed with the model developed by [8], do no show any particular temperature variation, nor visible signs of fragmentation. Finally, we investigated the coma morphology, searching for the presence of jets and/or anisotropies. Acknowledgements: This work has received funding from the European Research Council (ERC) - program grant CAstRA, agreement ID 757390. Data were downloaded from the Spitzer Heritage archive, and collected under the program ID 50022, ’Creating Synergy Between Spitzer and Rosetta: The Coma of Comet 67P’, PI - M. Kelley. References: [1]. Gomes, R., et al., 2005, Nature, 435, 446 – [2]. Morbidelli, A., et al., 2007, AJ, 134, 1790 – [3]. Hanner, M. S., 1999, Space Science Reviews, 90, 99 – [4]. Wooden, D. H., et al., 2017, Phil. Trans. R. Soc. A 375 – [5]. Ciarniello, M. et al., 2022, Nat. Astron., 262 – [6]. Kelley, M. S. & Wooden, D. H., 2009, Planetary and Space Science, 57, 1133, and ref. therein – [7]. Smith, J. D. T., et al., 2007, PASP, 119.1133S – [8]. Markkanen, J. & Agarwal, J., 2020, A&A, 643, A16.

We present high resolution spectra of comet C/2017 K2 (PanSTARRS) (hereafter 17K2), obtained using the upgraded high resolution spectrometer of the VLT, CRIRES+. We will show our findings in the (2.8 – 5.3) μm range, searching for primary volatiles (e.g., H2O, HCN, NH3, CO, C2H6, CH4, ...) and studying their evolution as the comet approach the Sun. 17K2 is a long period comet, very active already at record heliocentric distances of 16 au, and represents a unique opportunity to study the composition of a mostly unaltered comet. Comets formed from the material surrounding the proto-Sun about 4.6 billion years ago, and after their formation they were scattered into their current reservoirs [1,2], where the frozen nuclei have preserved most of the chemical and mineralogical properties linked to their formation site until today. Probing the chemical diversity in comets may thus unveil the processes that were in effect within the mid-plane of our proto-planetary disk, and test the hypothesis that comets may have contributed in delivering water and prebiotics to the early Earth [3]. Among other techniques, the composition of active comets can be studied from ground based telescopes using high resolution spectroscopy in the infrared (IR - 3 to 5 μm), where it is possible to observe emission lines produced by solar-pumped fluorescence of primary species, i.e., molecules released directly from the nucleus. High spectral and spatial resolutions are necessary to resolve different molecular species in the spectra, to study their distribution within the coma and to separate emission lines of the comet from their counterpart in the atmosphere. Comet 17K2 is in excellent observing conditions in 2022, allowing infrared high resolution studies. The comet shows already activity, probably driven by CO and other hyper-volatiles that can sublimate at distances from the Sun larger than 5 au [4,5]. Discovered in 2017 at about 16 au from the Sun [6], it is most likely entering the inner solar system for the first time, and its observation offers a unique opportunity to study its mostly unaltered material. We will present the results obtained from different spectra acquired using CRIRES+ at ESO-VLT at various epochs. We acquired comprehensive high-resolution spectra of the comet as it progressively moved towards the Sun, with the goal of monitoring the evolution of sublimating material with the heliocentric distance. In particular, we have granted time at the beginning of May, beginning of July, and end of August 2022, with the Sun-17K2 distance varying from about 3.5 to 2.3 au. In this heliocentric range, the comet is crossing the CO to H2O ice sublimation regime [7]. Data are reduced using custom semi-automated procedures (see [8] and references therein) that allow a fast analysis of the spectra. Spectral calibration and compensation for telluric absorption are achieved by comparing the data with highly accurate atmospheric radiance and transmittance models obtained with PUMAS/PSG [9]. Flux calibration is obtained using the spectra of a standard star observed closely in time with the comet, and reduced with the same algorithms. Production rates and relative abundances (i.e. mixing ratios with respect to water) of different primary species in the coma are obtained using state-of-the-art fluorescence models (see for example [10] and [11]). The molecular abundances found in this comet will be compared to reference median values retrieved for the comet population [12] and with the abundances found in other Oort Cloud Comets. References: 1. Gomes, R., et al., 2005, Nature, 435, 446 – 2. Morbidelli, A., et al., 2007, AJ, 134, 1790 – 3. Mumma, M. J., Charnley, S.B. 2011, Ann. Rev. Astron. Astroph., 49 – 4. Jewitt, D., et al., 2019, AJ, 157, 65 – 5. Yang, B., et al., 2021, ApJL, 914, L17 – 6. Wainscoat, R. J., et al., 2017, CBET, 4393, 1 – 7. Jewitt, D., et al., 2007, Protostars and Planets V. Univ. Arizona Press, Tucson, 863 – 8. Lippi, M., et al., 2020, AJ, 159, 157 – 9. Villanueva, G. L., et al., 2018, JQSRT, 217, 86 – 10. Villanueva, G. L., et al., 2012b, JQSRT, 113, 202 – 11. Villanueva, G. L., et al., 2011b, JGRE, 116, E08012 – 12. Lippi, M., et al., 2021, AJ, 162, 74.

