@misc{GruendePaterShowalteretal.2006, author = {Gr{\"u}n, Eberhard and de Pater, Imke and Showalter, Mark and Spahn, Frank and Srama, Ralf}, title = {Physics of dusty rings: History and perspective}, series = {Planetary and space science}, volume = {54}, journal = {Planetary and space science}, number = {9-10}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-0633}, doi = {10.1016/j.pss.2006.05.005}, pages = {837 -- 843}, year = {2006}, language = {en} } @article{HsuSchmidtKempfetal.2018, author = {Hsu, Hsiang-Wen and Schmidt, J{\"u}rgen and Kempf, Sascha and Postberg, Frank and Moragas-Klostermeyer, Georg and Seiss, Martin and Hoffmann, Holger and Burton, Marcia and Ye, ShengYi and Kurth, William S. and Horanyi, Mihaly and Khawaja, Nozair and Spahn, Frank and Schirdewahn, Daniel and Moore, Luke and Cuzzi, Jeff and Jones, Geraint H. and Srama, Ralf}, title = {In situ collection of dust grains falling from Saturn's rings into its atmosphere}, series = {Science}, volume = {362}, journal = {Science}, number = {6410}, publisher = {American Assoc. for the Advancement of Science}, address = {Washington}, issn = {0036-8075}, doi = {10.1126/science.aat3185}, pages = {49 -- +}, year = {2018}, abstract = {Saturn's main rings are composed of >95\% water ice, and the nature of the remaining few percent has remained unclear. The Cassini spacecraft's traversals between Saturn and its innermost D ring allowed its cosmic dust analyzer (CDA) to collect material released from the main rings and to characterize the ring material infall into Saturn. We report the direct in situ detection of material from Saturn's dense rings by the CDA impact mass spectrometer. Most detected grains are a few tens of nanometers in size and dynamically associated with the previously inferred "ring rain." Silicate and water-ice grains were identified, in proportions that vary with latitude. Silicate grains constitute up to 30\% of infalling grains, a higher percentage than the bulk silicate content of the rings.}, language = {en} } @article{SpahnSchmidtAlbersetal.2006, author = {Spahn, Frank and Schmidt, J{\"u}rgen and Albers, Nicole and H{\"o}rning, Marcel and Makuch, Martin and Seiß, Martin and Kempf, Sascha and Srama, Ralf and Dikarev, Valeri and Helfert, Stefan and Moragas-Klostermeyer, Georg and Krivov, Alexander V. and Sremcevic, Miodrag and Tuzzolino, Anthony J. and Economou, Thanasis and Gr{\"u}n, Eberhard}, title = {Cassini dust measurements at Enceladus and implications for the origin of the E ring}, doi = {10.1126/science.1121375}, year = {2006}, language = {en} } @article{SramaAhrensAltobellietal.2004, author = {Srama, Ralf and Ahrens, Thomas J. and Altobelli, Nicolas and Auer, S. and Bradley, J. G. and Burton, M. and Dikarev, V. V. and Economou, T. and Fechtig, Hugo and G{\"o}rlich, M. and Grande, M. and Graps, Amara and Gr{\"u}n, Eberhard and Havnes, Ove and Helfert, Stefan and Horanyi, Mihaly and Igenbergs, E. and Jessberger, Elmar K. and Johnson, T. V. and Kempf, Sascha and Krivov, Alexander v. and Kr{\"u}ger, Harald and Mocker-Ahlreep, Anna and Moragas-Klostermeyer, Georg and Lamy, Philippe and Landgraf, Markus and Linkert, Dietmar and Linkert, G. and Lura, F. and McDonnell, J. A. M. and Moehlmann, Dirk and Morfill, Gregory E. and Muller, M. and Roy, M. and Schafer, G. and Schlotzhauer, G. and Schwehm, Gerhard H. and Spahn, Frank and St{\"u}big, M. and Svestka, Jiri and Tschernjawski, V}, title = {The Cassini Cosmic Dust Analyzer}, issn = {0038-6308}, year = {2004}, abstract = {The Cassini-Huygens Cosmic Dust Analyzer (CDA) is intended to provide direct observations of dust grains with masses between 10(-19) and 10(-9) kg in interplanetary space and in the jovian and saturnian systems, to investigate their physical, chemical and dynamical properties as functions of the distances to the Sun, to Jupiter and to Saturn and its satellites and rings, to study their interaction with the saturnian rings, satellites and