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1. Oxygen-bearing organic molecules in comet 67P's dusty coma: first evidence for abundant heterocycles

Author

Hänni, N., Altwegg, K., Baklouti, D., Combi, M., Fuselier, S. A., De Keyser, J., Müller, D. R., Rubin, M., and Wampfler, S. F.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The puzzling complexity of terrestrial biomolecules is driving the search for complex organic molecules in the Interstellar Medium (ISM) and serves as a motivation for many in situ studies of reservoirs of extraterrestrial organics from meteorites and interplanetary dust particles (IDPs) to comets and asteroids. Comet 67P/Churyumov-Gerasimenko (67P) -- the best-studied comet to date -- has been visited and accompanied for two years by the European Space Agency's Rosetta spacecraft. Around 67P's perihelion and under dusty conditions, the high-resolution mass spectrometer on board provided a spectacular glimpse into this comet's chemical complexity. For this work, we analyzed in unprecedented detail the O-bearing organic volatiles. In a comparison of 67P's inventory to molecules detected in the ISM, in other comets, and in Soluble Organic Matter (SOM) extracted from the Murchison meteorite, we also highlight the (pre)biotic relevance of different chemical groups of species. We report first evidence for abundant extraterrestrial O-bearing heterocycles (with abundances relative to methanol often on the order of 10% with a relative error margin of 30-50%) and various representatives of other molecule classes such as carboxylic acids and esters, aldehydes, ketones, and alcohols. Like with the pure hydrocarbons, some hydrogenated forms seem to be dominant over their dehydrogenated counterparts. An interesting example is tetrahydrofuran (THF) as it might be a more promising candidate for searches in the ISM than the long-sought furan itself. Our findings not only support and guide future efforts to investigate the origins of chemical complexity in space, but also they strongly encourage studies of, e.g., the ratios of unbranched vs. branched and hydrogenated vs. dehydrogenated species in astrophysical ice analogs in the laboratory as well as by modeling., Comment: Reproduced with permission from Astronomy & Astrophysics, copyright ESO

Published
2023
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2. Abundant ammonium hydrosulphide embedded in cometary dust grains

Author

Altwegg, K., Combi, M., Fuselier, S. A., Hänni, N., De Keyser, J., Mahjoub, A., Müller, D. R., Pestoni, B., Rubin, M., and Wampfler, S. F.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Ammonium hydrosulphide has long since been postulated to exist at least in certain layers of the giant planets. Its radiation products may be the reason for the red colour seen on Jupiter. Several ammonium salts, the products of NH3 and an acid, have previously been detected at comet 67P/Churyumov-Gerasimenko. The acid H2S is the fifth most abundant molecule in the coma of 67P followed by NH3. In order to look for the salt NH4+SH-, we analysed in situ measurements from the Rosetta/ROSINA Double Focusing Mass Spectrometer during the Rosetta mission. NH3 and H2S appear to be independent of each other when sublimating directly from the nucleus. However, we observe a strong correlation between the two species during dust impacts, clearly pointing to the salt. We find that NH4+SH- is by far the most abundant salt, more abundant in the dust impacts than even water. We also find all previously detected ammonium salts and for the first time ammonium fluoride. The amount of ammonia and acids balance each other, confirming that ammonia is mostly in the form of salt embedded into dust grains. Allotropes S2 and S3 are strongly enhanced in the impacts, while H2S2 and its fragment HS2 are not detected, which is most probably the result of radiolysis of NH4+SH-. This makes a prestellar origin of the salt likely. Our findings may explain the apparent depletion of nitrogen in comets and maybe help to solve the riddle of the missing sulphur in star forming regions., Comment: accepted by MNRAS

Published
2022
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6. Cyanogen, cyanoacetylene, and acetonitrile in comet 67P and their relationship to the cyano radical

Author

Hänni, N., Altwegg, K., Balsiger, H., Combi, M., Fuselier, S. A., De Keyser, J., Pestoni, B., Rubin, M., and Wampfler, S. F.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The cyano radical (CN) is one of the most frequently remotely observed species in space, also in comets. Data from the high-resolution Double Focusing Mass Spectrometer (DFMS) on board the Rosetta orbiter, collected in the inner coma of comet 67P/Churyumov-Gerasimenko, revealed an unexpected chemical complexity, and, recently, also more CN than expected from photodissociation of its most likely parent hydrogen cyanide (HCN). This work is dedicated to the derivation of abundances relative to HCN of three cometary nitriles (including structural isomers) from DFMS data. Mass spectrometry of complex mixtures does not always allow distinction of structural isomers. We assumed the most stable and most abundant (in similar environments) structure in our analysis, that is HCN for CHN, CH3CN for C2H3N, HC3N for C3HN, and NCCN for C2N2. For cyanoacetylene (HC3N) and acetonitrile (CH3CN) the complete mission timeline was evaluated, while cyanogen (NCCN) often was below detection limit. By carefully selecting periods where cyanogen was above detection limit, we were able to follow the abundance ratio between NCCN and HCN from 3.16 au inbound to 3.42 au outbound. These are the first measurements of NCCN in a comet.We find that neither NCCN, nor any of the other two nitriles, is sufficiently abundant to be a relevant alternative parent to CN.

Published
2021
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7. Molecule dependent oxygen isotopic ratios in the coma of comet 67P/Churyumov-Gerasimenko

Author

Altwegg, K., Balsiger, H., Combi, M., De Keyser, J., Drozdovskaya, M. N., Fuselier, S. A., Gombosi, T. I., Hänni, N., Rubin, M., Schuhmann, M., Schroeder, I., and Wampfler, S.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The ratios of the three stable oxygen isotopes 16O, 17O and 18O on Earth and, as far as we know in the solar system, show variations on the order of a few percent at most, with a few outliers in meteorites. However, in the interstellar medium there are some highly fractionated oxygen isotopic ratios in some specific molecules. The goal of this work is to investigate the oxygen isotopic ratios in different volatile molecules found in the coma of comet 67P/Churyumov-Gerasimenko and compare them with findings from interstellar clouds in order to assess commonalities and differences. To accomplish this goal, we analyzed data from the ROSINA instrument on Rosetta during its mission around the comet. 16O/18O ratios could be determined for O2, methanol, formaldehyde, carbonyl sulfide and sulfur monoxide/dioxide. For O2 the 16O/17O ratio is also available. Some ratios are strongly enriched in the heavy isotopes, especially for sulfur bearing molecules and formaldehyde, whereas for methanol the ratios are compatible with the ones in the solar system. O2 falls in-between, but its oxygen isotopic ratios clearly differ from water, which likely rules out an origin of O2 from water, be it by radiolysis, dismutation during sublimation or the Eley-Rideal process from water ions hitting the nucleus as postulated in the literature.