We will present our observations of the bright comet C/2021 A1 (Leonard) with the newly upgraded CRIRES+ high resolution IR spectrometer mounted on the ESO VLT in Paranal, Chile. C/2021 A1 is a long period comet that reached perihelion on January 3, 2022, at 0.62 AU from the Sun. It is one of the brightest comet of recent years, reaching a visual magnitude of 3 close to perihelion (Seiichi Yoshida's webpage). Originating from the cold Oort Cloud were it spent most of its dynamical lifetime, C/2021 A1 has presumably experienced little transformation or activity, keeping a pristine memory of the chemistry of the protoplanetary disk at the place where it formed. The sublimation of the nucleus volatile ices during its close approach to the Sun was an unique opportunity to have a glimpse at C/2021 A1 composition through the fluorescence of the species in its coma. We observed the comet with CRIRES+ for three nights close to its perihelion at 0.62 AU between December 28, 2021, and January 3, 2022, and derived the production rates of several parent volatiles including H2O, CH4, C2H6, H2CO and CH3OH. During the period of observation, the proximity to the Sun triggered a series of outbursts in C/2021 A1 (Jehin et al, 2022), enhancing the release of material in the coma and ultimately leading to the disintegration of the comet. The observations were made nodding on sky to subtract telluric features in the spectra, and the spectra were later corrected for atmospheric absorption (dominant in the NIR region) and wavelength calibrated by an atmospheric transmittance model computed with the ESO MOLECFIT software (Smette 2015). A flux reference star was also observed to calibrate the target's flux. The chemical composition of the comet will be compared to other comets from the same and other dynamical groups. The ongoing effort to build a chemical taxonomy of comets (A’Hearn et al., 1995; Dello Russo et al., 2016; Lippi et al., 2021) and compare it to the established dynamical classification underlies the need to better constrain the chemical composition of an increasing number individual comets. The high resolution IR spectrometer CRIRES+ is an upgrade of the CRIRES spectrometer into a cross-dispersed spectrograph, increasing the simultaneously covered wavelength by a factor 10 (Dorn et al, 2020). It has been available at the VLT since October 2021, offering a resolving power up to 100000 with a 0.2'' slit between 1 and 5 µm. This first observation of a comet with CRIRES+ will also serve to demonstrate its capabilities to target such objects in the IR.

