In-situ-analysis of ice particles in the solar system: application, methods, instrument developement
Final Report Abstract
The comprehensive goal of these DFG projects was the chemical characterization of icy bodies in the solar system by the means of a novel method. Utilizing in situ mass spectrometry, ice particles ejected by these bodies into space can be analyzed if they collide with appropriate detectors at high speed. If the particles' origins are known, the composition and geochemistry of the parent body can also be characterized. This approach is particularly well suited to icy materials and complements absorption-spectroscopy. Within the framework of the proposed research program, the method of in situ mass spectrometry was applied and further developed. In our core project, mass spectra from dust grains in the Saturnian system and detected by the Cosmic Dust Analyser (CDA) onboard the Cassini spacecraft, were analysed and supported by a series of lab experiments with icy analogue materials. A critical ingredient for our success in interpreting the mass spectra from CDA, was our laser-based analog experiment were we could simulate the spectral signatures of different non-icy compound embedded in the ice grains detected at Saturn. The main focus was on analysis of ice grains emerging from Saturn’s cryovolcanically active ocean moon Enceladus. In collaboration with partners in Japan and France we inferred geochemical and geophysical properties of the moons subsurface ocean and its interplay with Enceladus’ hydrothermally active rocky core. In particular, we found evidence for a variety of organic materials including surprisingly complex compounds. Although no clear indication for biogenic processes was found, our results substantially increased the astrobiological potential of the moons subsurface ocean. Additionally, in collaboration with another DFG project, we found evidence for interstellar dust in the Saturnian system and could infer its elemental composition. A highlight of the Cassini mission was its so-called Grand Finale were the space craft dove through the small gap between the planets innermost rings and its upper atmosphere. With CDA our team had the opportunity to measure debris from the rings that were falling into Saturn’s atmosphere, the so-called ‚ring-rain’. With our collaborators at LASP we measured a surprisingly high flux of tiny grains and could also analyse their composition. A surprisingly high abundance of silicatic, rocky material is still one of the puzzles the Grand Finale left us with and that are matter of intense on-going research. In another project we aimed to develop and mature successor instruments of CDA to improve the compositional characterization of ice grains in the outer solar system. We took part in the maturation of the Surface Dust Analyser (SUDA) onboard the Europa Clipper mission that is going to investigate the ocean moon Europa in a similar way as CDA did at Enceladus. Furthermore, we took part in the development of a detector (ENIJA) optimized to analyse Enceladus plume material in a future mission with the goal to further constrain the habitability of the small moon. With collaborators in Europe and the USA we took part in ESA and NASA mission proposals with this instrument. Although the missions were not selected the design and maturation of ENIJA is an on-going project. Finally we took the first steps in developing an entirely new and extremely powerful detector for hypervelocity ice grains on the basis of an ‘Orbitrap’ ion trap with collaborators in Germany, France and the Czech republic. Our results about organic material emerging from Enceladus’ ocean published in 2018 and 2019 inspired countless reports in the media all over the world. Also our first ever compositional in situ analysis of contemporary interstellar dust crossing the solar system had a large echo in the international media in 2016, as did the CDA measurements during Cassini’s Grand Finale. Three major public articles written by F. Postberg in Germany (Spektrum der Wissenschaft, Sterne und Weltraum) as well as the US (Scientific American) helped to transfer our scientific results to a greater interested public community. Additionally following invitations to public observatories and planetariums, several public outreach presentations have been conducted every year.
Publications
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(2020) Analog Experiments for the Identification of Trace Biosignatures in Ice Grains from Extraterrestrial Ocean Worlds. Astrobiology 20 (2) 179–189
Klenner, Fabian; Postberg, Frank; Hillier, Jon; Khawaja, Nozair; Reviol, René; Stolz, Ferdinand; Cable, Morgan L.; Abel, Bernd; Nölle, Lenz
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(2015) High-temperature water-rock interactions and hydrothermal environments in the chondrite-like core of Enceladus. Nature Communications 6:8604
Sekine, Y., Shibuya, T., Postberg, F., Hsu, H.-W., Suzuki, K., Masaki, Y., Kuwatani, T., Mori, M., Hong, P.K., Yoshizaki, M, Tachibana, S., and Sirono, S.-I.
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(2016) Flux and composition of interstellar dust at Saturn from Cassini’s Cosmic Dust Analyzer. Science, Vol. 352, pp. 312-318
Altobelli N., Postberg F., Fiege K., Trieloff M., Kimura H., Sterken V. J., Hsu H.-W., Hillier J., Khawaja N., Moragas-Klostermeyer G., Blum J., Burton M., Srama R., Kempf S., Gruen E.
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(2017) Powering prolonged hydrothermal activity inside Enceladus. Nature Astronomy 1:841-847
Choblet, G., Tobie, G., Sotin, C., Behounkova, M., Cadek, O., Postberg, F., and Soucek, O.
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(2018) Explorer of Enceladus and Titan (E2T): Investigating ocean worlds’ evolution and habitability in the solar system. Planetary & Space Science, 155:73-90
Mitri, G., Postberg, F., Soderblom, J.M., Wurz, P., Tortora, P., Abel, B., Barnes, J.W., Berga, M., Carrasco, N., Coustenis, A., de Vera, J.P.P., D’Ottavio, A., Ferri, F., Hayes, A.G., Hayne, P.O., Hillier, J.K., Kempf, S., Lebreton, J.-P., Lorenz, R.D., Martelli, A., Orosei, R., Petropoulos, A.E., Reh, K., Schmidt, J., Sotin, C., Srama, R., Tobie, G., Vorburger, A., Vuitton, V., Wong, A., and Zannoni, M.
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(2018) Impact ionisation mass spectrometry of platinum-coated olivine and magnesitedominated cosmic dust analogues, Planetary and Space Science, Volume 156, p. 96-110
Hillier J. K., Sternovsky, Z., Kempf, S., Trieloff, M., Guglielmino, M., Postberg, F., Price M. C.
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(2018) In situ collection of dust grains falling from Saturn’s rings into its atmosphere. Science, Vol. 362, 6410
Hsu H. -W., Schmidt J., Kempf S., Postberg F, Moragas-Klostermeyer G., Sieß M. Hoffmann H., Burton M., Ye S. Y., Kurth W. S. Horànyi M., Khawaja N., Spahn F., Schirdesahn D., O’Donoghue J., Moore L., Cuzzi J., Jones G. H., Srama R.
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(2018) Macromolecular organic compounds from the depths of Enceladus. Nature, 558:564-568
Postberg, F., Khawaja, N., Abel, B., Choblet, G., Glein, C.R., Gudipati, M.S., Henderson, B.L., Hsu, H.-W., Kempf, S., Klenner, F., Moragas-Klostermeyer, G., Magee, B., Nölle, L., Perry, M., Reviol, R., Schmidt, J., Srama, R., Stolz, F., Tobie, G., Trieloff, M., and Waite, J.H.
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(2019) Analogue Spectra for Impact Ionization Mass Spectra of Water Ice Grains Obtained at Different Impact Speeds in Space. Rapid Commun Mass Spectrom
Klenner, F., Postberg, F., Hillier, J., Khawaja, N., Reviol, R., Srama, R., Abel, B., Stolz, F., and Kempf, S.
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(2019) Low-mass nitrogen-, oxygen-bearing and aromatic compounds in Enceladean ice grains. MNRAS Vol. 289, Issue 4
Khawaja N., Postberg F., Hillier J., Klenner F., Kempf S., Nölle L., Reviol R., Zou Z., Srama R.