Published
2020
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8. The Effect of Cosmic Rays on Cometary Nuclei: I Dose deposition

Author

Gronoff, G., Maggiolo, R., Cessateur, G., Moore, W. B., Airapetian, V., De Keyser, J., Dhooghe, F., Gibbons, A., Gunell, H., Mertens, C. J., Rubin, M., and Hosseini, S.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Physics - Space Physics
Abstract

Comets are small bodies thought to contain the most pristine material in the solar system. However, since their formation 4.5 Gy ago, they have been altered by different processes. While not exposed to much electromagnetic radiation, they experience intense particle radiation. Galactic cosmic rays and solar energetic particles have a broad spectrum of energies and interact with the cometary surface and subsurface; they are the main source of space weathering for a comet in the Kuiper Belt or in the Oort cloud; and also affect the ice prior to the comet agglomeration. While low energy particles interact only with the cometary surface, the most energetic ones deposit a significant amount of energy down to tens of meters. This interaction can modify the isotopic ratios in cometary ices and create secondary compounds through radiolysis, such as O2 and H2O2 (paper II: Maggiolo et al., 2020). In this paper, we model the energy deposition of energetic particles as a function of depth using a Geant4 application modified to account for the isotope creation process. We quantify the energy deposited in cometary nucleus by galactic cosmic rays and solar energetic particles. The consequences of the energy deposition on the isotopic and chemical composition of cometary ices and their implication on the interpretation of cometary observations, notably of 67P/Churyumov Gerasimenko by the ESA/Rosetta spacecraft, will be discussed in Paper II.

Published
2020
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9. ROSINA ion zoo at Comet 67P

Author

Beth, A., Altwegg, K., Balsiger, H., Berthelier, J. -J., Combi, M. R., De Keyser, J., Fiethe, B., Fuselier, S. A., Galand, M., Gombosi, T. I., Rubin, M., and Sémon, T.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The Rosetta spacecraft escorted Comet 67P/Churyumov-Gerasimenko for 2 years along its journey through the Solar System between 3.8 and 1.24~au. Thanks to the high resolution mass spectrometer on board Rosetta, the detailed ion composition within a coma has been accurately assessed in situ for the very first time. Previous cometary missions, such as $\text{Giotto}$, did not have the instrumental capabilities to identify the exact nature of the plasma in a coma because the mass resolution of the spectrometers onboard was too low to separate ion species with similar masses. In contrast, the Double Focusing Mass Spectrometer (DFMS), part of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis on board Rosetta (ROSINA), with its high mass resolution mode, outperformed all of them, revealing the diversity of cometary ions. We calibrated and analysed the set of spectra acquired by DFMS in ion mode from October 2014 to April 2016. In particular, we focused on the range from 13-39 u$\cdot$q$^{-1}$. The high mass resolution of DFMS allows for accurate identifications of ions with quasi-similar masses, separating $^{13}$C$^+$ from CH$^+$, for instance. We confirm the presence in situ of predicted cations at comets, such as CH$_m^+$ ($m=1-4$), H$_n$O$^+$ ($n=1-3$), O$^+$, Na$^+$, and several ionised and protonated molecules. Prior to Rosetta, only a fraction of them had been confirmed from Earth-based observations. In addition, we report for the first time the unambiguous presence of a molecular dication in the gas envelope of a Solar System body, namely CO$_2^{++}$., Comment: Accepted for publication in A&A

Published
2020
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10. Evidence of ammonium salts in comet 67P as explanation for the nitrogen depletion in cometary comae

Author

Altwegg, K., Balsiger, H., Berthelier, J. -J., Briois, C., Combi, M., Cottin, H., De Keyser, J., Dhooghe, F., Fiethe, B., Fuselier, S. A., Gombosi, T. I., Hänni, N., Rubin, M., Schuhmann, M., Schroeder, I., Sémon, T., and Wampfler, S.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Cometary comae are generally depleted in nitrogen. The main carriers for volatile nitrogen in comets are NH3 and HCN. It is known that ammonia readily combines with many acids like e.g. HCN, HNCO, HCOOH, etc. encountered in the interstellar medium as well as in cometary ice to form ammonium salts (NH4+X-) at low temperatures. Ammonium salts, which can play a significant role in prebiotic chemistry, are hard to detect in space as they are unstable in the gas phase and their infrared signature is often hidden by thermal radiation or by e.g. OH in minerals. Here we report the presence of all possible sublimation products of five different ammonium salts at comet 67P/Churyumov-Gerasimenko measured by the ROSINA instrument on Rosetta. The relatively high sublimation temperatures of the salts leads to an apparent lack of volatile nitrogen in the coma. This then also explains the observed trend of higher NH3/H2O ratios with decreasing perihelion distances in comets.

Published
2019

11. Cometary plasma science: Open science questions for future space missions

Author

Goetz, C., Gunell, H., Volwerk, M., Beth, A., Eriksson, A., Galand, M., Henri, P., Nilsson, H., Wedlund, C. Simon, Alho, M., Andersson, L., Andre, N., De Keyser, J., Deca, J., Ge, Y., Glassmeier, K.-H., Hajra, R., Karlsson, T., Kasahara, S., Kolmasova, I., LLera, K., Madanian, H., Mann, I., Mazelle, C., Odelstad, E., Plaschke, F., Rubin, M., Sanchez-Cano, B., Snodgrass, C., and Vigren, E.

