J. Crovisier

Paris Diderot University, Lutetia Parisorum, Île-de-France, France

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Publications (562)1399.89 Total impact

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    ABSTRACT: The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets represent some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C2H5OH) and the simplest monosaccharide sugar glycolaldehyde (CH2OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar- type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.
    Science Advances 10/2015; 1(9):e1500863-e1500863. DOI:10.1126/sciadv.1500863
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    ABSTRACT: The high obliquity (~50°) of comet 67P/Churyumov-Gerasimenko (67P) is responsible for a long-lasting winter polar night in the southern regions of the nucleus. We report observations made with the submillimeter and millimeter continuum channels of the Microwave Instrument onboard the Rosetta Orbiter (MIRO) of the thermal emission from these regions during the period August-October 2014. Before these observations, the southern polar regions had been in darkness for approximately five years. Subsurface temperatures in the range 25-50 K are measured. Thermal model calculations of the nucleus near-surface temperatures carried out over the orbit of 67P, coupled with radiative transfer calculations of the MIRO channels brightness temperatures, suggest that these regions have a thermal inertia within the range 10-60 J m-2 K-1 s-0.5. Such low thermal inertia values are consistent with a highly porous, loose, regolith-like surface. These values are similar to those derived elsewhere on the nucleus. A large difference in the brightness temperatures measured by the two MIRO continuum channels is tentatively attributed to dielectric properties that differ significantly from the sunlit side, within the first few tens of centimeters. This is suggestive of the presence of ice(s) within the MIRO depths of investigation in the southern polar regions. These regions started to receive sunlight in May of 2015, and refinements of the shape model in these regions, as well as continuing MIRO observations of 67P, will allow refining these results and reveal the thermal properties and potential ice content of the southern regions in more detail.
    Astronomy and Astrophysics 09/2015; 583. DOI:10.1051/0004-6361/201526181 · 4.38 Impact Factor
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    ABSTRACT: We present the spatial and diurnal variation of water outgassing on comet 67P/Churyumov-Gerasimenko using the HO rotational transition line at 556.936 GHz observed from Rosetta/MIRO in August 2014. Methods. The water line was analyzed with a non-LTE radiative transfer model and an optimal estimation method to retrieve the H162O outgassing intensity, expansion velocity, and gas kinetic temperature. On August 7-9, 2014 and August 18-19, 2014, MIRO performed long steady nadir-pointing observations of the nucleus while it was rotating around its spin axis. The ground track of the MIRO beam during the observation was mostly on the northern hemisphere of comet 67P, covering its three distinct parts: the so-called head, body, and neck areas. Results. The MIRO spectral observation data show that the water-outgassing intensity varies by a factor of 30, from 0.1 × 1025 molecules s-1 sr-1 to 3.0 × 1025 molecules s-1 sr-1, the terminal gas expansion velocity varies by 0.17 km s-1 from 0.61 km s-1 to 0.78 km s-1, and the terminal gas temperature varies by 27 K from 47 K to 74 K. The retrieved coma parameters are co-registered with local environment variables such as the subsurface temperatures, measured in the MIRO continuum bands, the local solar time, illumination condition, and beam location on nucleus. The spatial variation of the outgassing activity is very noticeable, and the largest outgassing activity in August 2014 occurs near the neck region of the nucleus. The outgassing activity in the neck region is also found to be correlated with the local solar hour, which is related to the local illumination condition.