The long-period comet C/2017 K2 (PanSTARRS) was discovered in 2017 at a large heliocentric distance of 16 au (Wainscoat et al. 2017). Pre-discovery images from 2013 show that K2 was even active at a record distance of ~24 au from the Sun (Jewitt et al. 2017) well beyond the snow line, indicating that, most probably, CO and CO2 ices - the most abundant species after water - might drive its activity. CO was indeed detected in K2’s coma in the sub-mm range at a heliocentric distance of 6.7 au (Yang et al. 2021) and K2 was claimed to be a CO-rich comet. Detecting comets at such large distances is becoming more frequent, but it is still a rare occasion to study a well preserved comet surface coming directly from the Oort Cloud or on a several million years orbit, and especially if it is of a rare type. K2 will reach its perihelion on 2022 December 19 (Rh=1.8 au, Δ=2.5 au) and become a bright target in automn with good observing conditions from the Southern hemisphere. We have started an observing campaign on May 8 (Rh=3.2 au), 2022 with UVES at the ESO VLT to obtain high resolution and good SNR optical spectra to characterize the detailed coma composition of its daughter species before and after K2 perihelion. We report here about the first epochs before perihelion. UVES was setup with a slit width of 0.45" (length of 10") to provide a resolving power of 80.000, and we selected two different settings (DIC#1 346/580 and DIC2 437/860) to cover the whole optical range (304-1040 nm) at each epoch in only two long exposures on the same night. These spectra will allow us to compare K2 - characterized by its unusual distant activity - to other well studied comets in the optical and particularly using the same instrument since 20 years by the Liège comet team. These spectra will allow us to measure the detailed composition of its coma: the production rates of the daughter species (OH, CN, C2 etc.) to check among other things if the comet is a C-chain depleted or normal comet (A'Hearn et al. 1995), to link those production rates with those from the parent species observed in the IR (see CRIRES+ poster by Lippi et al.), to search for CO+ and CO2+ lines to check if K2 is a CO-rich comet like the unique CO-N2-rich blue comet C/2016 R2 (PanSTARRS) (Opitom et al. 2019), to measure the ratio of the [OI] lines to estimate the CO/H2O ratio (Decock et al. 2015), and if the comet is bright enough to measure the isotopic ratios of the light elements (12C/13C and 14N/15N from the CN isotopologues), to measure the ortho- to para- ratio of NH2, and search for faint FeI and NiI lines which are a new and puzzling component of the cometary coma (Manfroid et al. 2021).

Upon its discovery in 2020 March, we requested Director Discretionary Time (DDT) at the NASA/IRTF facility to observe comet C/2020 F3 (NEOWISE), with the high-resolution spectrograph iSHELL. The comet approached the Sun, down to 0.3 au, in early 2020 July, providing a spectacular perihelion passage and revealing itself as one of the brightest comets that have appeared in the northern hemisphere in recent decades. Daytime observations with iSHELL/IRTF were performed to study the comet immediately after its perihelion passage, from 9 July to 1 August. In early August, a DDT at Keck Observatory was requested to continue following the comet with NIRSPEC 2.0. We acquired comprehensive high-resolution spectra of the comet as it progressively retreated from perihelion. We detected many cometary emission lines in the (2.8–5.3) μm range, identifying 12 molecular species: 9 primary volatiles (H2O, HCN, NH3, CO, C2H2, C2H6, CH4, CH3OH, and H2CO) and 3 product species (CN, NH2, OH). In this paper, we present the analysis and discussion of the molecular abundances found in this comet, and we compare them to reference median values for Oort Cloud Comets. Measured molecular mixing ratios showed drastic changes during our observing campaign, which spanned nearly one month from 2020 July 9 to August 6. Here, we provide a detailed discussion of the molecular spatial distributions and their role in identifying the presence of extended sources in the coma. Our investigations provided evidence for the heterogeneous chemical composition of the comet’s nucleus.

The detection of phosphine (PH3) in the atmosphere of Venus has been recently reported based on millimeter-wave radio observations (Greaves et al. 2020), and its re-analyses (Greaves et al. 2021a/b). In this Matters Arising we perform an independent reanalysis, identifying several issues in the interpretation of the spectroscopic data. As a result, we determine sensitive upper-limits for PH3 in Venus' atmosphere (>75 km, above the cloud decks) that are discrepant with the findings in G2020 and G2021a/b. The measurements target the fundamental first rotational transition of PH3 (J=1-0) at 266.944513 GHz, which was observed with the James Clerk Maxwell Telescope (JCMT) in June 2017 and with the Atacama Large Millimeter/submillimeter Array (ALMA) in March 2019. This line's center is near the SO2 (J=309,21-318,24) transition at 266.943329 GHz (only 1.3 km/s away from the PH3 line) which represents a potential source of contamination. The JCMT and ALMA data, as presented in G2020, are at spectral resolutions comparable to the frequency separation of the two lines. Moreover, the spectral features identified are several km/s in width, and therefore do not permit distinct spectroscopic separation of the candidate spectral lines of PH3 and SO2. We present the radiative transfer modelling we have performed and then discuss the ALMA and JCMT analyses in turn.

The goal of this white paper is to provide examples where ground-based and space-based observations are combined, and used to obtain understanding or constrain parameters beyond what the separate measurements could yield.