Published
2022
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12. The detection of ultra-relativistic electrons in low Earth orbit

Author

Katsiyannis, A. C., Dominique, M., Pierrard, V., Rosson, G. Lopez, De Keyser, J., Berghmans, D., Kruglanski, M., Dammasch, I. E., and De Donder, E.

Subjects
Physics - Space Physics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Aims. To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed. Methods. We present an analysis of energetic particles, indirectly detected by the Large Yield RAdiometer (LYRA) instrument on board ESA's Project for On-board Autonomy 2 (PROBA2) satellite as background signal. Combining Energetic Particle Telescope (EPT) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV. Results. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. They are also well confined geographically within the L=4-6 McIlwain zone, which makes it possible to identify their source. Conclusions. Although highly energetic particles are commonly perturbing data acquisition of space instruments, we show in this work that ultra-relativistic electrons with energies in the range of 2-8 MeV are detected only at high latitudes, while not present in the South Atlantic Anomaly region., Comment: Topical Issue: Flares, CMEs and SEPs and their space weather impacts; 20 pages; 7 figures; Presented during 13th European Space Weather Week, 2016

Published
2017
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13. Evidence for depletion of heavy silicon isotopes at comet 67P/Churyumov-Gerasimenko

Author

Rubin, M., Altwegg, K., Balsiger, H., Berthelier, J. -J., Bieler, A., Calmonte, U., Combi, M., De Keyser, J., Engrand, C., Fiethe, B., Fuselier, S. A., Gasc, S., Gombosi, T. I., Hansen, K. C., Hässig, M., Roy, L. Le, Mezger, K., Tzou, C. -Y., Wampfler, S. F., and Wurz, P.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

Context. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) was designed to measure the composition of the gas in the coma of comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. In addition to the volatiles, ROSINA measured refractories sputtered off the comet by the interaction of solar wind protons with the surface of the comet. Aims. The origin of different solar system materials is still heavily debated. Isotopic ratios can be used to distinguish between different reservoirs and investigate processes occurring during the formation of the solar system. Methods. ROSINA consisted of two mass spectrometers and a pressure sensor. In the ROSINA Double Focusing Mass Spectrometer (DFMS), the neutral gas of cometary origin was ionized and then deflected in an electric and a magnetic field that separated the ions based on their mass-to-charge ratio. The DFMS had a high mass resolution, dynamic range, and sensitivity that allowed detection of rare species and the known major volatiles. Results. We measured the relative abundance of all three stable silicon isotopes with the ROSINA instrument on board the Rosetta spacecraft. Furthermore, we measured $^{13}$C/$^{12}$C in C$_2$H$_4$, C$_2$H$_5$, and CO. The DFMS in situ measurements indicate that the average silicon isotopic composition shows depletion in the heavy isotopes $^{29}$Si and $^{30}$Si with respect to $^{28}$Si and solar abundances, while $^{13}$C to $^{12}$C is analytically indistinguishable from bulk planetary and meteorite compositions. Although the origin of the deficiency of the heavy silicon isotopes cannot be explained unambiguously, we discuss mechanisms that could have contributed to the measured depletion of the isotopes $^{29}$Si and $^{30}$Si., Comment: Accepted for publication in Astronomy & Astrophysics

Published
2017
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14. Impact of radiogenic heating on the formation conditions of comet 67P/Churyumov-Gerasimenko

Author

Mousis, O., Drouard, A., Vernazza, P., Lunine, J. I., Monnereau, M., Maggiolo, R., Altwegg, K., Balsiger, H., Berthelier, J. -J., Cessateur, G., De Keyser, J., Fuselier, S. A., Gasc, S., Korth, A., Deun, T. Le, Mall, U., Marty, B., Rème, H., Rubin, M., Tzou, C. -Y., Waite, J. H., and Wurz, P.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Because of the high fraction of refractory material present in comets, the heat produced by the radiogenic decay of elements such as aluminium and iron can be high enough to induce the loss of ultravolatile species such as nitrogen, argon or carbon monoxide during their accretion phase in the protosolar nebula. Here, we investigate how heat generated by the radioactive decay of 26Al and 60Fe influences the formation of comet 67P/Churyumov-Gerasimenko, as a function of its accretion time and size of parent body. We use an existing thermal evolution model that includes various phase transitions, heat transfer in the ice-dust matrix, and gas diffusion throughout the porous material, based on thermodynamic parameters derived from Rosetta observations. Two possibilities are considered: either, to account for its bilobate shape, 67P/Churyumov-Gerasimenko was assembled from two primordial ~2 kilometer-sized planetesimals, or it resulted from the disruption of a larger parent body with a size corresponding to that of comet Hale-Bopp (~70 km). To fully preserve its volatile content, we find that either 67P/Churyumov-Gerasimenko's formation was delayed between ~2.2 and 7.7 Myr after that of Ca-Al-rich Inclusions in the protosolar nebula or the comet's accretion phase took place over the entire time interval, depending on the primordial size of its parent body and the composition of the icy material considered. Our calculations suggest that the formation of 67P/Churyumov-Gerasimenko is consistent with both its accretion from primordial building blocks formed in the nebula or from debris issued from the disruption of a Hale-Bopp-like body., Comment: Accepted for publication in The Astrophysical Journal Letters

Published
2017
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16. Differential kinetic dynamics and heating of ions in the turbulent solar wind

Author

Valentini, F., Perrone, D., Stabile, S., Pezzi, O., Servidio, S., De Marco, R., Marcucci, F., Bruno, R., Lavraud, B., De Keyser, J., Consolini, G., Brienza, D., Sorriso-Valvo, L., Retinò, A., Vaivads, A., Salatti, M., and Veltri, P.