    Astronomy and Astrophysics 09/2015; 583. DOI:10.1051/0004-6361/201526155 · 4.38 Impact Factor
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    ABSTRACT: Observations of the nucleus of 67P/Churyumov-Gerasimenko in the millimeter-wave continuum have been obtained by the Microwave Instrument for the Rosetta Orbiter (MIRO). We present data obtained at wavelengths of 0.5 mm and 1.6 mm during September 2014 when the nucleus was at heliocentric distances between 3.45 and 3.27 AU. The data are fit to simple models of the nucleus thermal emission in order to characterize the observed behavior and make quantitative estimates of important physical parameters, including thermal inertia and absorption properties at the MIRO wavelengths. MIRO brightness temperatures on the irregular surface of 67P are strongly affected by the local solar illumination conditions, and there is a strong latitudinal dependence of the mean brightness temperature as a result of the seasonal orientation of the comet's rotation axis with respect to the Sun. The MIRO emission exhibits strong diurnal variations, which indicate that it arises from within the thermally varying layer in the upper centimeters of the surface. The data are quantitatively consistent with very low thermal inertia values, between 10-30 J K-1 m-2 s-1/2, with the 0.5 mm emission arising from 1 cm beneath the surface and the 1.6 mm emission from a depth of 4 cm. Although the data are generally consistent with simple, homogeneous models, it is difficult to match all of its features, suggesting that there may be some vertical structure within the upper few centimeters of the surface. The MIRO brightness temperatures at high northern latitudes are consistent with sublimation of ice playing an important role in setting the temperatures of these regions where, based on observations of gas and dust production, ice is known to be sublimating.
    Astronomy and Astrophysics 09/2015; 583. DOI:10.1051/0004-6361/201526152 · 4.38 Impact Factor
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    ABSTRACT: Context. Outgassing from cometary nuclei involves complex surface and subsurface processes that need to be understood to investigate the composition of cometary ices from coma observations. Aims. We investigate the production of water, carbon dioxide, and carbon monoxide from the nucleus of comet 67P/ChuryumovGerasimenko (67P). These species have different volatility and are key species of cometary ices. Methods. Using the high spectral-resolution channel of the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-H), we observed the ν3 vibrational bands of H2O and CO2 at 2.67 and 4.27 µm, respectively, from 24 November 2014 to 24 January 2015, when comet 67P was between 2.91 and 2.47 AU from the Sun. Observations were undertaken in limb-viewing geometry at distances from the surface of 0 to 1.5 km and with various line-of-sight (LOS) orientations in the body-fixed frame. A geometry tool was used to characterize the position of the LOS with respect to geomorphologic regions and the illumination properties of these regions. Results. The water production of 67P did not increase much from 2.9 to 2.5 AU. High water column densities are observed for LOS above the neck regions, suggesting they are the most productive in water vapor. While water production is weak in regions with low solar illumination, CO2 is outgassing from both illuminated and non-illuminated regions, which indicates that CO2 sublimates at a depth that is below the diurnal skin depth. The CO2/H2O column density ratio varies from 2 to 60%. For regions that are in sunlight, mean values between 2 and 7% are measured. The lower bound value is likely representative of the CO2/H2O production rate ratio from the neck regions. For carbon monoxide, we derive column density ratios CO/H2O < 1.9% and CO/CO2 < 80%. An illumination-driven model, with a uniformly active surface releasing water at a mean rate of 8 × 1025 s−1, provides an overall agreement to VIRTIS-H data, although some mismatches show local surface inhomogeneities in water production. Rotational temperatures of 90–100 K are derived from H2O and CO2 averaged spectra.
    Astronomy and Astrophysics 09/2015; 583. DOI:10.1051/0004-6361/201526303 · 4.38 Impact Factor
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    ABSTRACT: Comets are uniquely pristine bodies providing unique insights about the formation of our Solar System. In this work, we focus on a dynamically new comet as it enters the inner Solar System for the first time after residing for billion of years in the Oort Cloud. Such comets are particularly important because they are thought to be not differentiated by solar radiation and they are supposed to have a large quantity of organic matter close to the surface. Here we report the results of a search for NH3(1,1) emission at 23.7 GHz towards comet C/2012 S1 (ISON) using a new dual-feed K band receiver mounted on the Medicina 32-m antenna. We observed the comet close to its perihelion, from 25 to 29 November 2013, when its heliocentric distance changed from 0.25 AU to 0.03 AU. We derive an upper limit of Q(NH3) of about 2.5×1029 mol s−1 on 26 November, that is consistent with the last peak of water production rate of ∼2×1030 mol s−1 within the last few days before the perihelion.