We present an updated statistical analysis on molecular abundances retrieved from infrared spectra of 20 comets, observed with NIRSPEC-KECK since 1999. Using these results, we investigate the chemical diversity among comets, and we try to correlate them to the chemical and physical processes present during the formation of our planetary system. Introduction: Comets are considered the remnants of the solar system formation. According to recent dynamical models [1], objects that formed between 5 and 17 AU likely scattered into the Oort cloud (OC), the primary source of long period and dynamically-new comets, while those that formed in the outer proto-planetary disk (beyond 17 AU) entered both the Oort cloud and Kuiper belt (KB) reservoirs. Investigating the chemical diversity in comets may unveil the physical and chemical conditions present during the formation and early evolution of our planetary system (e.g. hydrogenation on dust grains in cold environments or photo-dissociation processes due to UV/X-rays/Cosmic-rays radiation), as well as the processes that may have changed the nucleus composition after its formation (e.g. cosmic rays impacting the outer layer of the nucleus or successive surface warming on repeated passages through the inner solar system). Since 1985, more than 60 comets have been investigated using ground based high resolution infrared spectrometers, and many efforts have been made to create a classification of these bodies [2,3]. However, some infrared results published before 2011 may contain systematic inaccuracies related to then-incomplete molecular models used to interpret the fluorescence excitation in comets, to a non-properly described atmospheric transmittance models and/or to the use of immature reduction algorithms. These inaccuracies impact mostly comets that were observed before 2011, and they need to be removed [4]. Here, we present a statistical analysis on our revised data for twenty comets and we investigate their possible connections to processes in the proto-planetary disks and/or the natal cloud. Results and discussion: We have examined the distribution of molecular species among the comet population making use of boxplots (Figure 1). The amount of dispersion that we observe for individual species is expected and could be partially related to the temperature gradient in the proto-planetary disk and/or to the intensity of the radiation field, if present. For instance, the high dispersion range for CO may be related to efficient formation of CH3OH through hydrogenation processes on dust grains at low temperatures (T < 20 K), or formation of CO2 at higher temperatures (T > 20 K) [5]. The differential loss of highly volatile species (e.g. CO and CH4) after the comet formation may also be relevant. In Figure 2, we show two selected scatterplots for some of the analyzed molecules: these trends should reflect, at least in part, the conditions that were present during the formation of comets. We notice for example that CO shows a high and positive correlation with CH4, and a much lower but still positive correlation with CH3OH (an anti-correlation is expected if hydrogenation converted significant CO to CH3OH). Aspects of the interpretation of the scatterplots will be discussed. We compared our results with recent disk models [6,7,8], where the relative amounts of CH3OH, CO, CH4 and C2H6, are expected to depend on what chemical processes and how much radiation field (UV/X/CR) were present at different heliocentric distances from the proto-sun. Considering the combination of these four species (Figure 3), we notice that most of the sampled comets fall in the third and first quadrants and follow an (almost) linear relationship. Depending on the position of the comet with respect to this line, we can define a factor K that can be associated with an increasing processing of the cometary material, and try to reconstruct the chemical and physical history of each analyzed comet. Conclusions: We report an updated statistical analysis on molecular abundances observed in 20 comets and their possible connections with protoplanetary disk models. The results reveal a diversity in comet composition, and different correlations among the observed chemical species, ultimately giving important hints about the physical and chemical condition present during the formation and evolution of our Solar System. Figure 1. Boxplot statistic for the chemical species that we observed in 20 comets; for each box we report the interquartile range (IQR), the median (Med), the skewness (Skw), and the whiskers (error bars of the boxplots). Comets characterized by outlier values are highlighted. Figure 2. Selected scatterplots showing the measured mixing ratios (% with respect to water). For each graphic, the correlation factor is indicated in the upper left corner. Jupiter family and Oort Clouds comets are shown with squares and circles, respectively. Figure 3: Relationship between relative abundances of selected species and possible connections with the formation and evolution of comets in protoplanetary disks. Jupiter family and Oort Clouds comets are shown with squares and circles, respectively. Colors indicate a possible degree of evolution of the cometary material (violet = low degree to red = high degree) due to different processes at different life stages of the comet. This work is supported by the NASA Emerging Worlds Program EW15-57 and the NASA Astrobiology Program 13-13NAI7-0032 References: [1] Morbidelli, A. et al. 2007, Astron. J., 134, 1790; [2] Mumma & Charnley, Ann. Rev A&A, 49, 471 2011; [3] Dello Russo, N. et al. 2016, Icarus, 278, 301; [4] Lippi et al 2020, Astron. J., 159, 157; [5] Tielens, A. G. G. M., Rev. Of Modern Physics, 85, 1021, 2013; [6] Bosman et al. 2018, 618, A182; [7] Walsh 2010 ApJ, 722, 1607; [8] Eistrup et al. 2018, A&A, 613, A14.