Subjects
Physics - Space Physics
Abstract

The solar wind plasma is a fully ionized and turbulent gas ejected by the outer layers of the solar corona at very high speed, mainly composed by protons and electrons, with a small percentage of helium nuclei and a significantly lower abundance of heavier ions. Since particle collisions are practically negligible, the solar wind is typically not in a state of thermodynamic equilibrium. Such a complex system must be described through self-consistent and fully nonlinear models, taking into account its multi-species composition and turbulence. We use a kinetic hybrid Vlasov-Maxwell numerical code to reproduce the turbulent energy cascade down to ion kinetic scales, in typical conditions of the uncontaminated solar wind plasma, with the aim of exploring the differential kinetic dynamics of the dominant ion species, namely protons and alpha particles. We show that the response of different species to the fluctuating electromagnetic fields is different. In particular, a significant differential heating of alphas with respect to protons is observed. Interestingly, the preferential heating process occurs in spatial regions nearby the peaks of ion vorticity and where strong deviations from thermodynamic equilibrium are recovered. Moreover, by feeding a simulator of a top-hat ion spectrometer with the output of the kinetic simulations, we show that measurements by such spectrometer planned on board the Turbulence Heating ObserveR (THOR mission), a candidate for the next M4 space mission of the European Space Agency, can provide detailed three-dimensional ion velocity distributions, highlighting important non-Maxwellian features. These results support the idea that future space missions will allow a deeper understanding of the physics of the interplanetary medium.

Published
2016
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17. Solar illumination control of ionospheric outflow above polar cap arcs

Author

Maes, L., Maggiolo, R., De Keyser, J., Dandouras, I., Fear, R. C., Fontaine, D., and Haaland, S.

Subjects
Physics - Space Physics
Abstract

We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between We find a clear transition at SZA between $\sim$94$^{\circ}$ and $\sim$107$^{\circ}$, with the O$^{+}$ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O$^{+}$ upflow occurs locally above the polar ionosphere. The same is found for H$^{+}$, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conductivity.

Published
2016
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18. Scale size of cometary bow shocks

Author

Edberg, N. J. T., primary, Eriksson, A.I., additional, Vigren, E., additional, Nilsson, H., additional, Gunell, H., additional, Götz, C., additional, Richter, I., additional, Henri, P., additional, and De Keyser, J., additional

Published
2024
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19. Scale size of cometary bow shocks

Author

Edberg, Niklas J. T., Eriksson, Anders I., Vigren, Erik, Nilsson, H., Gunell, H., Götz, C., Richter, I., Henri, P., De Keyser, J., Edberg, Niklas J. T., Eriksson, Anders I., Vigren, Erik, Nilsson, H., Gunell, H., Götz, C., Richter, I., Henri, P., and De Keyser, J.

Abstract

Context. In past decades, several spacecraft have visited comets to investigate their plasma environments. In the coming years, Comet Interceptor will make yet another attempt. This time, the target comet and its outgassing activity are unknown and may not be known before the spacecraft has been launched into its parking orbit, where it will await a possible interception. If the approximate outgassing rate can be estimated remotely when a target has been identified, it is desirable to also be able to estimate the scale size of the plasma environment, defined here as the region bound by the bow shock. Aims. This study aims to combine previous measurements and simulations of cometary bow shock locations to gain a better understanding of how the scale size of cometary plasma environments varies. We compare these data with models of the bow shock size, and we furthermore provide an outgassing rate-dependent shape model of the bow shock. We then use this to predict a range of times and cometocentric distances for the crossing of the bow shock by Comet Interceptor, together with expected plasma density measurements along the spacecraft track. Methods. We used data of the location of cometary bow shocks from previous spacecraft missions, together with simulation results from previously published studies. We compared these results with an existing model of the bow shock stand-off distance and expand on this to provide a shape model of cometary bow shocks. The model in particular includes the cometary outgassing rate, but also upstream solar wind conditions, ionisation rates, and the neutral flow velocity. Results. The agreement between the gas-dynamic model and the data and simulation results is good in terms of the stand-off distance of the bow shock as a function of the outgassing rate. For outgassing rates in the range of 1027–1031–s-1, the scale size of cometary bow shocks can vary by four orders of magnitude, from about 102 km to 106 km, for an ionisation rate, flow ve

Published
2024
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20. Oblique Alfv\'en instability driven by compensated currents

Author

Malovichko, P., Voitenko, Y., and De Keyser, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics, Physics - Space Physics
Abstract

Compensated-current systems created by energetic ion beams are widespread in space and astrophysical plasmas. The well-known examples are foreshock regions in the solar wind and around supernova remnants. We found a new oblique Alfv\'enic instability driven by compensated currents flowing along the background magnetic field. Because of the vastly different electron and ion gyroradii, oblique Alfv\'enic perturbations react differently on the currents carried by the hot ion beams and the return electron currents. Ultimately, this difference leads to a non-resonant aperiodic instability at perpendicular wavelengths close to the beam ion gyroradius. The instability growth rate increases with increasing beam current and temperature. In the solar wind upstream of Earth's bow shock the instability growth time can drop below 10 proton cyclotron periods. Our results suggest that this instability can contribute to the turbulence and ion acceleration in space and astrophysical foreshocks., Comment: 6 figures, accepted by ApJ

Published
2013
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21. Electrostatic plasma instabilities driven by neutral gas flows in the solar chromosphere

Author

Gogoberidze, G., Voitenko, Y., Poedts, S., and De Keyser, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics, Physics - Space Physics
Abstract

We investigate electrostatic plasma instabilities of Farley-Buneman (FB) type driven by quasi-stationary neutral gas flows in the solar chromosphere. The role of these instabilities in the chromosphere is clarified. We find that the destabilizing ion thermal effect is highly reduced by the Coulomb collisions and can be ignored for the chromospheric FB-type instabilities. On the contrary, the destabilizing electron thermal effect is important and causes a significant reduction of the neutral drag velocity triggering the instability. The resulting threshold velocity is found as function of chromospheric height. Our results indicate that the FB type instabilities are still less efficient in the global chromospheric heating than the Joule dissipation of the currents driving these instabilities. This conclusion does not exclude the possibility that the FB type instabilities develop in the places where the cross-field currents overcome the threshold value and contribute to the heating locally. Typical length-scales of plasma density fluctuations produced by these instabilities are determined by the wavelengths of unstable modes, which are in the range $10-10^2$ cm in the lower chromosphere, and $10^2-10^3$ cm in the upper chromosphere. These results suggest that the decimetric radio waves undergoing scattering (scintillations) by these plasma irregularities can serve as a tool for remote probing of the solar chromosphere at different heights., Comment: 9 pages, 4 figures, submitted to MNRAS