    Planetary and Space Science 06/2015; DOI:10.1016/j.pss.2015.06.009 · 1.88 Impact Factor
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    ABSTRACT: Introduction: Taking advantage of Rosetta's ter-minator orbits around 67P/CG nucleus in December 2014, VIRTIS-M, the mapping channel of the Visible and Infrared Thermal Imaging Spectrometer [1] has carried out systematic observations of the comet limb in the 0.25-5 µm spectral range with the aim to detect fluorescence emissions of gas species like water vapour and carbon dioxide [2]. We report about the first detections of these molecules by VIRTIS-M and correlate them with respect to the nucleus orientation at the time of the observation. These features appear variable in time, depending on numerous parameters like com-et's activity state, relative position of the spacecraft with respect to the nucleus, tangent altitude of the line of sight above the limb, heliocentric distance and solar phase. Water vapour emission at 2.7 µm appears considerably more intense in correspondence of the jets emitted by the active regions in the neck while carbon dioxide emission at 4.25 µm increases in limb observations taken above the head and body regions. Coma observations: In December 2014 VIRTIS has performed an extensive campaign dedicated to 67P/CG coma characterization. These observations consist of repeated limb scans taken on the coma above the illuminated part of the nucleus. From a typical spacecraft altitude above the comet's nucleus of 20 km VIRTIS-M is able to acquire the innermost part of the coma, from the surface up to altitude of about 400-500 m with spatial resolution of about 5 m/pixel. Moreover the 3.7° wide VIRTIS-M field of view allows to image a large region of the sun illuminated coma above the nucleus where the maximum fluorescence emissions of the gasesous species occur. Starting from October 2014, VIRTIS-H channel has detected similar emissions on high-resolution (λ/ Δλ=1300-3000) point spectra in the 2-5 µm range [3]. In the following we describe the first detection of water vapour and carbon dioxide fluorescence emissions detected by VIRTIS-M in two coma observation campaigns carried out in de-cember 2014: 1) session MTP010-STP033, acquired on 2014-12-14 from a spacecraft-comet distance of about 20 km, solar phase of about 91° and spacecraft offnadir angle of 5.4°; 2) session MTP010-STP034 executed on 2014-12-17 from a distance of about 20 km, solar phase 92.7° and spacecraft offnadir angle of 7.1°. The relative position of VIRTIS-M slit and field of view (FOV) at the time of these observations is shown in Fig. 1. On the first half of STP033 sequence VIRTIS has observed the coma above the night hemisphere of the head region (observations I1_00377200411 and I1_00377202271) while on the second half it was pointing above the neck active region (observations I1_00377208511 and I1_00377210370). In MTP010/STP034 VIRTIS-M FOV was spanning across the coma region extending above the neck active area for all the time. At the time of these observations the comet's heliocentric distance was 2.77 AU.
    46th Lunar and Planetary Science Conference, The Woodlands, Texas; 03/2015
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    ABSTRACT: Comparison of their chemical compositions shows, to first order, a good agreement between the cometary and interstellar abundances. However, a complex O-bearing organic molecule, ethylene glycol (CH$_{2}$OH)$_{2}$, seems to depart from this correlation because it was not easily detected in the interstellar medium although it proved to be rather abundant with respect to other O-bearing species in comet Hale-Bopp. Ethylene glycol thus appears, together with the related molecules glycolaldehyde CH$_{2}$OHCHO and ethanol CH$_{3}$CH$_{2}$OH, as a key species in the comparison of interstellar and cometary ices as well as in any discussion on the formation of cometary matter. We focus here on the analysis of ethylene glycol in the nearest and best studied hot core-like region, Orion-KL. We use ALMA interferometric data because high spatial resolution observations allow us to reduce the line confusion problem with respect to single-dish observations since different molecules are expected to exhibit different spatial distributions. Furthermore, a large spectral bandwidth is needed because many individual transitions are required to securely detect large organic molecules. Confusion and continuum subtraction are major issues and have been handled with care. We have detected the aGg' conformer of ethylene glycol in Orion-KL. The emission is compact and peaks towards the Hot Core close to the main continuum peak, about 2" to the south-west; this distribution is notably different from other O-bearing species. Assuming optically thin lines and local thermodynamic equilibrium, we derive a rotational temperature of 145 K and a column density of 4.6 10$^{15}$ cm$^{-2}$. The limit on the column density of the gGg' conformer is five times lower.