We present revised results for the main molecular species in five Oort Cloud comets observed with near-infrared echelle grating spectrometer (NIRSPEC) at the Keck Observatory between 1999 and 2012 (C/1999 S4 (LINEAR), C/2001 A2 (LINEAR), C/2007 W1 (Boattini), C/2012 F6 (Lemmon), and C/2012 S1 (ISON)). The re-evaluation of these data shows the improvement of results in some of the data sets, in particular for comets observed and analyzed before the advent of new and revised fluorescence models and terrestrial retrieval methods introduced since 2011. We observe significant improvements in the resulting rotational temperatures and the production rates for all species, and in mixing ratios of minor species (relative to water). The re-analysis also allowed us to quantify species not analyzed previously, mostly due to the lack of molecular models (e.g., ammonia and formaldehyde). We note, however, that the improvement of these revised values is less substantial for comets observed (and/or analyzed) since 2010.

We observed short-period comet 252P/LINEAR post-perihelion during its 2016 passage, which presented a favorable opportunity to survey its chemical composition at a close Earth approach (∼0.14 au). We characterized the comet’s chemical composition on four dates (UT 2016 April 12, 19, 26, and 29) using spectroscopic measurements with the Near-infrared Spectrograph (NIRSPEC) at the Keck Observatory on Maunakea, HI. Our high-resolution infrared spectra yielded production rates for four species (H2O, CH3OH, C2H6, and HCN) and upper limits for five species (NH3, H2CO, C2H2, CO, and CH4). We measured water at an average production rate of 4.9 ± 0.1 × 10(exp 27) molec s(exp -1). The chemical properties of 252P suggest a rather typical composition, yet somewhat enriched in methanol and ethane but low in formaldehyde (upper limit) compared to other short-period comets surveyed at infrared wavelengths. Analysis of the ortho/para ratio in water indicates a nuclear spin temperature larger than ∼38 K, consistent with statistical equilibrium (2σ). Spatial distributions of gases, which are representative of possible heterogeneity in the nucleus and/or gas dynamics upon sublimation, showed rather symmetric profiles, with subtle enhancements of the more volatile species C2H6 and HCN toward the sunward hemisphere, while water showed spatial distributions that were extended toward the anti-sunward hemisphere. The continuum was characterized by a narrow distribution. We place our infrared results in the context of observations with the Discovery Channel Telescope, the James Clerk Maxwell submillimeter Telescope, and the Hubble Space Telescope.

We report a sensitive search for deuterated water (HDO) in comet 8P/Tuttle using high-resolution spectroscopy at infrared (IR) wavelengths. The deuterium enrichment of cometary water is one of the most important cosmogonic indicators in comets. The ratio preserves information about the conditions under which comet material formed, and tests the possible contribution of comets in delivering water for Earth's oceans. Water (H2O) and HDO were sampled in comet 8P/Tuttle from 2008 January 27 to 2008 February 3 using the new IR spectrometer (Cryogenic Infrared Echelle Spectrograph) at the 8.2 m Antu telescope of the Very Large Telescope Observatory atop Cerro Paranal, Chile. Twenty-three lines of HDO were sampled near 3.7 μm, leading to a production rate of 4.73 ± 1.68 × 1025 s–1. Combining this value with the H2O production rate of 5790 ± 250 × 1025 s–1 provides a formal value of = 4.09 ± 1.45 × 10–4 in comet 8P/Tuttle. This value is larger by a factor of 2.62 ± 0.93 than Vienna Standard Mean Ocean Water, and is comparable to enrichment factors measured for three other Oort cloud comets. The technique described here provides unprecedented sensitivities, ultimately permitting us to routinely measure this prime cosmogonic indicator, even in comets having relatively modest gas production rate like 8P/Tuttle.