magnetosphere. Chemical composition of interplanetary meteoroids will be compared with asteroidal and cometary dust, as well as with Saturn dust, ejecta from rings and satellites. Ring and satellites phenomena which might be effects of meteoroid impacts will be compared with the interplanetary dust environment. Electrical charges of particulate matter in the magnetosphere and its consequences will be studied, e.g. the effects of the ambient plasma and the magnetic held on the trajectories of dust particles as well as fragmentation of particles due to electrostatic disruption. The investigation will be performed with an instrument that measures the mass, composition, electric charge, speed, and flight direction of individual dust particles. It is a highly reliable and versatile instrument with a mass sensitivity 106 times higher than that of the Pioneer 10 and I I dust detectors which measured dust in the saturnian system. The Cosmic Dust Analyzer has significant inheritance from former space instrumentation developed for the VEGA, Giotto, Galileo, and Ulysses missions. It will reliably measure impacts from as low as I impact per month up to 104 impacts per second. The instrument weighs 17 kg and consumes 12 W, the integrated time-of-flight mass spectrometer has a mass resolution of up to 50. The nominal data transmission rate is 524 bits/s and varies between 50 and 4192 bps}, language = {en} } @article{YeKurthHospodarskyetal.2018, author = {Ye, S. -Y. and Kurth, William S. and Hospodarsky, George B. and Persoon, Ann M. and Gurnett, Don A. and Morooka, Michiko and Wahlund, Jan-Erik and Hsu, Hsiang-Wen and Seiss, Martin and Srama, Ralf}, title = {Cassini RPWS dust observation near the Janus/Epimetheus orbit}, series = {Journal of geophysical research : Space physics}, volume = {123}, journal = {Journal of geophysical research : Space physics}, number = {6}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1029/2017JA025112}, pages = {4952 -- 4960}, year = {2018}, abstract = {During the Ring Grazing orbits near the end of Cassini mission, the spacecraft crossed the equatorial plane near the orbit of Janus/Epimetheus (similar to 2.5 Rs). This region is populated with dust particles that can be detected by the Radio and Plasma Wave Science (RPWS) instrument via an electric field antenna signal. Analysis of the voltage waveforms recorded on the RPWS antennas provides estimations of the density and size distribution of the dust particles. Measured RPWS profiles, fitted with Lorentzian functions, are shown to be mostly consistent with the Cosmic Dust Analyzer, the dedicated dust instrument on board Cassini. The thickness of the dusty ring varies between 600 and 1,000 km. The peak location shifts north and south within 100 km of the ring plane, likely a function of the precession phase of Janus orbit.}, language = {en} } @article{YeKurthHospodarskyetal.2018, author = {Ye, Shengyi and Kurth, William S. and Hospodarsky, George B. and Persoon, Ann M. and Sulaiman, Ali H. and Gurnett, Don A. and Morooka, Michiko and Wahlund, Jan-Erik and Hsu, Hsiang-Wen and Sternovsky, Zoltan and Wang, Xu and Horanyi, M. and Seiss, Martin and Srama, Ralf}, title = {Dust Observations by the Radio and Plasma Wave Science Instrument During}, series = {Geophysical research letters}, volume = {45}, journal = {Geophysical research letters}, number = {19}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1029/2018GL078059}, pages = {10101 -- 10109}, year = {2018}, abstract = {Plain Language Summary Cassini flew through the gap between Saturn and its rings for 22 times before plunging into the atmosphere of Saturn, ending its 20-year mission. The radio and plasma waves instrument on board Cassini helped quantify the dust hazard in this previously unexplored region. The measured density of large dust particles was much lower than expected, allowing high-value science observations during the subsequent Grand Finale orbits.