    Astronomy and Astrophysics 02/2015; 576. DOI:10.1051/0004-6361/201424588 · 4.38 Impact Factor
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    ABSTRACT: Heat transport and ice sublimation in comets are interrelated processes reflecting properties acquired at the time of formation and during subsequent evolution. The Microwave Instrument on the Rosetta Orbiter (MIRO) acquired maps of the subsurface temperature of comet 67P/Churyumov-Gerasimenko, at 1.6 mm and 0.5 mm wavelengths, and spectra of water vapor. The total H2O production rate varied from 0.3 kg s(-1) in early June 2014 to 1.2 kg s(-1) in late August and showed periodic variations related to nucleus rotation and shape. Water outgassing was localized to the "neck" region of the comet. Subsurface temperatures showed seasonal and diurnal variations, which indicated that the submillimeter radiation originated at depths comparable to the diurnal thermal skin depth. A low thermal inertia (~10 to 50 J K(-1) m(-2) s(-0.5)), consistent with a thermally insulating powdered surface, is inferred. Copyright © 2015, American Association for the Advancement of Science.
    Science 01/2015; 347(6220):aaa0709. DOI:10.1126/science.aaa0709 · 33.61 Impact Factor
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    ABSTRACT: The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared ranges (5 to 25 and 1.5 to 5% kÅ(-1)), and the broad absorption feature in the 2.9-to-3.6-micrometer range present across the entire illuminated surface are compatible with opaque minerals associated with nonvolatile organic macromolecular materials: a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups. In active areas, the changes in spectral slope and absorption feature width may suggest small amounts of water-ice. However, no ice-rich patches are observed, indicating a generally dehydrated nature for the surface currently illuminated by the Sun. Copyright © 2015, American Association for the Advancement of Science.
    Science 01/2015; 347(6220):aaa0628. DOI:10.1126/science.aaa0628 · 33.61 Impact Factor
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    ABSTRACT: Volatile abundances in Jupiter-family Comet 81P/Wild 2 were measured on four dates in February and March 2010 using high-dispersion (λΔλ ∼ 2.5 × 104) infrared spectroscopy with NIRSPEC at the W.M. Keck Observatory. H2O was detected on all dates, including measurements on UT March 29 of lines from the ν2 + ν3 − ν2 hot-band not previously targeted in comets. C2H6 and HCN were detected on three dates, and CH3OH was detected on one date. Tentative detections or upper-limits are reported for CH3OH on other dates, as well as for C2H2, H2CO, and NH3. Abundances of all species relative to H2O are in the typical range with the exception of CH3OH, which is depleted compared to other comets. Gas production was significantly higher in late February than in late March. Rotational temperatures were determined for H2O on UT February 22 and 23 and found to be about 30–40 K. The spatial distributions of H2O, C2H6, and CH3OH are all symmetric and similar to the spatial distribution of the dust continuum. H2O abundances from this work are compared to other measurements from both the 1997 and 2010 apparitions. There is no clear evidence of a change in overall gas productivity between the two apparitions within measurement accuracy. Abundances of C2H2, C2H6, HCN and NH3 are consistent with these species being the primary parents of C2, CN, NH and NH2 as measured at optical wavelengths. Although optically classified as carbon-chain depleted, Wild 2 appears more chemically similar in parent volatile chemistry to carbon-chain typical comets; however, we note that in the small sample of Jupiter-family comets measured to date, each comet is chemically distinct.
    Icarus 08/2014; 238:125–136. DOI:10.1016/j.icarus.2014.05.021 · 3.04 Impact Factor
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    ABSTRACT: This paper reviews the recent findings of the Herschel Solar System Observations Key Program (Hartogh et al. 2009b), as well as ground-based supporting observations, regarding the origin of external oxygen in the environments of Jupiter and Saturn. Herschel-HIFI and PACS observations have been used to shown that the Shoemaker-Levy 9 comet is the source of Jupiter's stratospheric water, and that Enceladus (and its geysers) are most probably the source of water for Saturn and Titan.