Published
2013
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25. Rivaroxaban or aspirin for patent foramen ovale and embolic stroke of undetermined source: a prespecified subgroup analysis from the NAVIGATE ESUS trial

Author

Abdelhamid, N, Abdul Rahman, D, Abdul-Saheb, M, Abreu, P, Abroskina, M, Abu Ahmad, F, Accassat, S, Acciaresi, M, Adami, A, Ahmad, N, Ahmed, F, Alberto Hawkes, M, Alemseged, F, Ali, A, Altavilla, R, Alwis, L, Amarenco, P, Amaro, S, Amaya Sanchez, LE, Amelia Pinto, A, Ameriso, SF, Amin, H, Amino, T, Amjad, AK, Anagnostou, E, Andersen, G, Anderson, C, Anderson, DC, Andrea Falco, M, Andres Mackinnon, F, Andreu, D, Androulakis, M, Angel Gamero, M, Angel Saredo, G, Angeles Diaz, R, Angels Font, M, Anticoli, S, Arauz, A, Arauz Gongora, AA, Araya, P, Arenillas Lara, JF, Arias Rivas, S, Arnold, M, Augustin, S, Avelar, W, Azevedo, E, Babikian, V, Bacellar, A, Badalyan, K, Bae, HJ, Baez Martinez, EM, Bagelmann, H, Bailey, P, Bak, Z, Baker, M, Balazs, A, Baldaranov, D, Balogun, I, Balueva, T, Bankuti, Z, Bar, M, Baranowska, A, Bardutzky, J, Barker Trejo, S, Barlinn, J, Baronnet, F, Barroso, C, Barteys, M, Bartolottiova, T, Barulin, A, Bas, M, Bashir, S, Basile, V, Bathe-Peters, R, Bathula, R, Batista, C, Batur Caglayan, H, Baumgartner, P, Bazan, R, Bazhenova, O, Beaudry, M, Beer, J, Behnam, Y, Beilei, C, Beinlich, A, Bejot, Y, Belkin, A, Benavente, OR, Benjamin, A, Berardi, V, Bereczki, D, Berkowitz, SD, Berlingieri, J, Berrios, W, Berrouschot, J, Bhandari, M, Bhargavah, M, Bicker, H, Bicsak, T, Bilik, M, Bindila, D, Birchenall, J, Birnbaum, L, Black, T, Blacker, D, Blacquiere, D, Blanc-Labarre, C, Blank, C, Blazejewska-Hyzorek, B, Bloch, S, Bodiguel, E, Bogdanov, E, Boos, L, Borcsik, L, Bornstein, N, Bouly, S, Braga, G, Bragado, I, Bravi, MC, Brokalaki, C, Brola, W, Brouns, R, Bruce, D, Brzoska-Mizgalska, J, Buck, B, Buksinska-Lisik, M, Burke, J, Burn, M, Bustamante, G, Cabrejo, L, Cai, K, Cajaraville, S, Calejo, M, Calvet, D, Campillo, J, Campos Costa, E, Camps, P, Can Alaydin, H, Candeloro, E, Canepa, C, Cantu Brito, CG, Cappellari, M, Carcel, C, Cardona Portela, P, Cardoso, F, Carek, M, Carletti, M, Carlos Portilla, J, Caruso, P, Casado-Naranjo, I, Castellini, P, 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Krassen, Perera, Kanjana, Santo, Gustavo, Olavarria, Veronica, Lindgren, Arne, Bangdiwala, Shrikant, Shoamanesh, Ashkan, Berkowitz, Scott D, Mundl, Hardi, Connolly, Stuart J, and Hart, Robert G

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2018
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26. D₂O and HDS in the coma of 67P/Churyumov—Gerasimenko

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Altwegg, K., Balsiger, H., Berthelier, J. J., Bieler, A., Calmonte, U., De Keyser, J., Fiethe, B., Fuselier, S. A., Gasc, S., Gombosi, T. I., Owen, T., Le Roy, L., Rubin, M., Sémon, T., and Tzou, C.-Y.

Published
2017

27. Xenon isotopes in 67P/Churyumov-Gerasimenko show that comets contributed to Earth's atmosphere

Author

Marty, B., Altwegg, K., Balsiger, H., Bar-Nun, A., Bekaert, D. V., Berthelier, J.-J., Bieler, A., Briois, C., Calmonte, U., Combi, M., De Keyser, J., Fiethe, B., Fuselier, S. A., Gasc, S., Gombosi, T. I., Hansen, K. C., Hässig, M., Jäckel, A., Kopp, E., Korth, A., Le Roy, L., Mall, U., Mousis, O., Owen, T., Rème, H., Rubin, M., Sémon, T., Tzou, C.-Y., Waite, J. H., and Wurz, P.