}, language = {en} } @article{CuzziBurnsCharnozetal.2010, author = {Cuzzi, Jeff N. and Burns, Joseph A. and Charnoz, S{\´e}bastien and Clark, Roger N. and Colwell, Josh E. and Dones, Luke and Esposito, Larry W. and Filacchione, Gianrico and French, Richard G. and Hedman, Matthew M. and Kempf, Sascha and Marouf, Essam A. and Murray, Carl D. and Nicholson, Phillip D. and Porco, Carolyn C. and Schmidt, J{\"u}rgen and Showalter, Mark R. and Spilker, Linda J. and Spitale, Joseph N. and Srama, Ralf and Sremcević, Miodrag and Tiscareno, Matthew Steven and Weiss, John}, title = {An evolving view of Saturn's dynamic rings}, issn = {0036-8075}, doi = {10.1126/science.1179118}, year = {2010}, abstract = {We review our understanding of Saturn's rings after nearly 6 years of observations by the Cassini spacecraft. Saturn's rings are composed mostly of water ice but also contain an undetermined reddish contaminant. The rings exhibit a range of structure across many spatial scales; some of this involves the interplay of the fluid nature and the self-gravity of innumerable orbiting centimeter- to meter-sized particles, and the effects of several peripheral and embedded moonlets, but much remains unexplained. A few aspects of ring structure change on time scales as short as days. It remains unclear whether the vigorous evolutionary processes to which the rings are subject imply a much younger age than that of the solar system. Processes on view at Saturn have parallels in circumstellar disks.}, language = {en} } @article{PostbergKempfSchmidtetal.2009, author = {Postberg, Frank and Kempf, Sascha and Schmidt, J{\"u}rgen and Brilliantov, Nikolai V. and Beinsen, Alexander and Abel, Bernd and Buck, Udo and Srama, Ralf}, title = {Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus}, issn = {0028-0836}, doi = {10.1038/Nature08046}, year = {2009}, abstract = {Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole(1-5), suggesting the possibility of a subsurface ocean(5-7). These plume particles are the dominant source of Saturn's E ring(7,8). A previous in situ analysis(9) of these particles concluded that the minor organic or siliceous components, identified in many ice grains, could be evidence for interaction between Enceladus' rocky core and liquid water(9,10). It was not clear, however, whether the liquid is still present today or whether it has frozen. Here we report the identification of a population of E-ring grains that are rich in sodium salts (similar to 0.5- 2\% by mass), which can arise only if the plumes originate from liquid water. The abundance of various salt components in these particles, as well as the inferred basic pH, exhibit a compelling similarity to the predicted composition of a subsurface Enceladus ocean in contact with its rock core(11). The plume vapour is expected to be free of atomic sodium. Thus, the absence of sodium from optical spectra(12) is in good agreement with our results. In the E ring the upper limit for spectroscopy(12) is insufficiently sensitive to detect the concentrations we found.}, language = {en} } @article{PostbergSchmidtHillieretal.2011, author = {Postberg, Frank and Schmidt, J. and Hillier, J. and Kempf, Sascha and Srama, Ralf}, title = {A salt-water reservoir as the source of a compositionally stratified plume on Enceladus}, series = {Nature : the international weekly journal of science}, volume = {474}, journal = {Nature : the international weekly journal of science}, number = {7353}, publisher = {Nature Publ. Group}, address = {London}, issn = {0028-0836}, doi = {10.1038/nature10175}, pages = {620 -- 622}, year = {2011}, abstract = {The discovery of a plume of water vapour and ice particles emerging from warm fractures ('tiger stripes') in Saturn's small, icy moon Enceladus(1-6) raised the question of whether the plume emerges from a subsurface liquid source(6-8) or from the decomposition of ice(9-12). Previous compositional analyses of particles injected by the plume into Saturn's