    Journées 2014 de la Société Française d’Astronomie & d’Astrophysique (SF2A), Paris; 06/2014
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    ABSTRACT: We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R 25,000) at the Keck II Telescope on UT 2012 January 9 and 10, about a week after an outburst had occurred. Over the two nights of our observations, prominent emission lines of CH4 and C2H6, along with weaker emission lines of H2O, HCN, CH3OH, and CO were detected. The gas production rate of CO was comparable to that of H2O during the outburst. The mixing ratios of CO, HCN, CH4, C2H6, and CH3OH with respect to H2O were higher than those for normal comets by a factor of five or more. The enrichment of CO and CH4 in comet Hill suggests that the sublimation of these hypervolatiles sustained the outburst of the comet. Some fraction of water in the inner coma might exist as icy grains that were likely ejected from nucleus by the sublimation of hypervolatiles. Mixing ratios of volatiles in comet Hill are indicative of the interstellar heritage without significant alteration in the solar nebula.
    The Astrophysical Journal 05/2014; 788(2):110. DOI:10.1088/0004-637X/788/2/110 · 5.99 Impact Factor
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    ABSTRACT: A spectral survey in the 1 mm wavelength range was undertaken in the long-period comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) using the 30 m telescope of the Institut de radioastronomie millim\'etrique (IRAM) in April and November-December 2013. We report the detection of ethylene glycol (CH$_2$OH)$_2$ (aGg' conformer) and formamide (NH$_2$CHO) in the two comets. The abundances relative to water of ethylene glycol and formamide are 0.2-0.3% and 0.02% in the two comets, similar to the values measured in comet C/1995 O1 (Hale-Bopp). We also report the detection of HCOOH and CH$_3$CHO in comet C/2013 R1 (Lovejoy), and a search for other complex species (methyl formate, glycolaldehyde).
    Astronomy and Astrophysics 05/2014; 566. DOI:10.1051/0004-6361/201423890 · 4.38 Impact Factor
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    ABSTRACT: We aimed to measure the H2O and dust production rates in C/2006 W3 (Christensen) with the Herschel Space Observatory at a heliocentric distance of ~ 5 AU. We have searched for emission in the H2O and NH3 ground-state rotational transitions at 557 GHz and 572 GHz, simultaneously, with HIFI onboard Herschel on UT 1.5 September 2010. Photometric observations of the dust coma in the 70 and 160 {\mu}m channels were acquired with the PACS instrument on UT 26.5 August 2010. A tentative 4-{\sigma} H2O line emission feature was found in the spectra obtained with the HIFI wide-band and high-resolution spectrometers, from which we derive a water production rate of $2.0(5) \times 10^{27}$ molec. s$^{-1}$. A 3-{\sigma} upper limit for the ammonia production rate of <$1.5 \times 10^{27}$ molec. s$^{-1}$ is obtained taking into account the contribution from all hyperfine components. The blueshift of the water line detected by HIFI suggests preferential emission from the subsolar point. However, it is also possible that water sublimation occurs in small ice-bearing grains that are emitted from an active region on the nucleus surface at a speed of ~ 0.2 km s$^{-1}$. The dust thermal emission was detected in the 70 and 160 {\mu}m filters, with a more extended emission in the blue channel. The dust production rates, obtained for a dust size distribution index that explains the fluxes at the photocenters of the PACS images, lie in the range 70-110 kg s$^{-1}$. Scaling the CO production rate measured post-perihelion at 3.20 and 3.32 AU, these values correspond to a dust-to-gas production rate ratio in the range 0.3-0.4. The dust production rates derived in August 2010 are roughly one order of magnitude lower than in September 2009, suggesting that the dust-to-gas production rate ratio remained approximately constant during the period when the activity became increasingly dominated by CO outgassing.
    Astronomy and Astrophysics 04/2014; 564. DOI:10.1051/0004-6361/201423427 · 4.38 Impact Factor
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    ABSTRACT: The 'snowline' conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Models suggest that some of the icy bodies may have migrated into the asteroid belt. Recent observations indicate the presence of water ice on the surface of some asteroids, with sublimation a potential reason for the dust activity observed on others. Hydrated minerals have been found on the surface of the largest object in the asteroid belt, the dwarf planet (1) Ceres, which is thought to be differentiated into a silicate core with an icy mantle. The presence of water vapour around Ceres was suggested by a marginal detection of the photodissociation product of water, hydroxyl (ref. 12), but could not be confirmed by later, more sensitive observations. Here we report the detection of water vapour around Ceres, with at least 10(26) molecules being produced per second, originating from localized sources that seem to be linked to mid-latitude regions on the surface. The water evaporation could be due to comet-like sublimation or to cryo-volcanism, in which volcanoes erupt volatiles such as water instead of molten rocks.