Published
2017

29. Estimated GFR and the Effect of Intensive Blood Pressure Lowering After Acute Intracerebral Hemorrhage

Author

Anderson, C.S., Chalmers, J., Arima, H., Davis, S., Heeley, E., Huang, Y., Lavados, P., Neal, B., Parsons, M.W., Lindley, R., Morgenstern, L., Robinson, T., Stapf, C., Tzourio, C., Wang, J.G., Chen, S., Chen, X.Y., Cui, L., Liu, Z., Lu, C., Wang, J., Wu, S., Xu, E., Yang, Q., Zhang, C., Zhang, J., Beer, R., Schmutzhard, E., Redondo, P., Kaste, M., Soinne, L., Tatlisumak, T., Wartenberg, K., Ricci, S., Klijn, K., Azevedo, E., Chamorro, A., Arnold, M., Fischer, U., Kaul, S., Pandian, J., Boyini, H., Singh, S., Rabinstein, A.A., Estol, C., Silva, G., Olavarria, V.V., Robinson, T.G., Simes, R.J., Bousser, M.-G., Hankey, G., Jamrozik, K., Johnston, S.C., Li, S., Bailey, K., Cheung, T., Delcourt, C., Chintapatla, S., Ducasse, E., Erho, T., Hata, J., Holder, B., Knight, E., Leroux, M., Sassé, T., Odgers, E., Walsh, R., Wolfowicz, Z., Chen, G., Fuentes, S., Peng, B., Schneble, H.-M., Wang, M.-X., Billot, L., Heritier, S., Li, Q., Woodward, M., Abimbola, S., Anderson, S., Chan, E., Cheng, G., Chmielnik, P., Leighton, S., Liu, J.-Y., Rasmussen, B., Saxena, A., Tripathy, S., Armenis, M., Baig, M.A., Naidu, B., Starzec, G., Steley, S., Moles, A., Ruiz, A., Zimmermann, M., Marinho, J., Alves, S., Angelim, R., Araujo, J., Kawakami, L., Bustos, C., Gonzalez, F., Munoz Venturelli, P., Chen, X., Jia, R., Li, N., Qu, S., Shu, Y., Song, A., Sun, J., Xiao, J., Zhao, Y., Huang, Q., Vicaut, E., Chamam, A., Viaud, M.-C., Dert, C., Fiedler, U., Jovis, V., Kabla, S., Marchand, S., Pena, A., Rochaud, V., Mallikarjuna, K., Hasan, N., Berge, E., Sandset, E.C., Forårsveen, A.S., Richardson, D., Kumar, T., Lewin, S., Poulter, N., Field, J., Anjum, A., Wilson, A., Perelmuter, H., Agarie, A.M., Barboza, A.G., Recchia, L.A., Miranda, I.F., Rauek, S.G., Duplessis, R.J., Dewey, H., Walker, L., Petrolo, S., Bladin, C., Sturm, J., Crimmins, D., Griffiths, D., Schutz, A., Zenteno, V., Miteff, F., Spratt, N., Kerr, E., Levi, C.R., Phan, T.G., Ma, H., Sanders, L., Moran, C., Wong, K., Read, S., Henderson, R., Wong, A., Hull, R., Skinner, G., Hand, P., Yan, B., Tu, H., Campbell, B., Blacker, D.J., Wijeratne, T., Pathirage, M., Jasinararchchi, M., Matkovic, Z., Celestino, S., Gruber, F., Vosko, M.R., Diabl, E., Rathmaier, S., Pfausler, B., Helbok, R., Fazekas, F., Fischer, R., Poltrum, B., Zechner, B., Trummer, U., Rutgers, M.P., Peeters, A., Dusart, A., Duray, M.-C., Parmentier, C., Ferrao-Santos, S., Brouns, R., De Raedt, S., De Smedt, A., VanHooff, R.-J., De Keyser, J., Martins, S.C.O., de Almeida, A.G., Broudani, R., Titton, N.F., de Freitas, G.R., Cardoso, F.M., Giesel, L.M., Lima, N.A., Jr, Ferraz de Almeida, A.C., Gomes, R.B., Borges dos Santos, T.S., Veloso Soares, E.M., Neto, O.L.A., Silva, G.S., Gomes, D.L., de Carvalho, F.A., Miranda, M., Marques, A., Zétola, V.F., de Matia, G., Lange, M.C., Montes, J., Reccius, A., Soto, A., Rivas, R., Klapp, C., Illanes, S., Aguilera, C., Castro, A., Figueroa, C., Benavides, J., Salamanca, P., Concha, M.C., Pajarito, J., Araya, P., Guerra, F., Li, Y., Liu, G., Wang, B., Chong, Y., He, M., Wang, L., Liu, J., Zhang, X., Lai, C., Jiang, H., Cui, S., Tao, Q., Zhang, Y., Yao, S., Xu, M., Xiao, H., Hu, J., Tang, J., Ji, H., Jiang, M., Yu, F., Yang, X., Guo, X., Wang, Y., Wu, L., Gao, Y., Sun, D., Huang, X., Liu, L., Li, P., Jiang, Y., Li, H., Lu, H., Zhou, J., Yuan, C., Qi, X., Qiu, F., Qian, H., Wang, W., Sun, W., Li, F., Liu, R., Peng, Q., Ren, Z., Fan, C., Wang, H., Wang, T., Shi, F., Duan, C., Chen, Z., Tan, X., Zhao, Z., Chen, J., Han, T., Zhang, L., Hu, Q., Hou, Q., Zhao, X., Zeng, G., Ma, L., Wang, F., Zeng, L., Guo, Z., Fu, Y., Song, Y., Tai, L., Liu, X., Su, X., Yang, Y., Dong, R., Xu, Y., Tian, S., Cheng, S., Su, L., Xie, X., Xu, T., Geng, D., Yan, X., Fan, H., Zhao, N., Wang, S., Yang, J., Yan, M., Li, L., Li, Z., Xu, X., Lian, Y., Sun, H., Liu, D., Wang, N., Tang, Q., Han, Z., Feng, L., Cui, Y., Tian, J., Chang, H., Sun, X., Liu, C., Wen, Z., Lin, Q., Sun, L., Hu, B., Zou, M., Bao, Q., Lin, X., Zhao, L., Tian, X., Wang, X., Li, X., Hao, L., Duan, Y., Wang, R., Wei, Z., Ren, S., Ren, H., Dong, Y., Cheng, Y., Liu, W., Han, J., Zhang, Z., Zhu, J., Qian, J., Sun, Y., Liu, K., Long, F., Peng, X., Zhang, Q., Yuan, Z., Wang, C., Huang, M., He, P., You, Y., Xia, J., Zhou, L., Hou, Y., Qi, Y., Mei, L., Lu, R., Ping, L., Zhou, S., Zhang, S., Zou, R., Guo, J., Li, M., Wei, W., Curtze, S., Saarela, M., Strbian, D., Scheperjans, F., De Broucker, T., Henry, C., Cumurciuc, R., Ibos-Augé, N., Zéghoudi, A.