Comet C/2006 W3 (Christensen) remained outside a heliocentric distance (Rh) of 3.1 au throughout its apparition, but it presented an exceptional opportunity to directly sense a suite of molecules released from its nucleus. The Cryogenic Infrared Echelle Spectrograph at ESO-VLT detected infrared emissions from the three hypervolatiles (CO, CH4, and C2H6) that have the lowest sublimation temperatures among species that are commonly studied in comets by remote sensing. Even at Rh 3.25 au, the production rate of each molecule exceeded those measured for the same species in a number of other comets, although these comets were observed much closer to the Sun. Detections of CO at Rh = 3.25, 4.03, and 4.73 au constrained its post-perihelion decrease in production rate, which most likely dominated the outgassing. At 3.25 au, our measured abundances scaled as CO/CH4/C2H6 approx. = 100/4.4/2.1. The C2H6/CH4 ratio falls within the range of previously studied comets at Rh < 2 au, while CO/CH4 is comparatively high and similar to in situ measurements from Rosetta at approx.10 km from the nucleus of 67P/Churyumov-Gerasimenko conducted at a very similar Rh (3.15 au). The independent detections of H2O (Herschel Space Observatory) and CO (this work) imply a coma abundance H2O/CO approx. = 20% in C/2006 W3 near Rh = 5 au. All these measurements are of high value for constraining models of nucleus sublimation (plausibly CO-driven) beyond Rh = 3au, where molecular detections in comets are still especially sparse.

We quantified ten parent volatiles in comet C/2009 P1 (Garradd) before perihelion, through high-dispersion infrared spectra acquired with CRIRES at ESO's VLT on UT 2011 August 07 (Rh = 2.4 AU) and September 17-21 (Rh = 2.0 AU). On August 07, water was searched but not detected at an upper limit (3{\sigma}) of 2.1 \times 10^28 s-1, while ethane was detected with a production rate of 6.1 \times 10^26 s-1 (apparent mixing ratio > 2.90%). On September 17-21, the mean production rate for water was 8.4 \times 10^28 s-1, and abundance ratios (relative to water) of detected trace species were: CO (12.51%), CH3OH (3.90%), CH4 (1.24%), C2H6 (1.01%) and HCN (0.36%). Upper limits (3{\sigma}) to abundances for four minor species were: NH3 (1.55%), C2H2 (0.13%), HDO (0.89%) and OCS (0.20%). Given the relatively large heliocentric distance, we explored the effect of water not being fully sublimated within our FOV and identified the 'missing' water fraction needed to reconcile the retrieved abundance ratios with the mean values found for "organics-normal". The individual spatial profiles of parent volatiles and the continuum displayed rather asymmetric outgassing. Indications of H2O and CO gas being released in different directions suggest different active vents and/or the possible existence of polar and apolar ice aggregates in the nucleus. The high fractional abundance of CO identifies comet C/2009 P1 as a CO-rich comet., Comment: To appear in: The Astrophysical Journal Letters (LET27048R)

We report measurements of eight primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, C2H2, H2CO, and NH3) and two product species (OH and NH2) in comet 103P/Hartley-2 using high dispersion infrared spectroscopy. We quantified the long- and short-term behavior of volatile release over a three-month interval that encompassed the comet's close approach to Earth, its perihelion passage, and flyby of the comet by the Deep Impact spacecraft during the EPOXI mission. We present production rates for individual species, their mixing ratios relative to water, and their spatial distributions in the coma on multiple dates. The production rates for water, ethane, HCN, and methanol vary in a manner consistent with independent measures of nucleus rotation, but mixing ratios for HCN, C2H6, & CH3OH are independent of rotational phase. Our results demonstrate that the ensemble average composition of gas released from the nucleus is well defined, and relatively constant over the three-month interval (September 18 through December 17). If individual vents vary in composition, enough diverse vents must be active simultaneously to approximate (in sum) the bulk composition of the nucleus. The released primary volatiles exhibit diverse spatial properties which favor the presence of separate polar and apolar ice phases in the nucleus, establish dust and gas release from icy clumps (and also, directly from the nucleus), and provide insights into the driver for the cyanogen (CN) polar jet. The spatial distributions of C2H6 & HCN along the near-polar jet (UT 19.5 October) and nearly orthogonal to it (UT 22.5 October) are discussed relative to the origin of CN. The ortho-para ratio (OPR) of water was 2.85 \pm 0.20; the lower bound (2.65) defines Tspin > 32 K. These values are consistent with results returned from ISO in 1997., 18 pages, 3 figures, to be published in: Astrophysical Journal Letters