diffuse E ring have already indicated the presence of liquid water(8), but the mechanisms driving the plume emission are still debated(13). Here we report an analysis of the composition of freshly ejected particles close to the sources. Salt-rich ice particles are found to dominate the total mass flux of ejected solids (more than 99 per cent) but they are depleted in the population escaping into Saturn's E ring. Ice grains containing organic compounds are found to be more abundant in dense parts of the plume. Whereas previous Cassini observations were compatible with a variety of plume formation mechanisms, these data eliminate or severely constrain non-liquid models and strongly imply that a salt-water reservoir with a large evaporating surface(7,8) provides nearly all of the matter in the plume.}, language = {en} } @article{SramaKruegerYamaguchietal.2012, author = {Srama, Ralf and Krueger, H. and Yamaguchi, T. and Stephan, T. and Burchell, M. and Kearsley, A. T. and Sterken, V. and Postberg, F. and Kempf, S. and Gr{\"u}n, Eberhard and Altobelli, Nicolas and Ehrenfreund, P. and Dikarev, V. and Horanyi, M. and Sternovsky, Zoltan and Carpenter, J. D. and Westphal, A. and Gainsforth, Z. and Krabbe, A. and Agarwal, Jessica and Yano, H. and Blum, J. and Henkel, H. and Hillier, J. and Hoppe, P. and Trieloff, M. and Hsu, S. and Mocker, A. and Fiege, K. and Green, S. F. and Bischoff, A. and Esposito, F. and Laufer, R. and Hyde, T. W. and Herdrich, G. and Fasoulas, S. and Jaeckel, A. and Jones, G. and Jenniskens, P. and Khalisi, E. and Moragas-Klostermeyer, Georg and Spahn, Frank and Keller, H. U. and Frisch, P. and Levasseur-Regourd, A. C. and Pailer, N. and Altwegg, K. and Engrand, C. and Auer, S. and Silen, J. and Sasaki, S. and Kobayashi, M. and Schmidt, J. and Kissel, J. and Marty, B. and Michel, P. and Palumbo, P. and Vaisberg, O. and Baggaley, J. and Rotundi, A. and Roeser, H. P.}, title = {SARIM PLUS-sample return of comet 67P/CG and of interstellar matter}, series = {EXPERIMENTAL ASTRONOMY}, volume = {33}, journal = {EXPERIMENTAL ASTRONOMY}, number = {2-3}, publisher = {SPRINGER}, address = {DORDRECHT}, issn = {0922-6435}, doi = {10.1007/s10686-011-9285-7}, pages = {723 -- 751}, year = {2012}, abstract = {The Stardust mission returned cometary, interplanetary and (probably) interstellar dust in 2006 to Earth that have been analysed in Earth laboratories worldwide. Results of this mission have changed our view and knowledge on the early solar nebula. The Rosetta mission is on its way to land on comet 67P/Churyumov-Gerasimenko and will investigate for the first time in great detail the comet nucleus and its environment starting in 2014. Additional astronomy and planetary space missions will further contribute to our understanding of dust generation, evolution and destruction in interstellar and interplanetary space and provide constraints on solar system formation and processes that led to the origin of life on Earth. One of these missions, SARIM-PLUS, will provide a unique perspective by measuring interplanetary and interstellar dust with high accuracy and sensitivity in our inner solar system between 1 and 2 AU. SARIM-PLUS employs latest in-situ techniques for a full characterisation of individual micrometeoroids (flux, mass, charge, trajectory, composition()) and collects and returns these samples to Earth for a detailed analysis. The opportunity to visit again the target comet of the Rosetta mission 67P/Churyumov-Gerasimeenternko, and to investigate its dusty environment six years after Rosetta with complementary methods is unique and strongly enhances and supports the scientific exploration of this target and the entire Rosetta mission. Launch opportunities are in 2020 with a backup window starting early 2026. The comet encounter occurs in September 2021 and the reentry takes place in early 2024. An encounter speed of 6 km/s ensures comparable results to the Stardust mission.}, language = {en} }