-C., Pico, F., Dereeper, O., Simian, M.-C., Boisselier, C., Mahfoud, A., Timsit, S., Merrien, F.M., Guillon, B., Sevin, M., Herisson, F., Magne, C., Ameri, A., Cret, C., Stefanizzi, S., Klapzcynski, F., Denier, C., Sarov-Riviere, M., Reiner, P., Mawet, J., Hervé, D., Buffon, F., Touzé, E., Domigo, V., Lamy, C., Calvet, D., Pasquini, M., Alamowitch, S., Favrole, P., Muresan, I.-P., Crozier, S., Rosso, C., Pires, C., Leger, A., Deltour, S., Cordonnier, C., Henon, H., Rossi, C., Zuber, M., Bruandet, M., Tamazyan, R., Join-Lambert, C., Juettler, E., Krause, T., Maul, S., Endres, M., Jungehulsing, G.J., Hennerici, M., Griebe, M., Sauer, T., Knoll, K., Huber, R., Knauer, K., Knauer, C., Raubold, S., Schneider, H., Hentschel, H., Lautenschläger, C., Schimmel, E., Dzialowski, I., Foerch, C., Lorenz, M., Singer, O., Meyer dos Santos, I.M.R., Hartmann, A., Hamann, A., Schacht, A., Schrader, B., Teíchmann, A., Wartenberg, K.E., Mueller, T.J., Jander, S., Gliem, M., Boettcher, C., Rosenkranz, M., Beck, C., Otto, D., Thomalla, G., Cheng, B., Wong, K.S., Leung, T.W., Soo, Y.O.Y., Prabhakar, S., Kesavarapu, S.R., Gajjela, P.K., Chenna, R.R., Ummer, K., Basheer, M., Andipet, A., Jagarlapudi, M.K.M., Mohammed, A.U.R., Pawar, V.G., Eranki, S.S.K., Singh, Y., Akhtar, N., Borah, N.C., Ghose, M., Choudhury, N., Ichaporia, N.R., Shendge, J., Khese, S., Pamidimukkala, V., Inbamuthaiah, P., Nuthakki, S.R., Tagallamudi, N.M.R., Gutti, A.K., Khurana, D., Kesavarapu, P., Jogi, V., Garg, A., Samanta, D., Sarma, G.R.K., Nadig, R., Mathew, T., Anandan, M.A., Caterbi, E., Zini, A., Cavazzuti, M., Casoni, F., Pentore, R., Falzone, F., Mazzoli, T., Greco, L.M., Menichetti, C., Coppola, F., Cenciarelli, S., Gallinella, E., Mattioni, A., Condurso, R., Sicilia, I., Zampolini, M., Corea, F., Barbi, M., Proietti, C., Toni, D., Pieroni, A., Anzini, A., Falcou, A., Demichele, M., Klijn, C.J.M., Tveiten, A., Thortveit, E.T., Pettersen, S., Holand, N., Hitland, B., Johnsen, S.H., Eltoft, A., Wasay, M., Kamal, A., Iqrar, A., Ali, L., Begum, D., Gama, G., Fonseca, L., Moreira, G., Veloso, L.M., Pinheiro, D., Paredes, L., Rozeira, C., Gregorio, T., Segura Martin, T., Ayo, O., Garcia-Garcia, J., Feria Vilar, I., Gómez Fernández, I., Amaro, S., Urra, X., Obach, V., Cervera, A., Silva, Y., Serena, J., Castellanos, M., Terceno, M., Van Eendenburg, C., Weck, A., Findling, O., Lüdi, R., Warburton, E.A., Day, D., Butler, N., Bumanlag, E., Caine, S., Steele, A., Osborn, M., Dodd, E., Murphy, P., Esisi, B., Brown, E., Hayman, R., Baliga, V.K.V., Minphone, M., Kennedy, J., Reckless, I., Pope, G., Teal, R., Michael, K., Manawadu, D., Kalra, L., Lewis, R., Mistry, B., Cattermole, E., Hassan, A., Mandizvidza, L., Bamford, J., Brooks, H., Bedford, C., Whiting, R., Baines, P., Hussain, M., Harvey, M., Fotherby, K., McBride, S., Bourke, P., Morgan, D., Jennings-Preece, K., Price, C., Huntley, S., Riddell, V.E., Storey, G., Lakey, R.L., Subramanian, G., Jenkinson, D., Kwan, J., David, O., Tiwari, D., James, M., Keenan, S., Eastwood, H., Shaw, L., Kaye, P., Button, D., Madigan, B., Williamson, D., Dixit, A., Davis, J., Hossain, M.O., Ford, G.A., Parry-Jones, A., O'Loughlin, V., Jarapa, R., Naing, Z., Lovelock, C., O'Reilly, J., Khan, U., Bhalla, A., Rudd, A., Birns, J., Werring, D.J., Law, R., Perry, R., Jones, I., Erande, R., Roffe, C., Natarajan, I., Ahmad, N., Finney, K., Lucas, J., Mistri, A., Eveson, D., Marsh, R., Haunton, V., Fugate, J.E., Lepore, S.W., Zheng, Danni, Sato, Shoichiro, Arima, Hisatomi, Heeley, Emma, Delcourt, Candice, Cao, Yongjun, Chalmers, John, and Anderson, Craig S.