    Nature 01/2014; 505(7484):525-7. DOI:10.1038/nature12918 · 41.46 Impact Factor
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    ABSTRACT: HCl and HF are expected to be the main reservoirs of fluorine and chlorine wherever hydrogen is predominantly molecular. They are found to be strongly depleted in dense molecular clouds, suggesting freeze-out onto grains in such cold environments. We can then expect that HCl and HF were also the major carriers of Cl and F in the gas and icy phases of the outer solar nebula, and were incorporated into comets. We aimed to measure the HCl and HF abundances in cometary ices as they can provide insights on the halogen chemistry in the early solar nebula. We searched for the J(1-0) lines of HCl and HF at 626 and 1232 GHz, respectively, using the HIFI instrument on board the Herschel Space Observatory. HCl was searched for in comets 103P/Hartley 2 and C/2009 P1 (Garradd), whereas observations of HF were conducted in comet C/2009 P1. In addition, observations of H$_2$O and H$_2^{18}$O lines were performed in C/2009 P1 to measure the H$_2$O production rate. Three lines of CH$_3$OH were serendipitously observed in the HCl receiver setting. HCl is not detected, whereas a marginal (3.6-$\sigma$) detection of HF is obtained. The upper limits for the HCl abundance relative to water are 0.011% and 0.022%, for 103P and C/2009 P1, respectively, showing that HCl is depleted with respect to the solar Cl/O abundance by a factor more than 6$^{+6}_{-3}$ in 103P, where the error is related to the uncertainty in the chlorine solar abundance. The marginal HF detection obtained in C/2009 P1 corresponds to an HF abundance relative to water of (1.8$\pm$0.5) $\times$ 10$^{-4}$, which is approximately consistent with a solar photospheric F/O abundance. The observed depletion of HCl suggests that HCl was not the main reservoir of chlorine in the regions of the solar nebula where these comets formed. HF was possibly the main fluorine compound in the gas phase of the outer solar nebula.
    Astronomy and Astrophysics 01/2014; 562. DOI:10.1051/0004-6361/201322939 · 4.38 Impact Factor

Publication Stats

7k Citations
1,399.89 Total Impact Points


  • 2011-2015
    • Paris Diderot University
      Lutetia Parisorum, Île-de-France, France
    • Max Planck Institute for Solar System Research
      Göttingen, Lower Saxony, Germany
  • 1970-2011
    • Observatoire de Paris
      Lutetia Parisorum, Île-de-France, France
  • 2010
    • Durham University
      Durham, England, United Kingdom
  • 2009-2010
    • Laboratoire d'Etudes en Géophysique et Óceanographie Spatiales
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2003-2007
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
    • Institut de Radioastronomie Millimétrique
      Grenoble, Rhône-Alpes, France
  • 2001-2007
    • Johns Hopkins University
      • Applied Physics Laboratory
      Baltimore, Maryland, United States
    • European Space Agency
      Lutetia Parisorum, Île-de-France, France
  • 1999
    • The Ecological Society of America
      ISO, North Carolina, United States
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands
  • 1998
    • Pennsylvania State University
      University Park, Maryland, United States
    • University of Oxford
      • Atmospheric, Oceanic and Planetary Physics Research Group
      Oxford, England, United Kingdom
  • 1981-1996
    • University of Massachusetts Amherst
      • Department of Astronomy
      Amherst Center, Massachusetts, United States
  • 1995
    • California Institute of Technology
      • Jet Propulsion Laboratory
      Pasadena, California, United States
  • 1986
    • University of Granada
      Granata, Andalusia, Spain
  • 1985
    • University of Minnesota Duluth
      Duluth, Minnesota, United States
  • 1981-1985
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States