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ∼16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. Fil: Meech, K. J.. Institute for Astronomy; Estados Unidos Fil: A’Hearn, M. F.. University of Maryland; Estados Unidos Fil: Adams, J. A.. Cornell University; Estados Unidos Fil: Bacci, P.. Centro Astronomico di Libbiano; Italia Fil: Bai, J.. Chinese Academy of Sciences; China Fil: Barrera, L.. Universidad Metropolitana de Ciencias de la Educacion; Chile Fil: Battelino, M.. Swedish Space Corporation; Suecia Fil: Bauer, J. M.. Jet Propulsion Laboratory; Estados Unidos Fil: Becklin, E.. Stratospheric Observatory for Infrared Astronomy; Estados Unidos Fil: Bhatt, B.. Indian Institute of Astrophysics; India Fil: Biver, N.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Bockelee Morvan, D.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Bodewits, D.. University of Maryland; Estados Unidos Fil: Bohnhardt, H.. Gobierno de la Republica Federal de Alemania. Max Planck Institut Fur Astrophysik; Alemania Fil: Boissier, J.. Inst. di Radioastronomia; Italia Fil: Bonev, B. P.. Catholic University of America; Estados Unidos Fil: Borghini, W.. Osservatorio Astronomico Naturalistico di Casasco; Italia Fil: Brucato, J. R.. Osservatorio Astrofisico di Arcetri; Italia Fil: Bryssinck, E.. Brixiis Observatory; Bélgica Fil: Buie. M. W.. Southwest Research Institute; Estados Unidos Fil: Canovas, H.. Utrecht University; Países Bajos Fil: Castellano, D.. Unione Astrofili Italiani; Italia Fil: Charnley, S. B.. National Aeronautics And Space Administration; Estados Unidos Fil: Chen, W. P.. National Taiwan Normal University; Corea del Sur Fil: Chiang, P.. Korea Astronomy and Space Science Institute; Corea del Sur Fil: Choi, Y. J.. Korea Astronomy and Space Science Institute; Corea del Sur Fil: Christian, D. J.. California State University; Estados Unidos Fil: Chuang, Y. L.. National Taiwan Normal University; Corea del Sur Fil: Cochran, A. L.. University of Texas; Estados Unidos Fil: Melita, Mario Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

We measured organic volatiles (CH4, CH3OH, C2H6, H2CO), CO, and water in comet 8P/Tuttle, a comet from the Oort cloud reservoir now in a short-period Halley-type orbit. We compare its composition with two other comets in Halley-type orbits, and with comets of the "organics-normal" and "organics-depleted" classes. Chemical gradients are expected in the comet-forming region of the proto-planetary disk, and an individual comet should reflect its specific heritage. If Halley-type comets came from the inner Oort cloud as proposed, we see no common characteristics that could distinguish such comets from those that were stored in the outer Oort cloud., 14 pages, including 1 figure and 2 Tables

Aims. Hydrogen cyanide (HCN) radiates effectively at infrared wavelengths in cometary atmospheres, and a new quantum-band model is needed to properly interpret high-resolution spectra. HCN spectra of comets 8P/Tuttle, C/2007 W1 (Boattini), and C/2008 Q3 (Garradd) have been recorded by our team using the high-resolution CRyogenic InfraRed Echelle Spectometer (CRIRES) at the Very Large Telescope (VLT), ultimately posing an excellent test for our newly developed model. Methods. We developed a quantum-band model for the ν1 fundamental of HCN using the latest spectroscopic parameters available and with it retrieved HCN in the above mentioned three comets. For each comet, we sampled several lines of HCN in the spectral region near 3 μm, and retrieved molecular production rates, mixing ratios, and rotational temperatures. Results. When compared to other comets, 8P/Tuttle is relatively depleted in HCN, while C/2007 W1 (Boattini) appears to be enriched and C/2008 Q3 (Garradd) normal. The spatial profile of HCN observed in 8P/Tuttle is symmetric, consistent with isotropic outgassing from the nucleus, while in comet C/2007 W1 we observed an asymmetric excess of HCN in the anti-solar direction. We investigated the HCN-CN parentage by comparing our production rate ratios (HCN/H2O) with those of CN/OH derived at optical wavelengths. In comet C/2007 W1 the two mixing ratios are comparable, while in 8P/Tuttle our derived HCN abundance is too low to support the HCN molecule as the only parent of the CN radical.