Published
2016
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32. Molecular nitrogen in comet 67P/Churyumov-Gerasimenko indicates a low formation temperature

Author

Rubin, M., Altwegg, K., Balsiger, H., Bar-Nun, A., Berthelier, J.-J., Bieler, A., Bochsler, P., Briois, C., Calmonte, U., Combi, M., De Keyser, J., Dhooghe, F., Eberhardt, P., Fiethe, B., Fuselier, S. A., Gasc, S., Gombosi, T. I., Hansen, K. C., Hässig, M., Jäckel, A., Kopp, E., Korth, A., Le Roy, L., Mall, U., Marty, B., Mousis, O., Owen, T., Réme, H., Sémon, T., Tzou, C.-Y., Waite, J. H., and Wurz, P.

Published
2015

33. Estimation of the total oxygen loss from Earth with a semi-empirical model of atmospheric escape

Author

Alonso Tagle, M., Maggiolo, R., Gunell, H., Cessateur, G., De Keyser, J., Lapenta, G., Pierrard, V., and Vandaele, A.

Abstract

Understanding atmospheric escape into space for stellar and planetary conditions differing from the current ones on Earth is an ongoing challenge. It helps us to assess the stability of planetary atmospheres, hence their habitability. Over geological time scales, despite the small changes in Earth’s magnetic field magnitude, the solar wind pressure, and EUV radiation from the Sun have evolved significantly, affecting the atmospheric erosion rate. On one hand, the solar wind pressure affects non-thermal processes, and on the other EUV radiation alters Earth’s atmospheric parameters, increasing the ion production rate and the exospheric temperature. Both jointly cause a significant effect on erosion.We developed a semi-empirical model to analyze seven different erosion mechanisms and their dependency on terrestrial and solar parameters, in order to estimate the oxygen escape rate for past conditions. Our model considers variations of the Earth’s magnetic moment, the solar wind pressure, and the solar EUV flux. We discuss the effect of different atmospheric factors and their impact on the oxygen loss for each escape process and provide an estimate of the total amount of oxygen lost by the Earth over the last ~2 billion years. In addition, such a model contributes to identifying the solar and planetary parameters that are critical for the stability of the planet’s atmosphere., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023
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37. Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko

Author

Hässig, M., Altwegg, K., Balsiger, H., Bar-Nun, A., Berthelier, J. J., Bieler, A., Bochsler, P., Briois, C., Calmonte, U., Combi, M., De Keyser, J., Eberhardt, P., Fiethe, B., Fuselier, S. A., Galand, M., Gasc, S., Gombosi, T. I., Hansen, K. C., Jäckel, A., Keller, H. U., Kopp, E., Korth, A., Kührt, E., Le Roy, L., Mall, U., Marty, B., Mousis, O., Neefs, E., Owen, T., Rème, H., Rubin, M., Sémon, T., Tornow, C., Tzou, C.-Y., Waite, J. H., and Wurz, P.

Published
2015

38. 67P/Churyumov-Gerasimenko, a Jupiter family comet with a high D/H ratio

Author

Altwegg, K., Balsiger, H., Bar-Nun, A., Berthelier, J. J., Bieler, A., Bochsler, P., Briois, C., Calmonte, U., Combi, M., De Keyser, J., Eberhardt, P., Fiethe, B., Fuselier, S., Gasc, S., Gombosi, T. I., Hansen, K.C., Hässig, M., Jäckel, A., Kopp, E., Korth, A., LeRoy, L., Mall, U., Marty, B., Mousis, O., Neefs, E., Owen, T., Rème, H., Rubin, M., Sémon, T., Tzou, C.-Y., Waite, H., and Wurz, P.

Published
2015

41. PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS

Author

Dehant, V., Asael, D., Baland, R. M., Baludikay, B. K., Beghin, J., Belza, J., Beuthe, M., Breuer, D., Chernonozhkin, S., Claeys, Ph., Cornet, Y., Cornet, L., Coyette, A., Debaille, V., Delvigne, C., Deproost, M. H., De WInter, N., Duchemin, C., El Atrassi, F., François, C., De Keyser, J., Gillmann, C., Gloesener, E., Goderis, S., Hidaka, Y., Höning, D., Huber, M., Hublet, G., Javaux, E. J., Karatekin, Ö., Kodolanyi, J., Revilla, L. Lobo, Maes, L., Maggiolo, R., Mattielli, N., Maurice, M., McKibbin, S., Morschhauser, A., Neumann, W., Noack, L., Pham, L. B. S., Pittarello, L., Plesa, A. C., Rivoldini, A., Robert, S., Rosenblatt, P., Spohn, T., Storme, J. -Y., Tosi, N., Trinh, A., Valdes, M., Vandaele, A. C., Vanhaecke, F., Van Hoolst, T., Van Roosbroek, N., Wilquet, V., and Yseboodt, M.

Published
2016
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42. Magnetopause and Boundary Layer

Author

De Keyser, J., Dunlop, M. W., Owen, C. J., Sonnerup, B. U. Ö., Haaland, S. E., Vaivads, A., Paschmann, G., Lundin, R., Rezeau, L., Paschmann, G., editor, Schwartz, S. J., editor, Escoubet, C. P., editor, and Haaland, S., editor

Published
2005
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49. Abundant molecular oxygen in the coma of comet 67P/Churyumov-Gerasimenko

Author

Bieler, A., Altwegg, K., Balsiger, H., Bar-Nun, A., Berthelier, J.-J., Bochsler, P., Briois, C., Calmonte, U., Combi, M., De Keyser, J., van Dishoeck, E.F., Fiethe, B., Fuselier, S.A., Gasc, S., Gombosi, T.I., Hansen, K.C., Hassig, M., Jackel, A., Kopp, E., Korth, A., Roy, L. Le, Mall, U., Maggiolo, R., Marty, B., Mousis, O., Owen, T., Reme, H., Rubin, M., Semon, T., Tzou, C.-Y., Waite, J.H., Walsh, C., and Wurz, P.

Subjects
Comets -- Chemical properties -- Observations, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

The composition of the neutral gas comas of most comets is dominated by [H.sub.2]O, CO and C[O.sub.2], typically comprising as much as 95 per cent of the total gas density (1). In addition, cometary comas have been found to contain a rich array of other molecules, including sulfuric compounds and complex hydrocarbons. Molecular oxygen ([O.sub.2]), however, despite its detection on other icy bodies such as the moons of Jupiter and Saturn (2,3), has remained undetected in cometary comas. Here we report in situ measurement of [O.sub.2] in the coma of comet 67P/Churyumov-Gerasimenko, with local abundances ranging from one per cent to ten per cent relative to [H.sub.2]O and with a mean value of 3.80 ± 0.85 per cent. Our observations indicate that the [O.sub.2]/[H.sub.2]O ratio is isotropic in the coma and does not change systematically with heliocentric distance. This suggests that primordial [O.sub.2] was incorporated into the nucleus during the comet's formation, which is unexpected given the low upper limits from remote sensing observations (4). Current Solar System formation models do not predict conditions that would allow this to occur., Measurements of the coma of 67P/Churyumov-Gerasimenko (hereafter 67P) were made between September 2014 and March 2015 with the ROSINA-DFMS mass spectrometer (5) on board the Rosetta spacecraft. For the present [...]

Published
2015

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