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  • 1.
    Becker, Tracy M.
    et al.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Cunningham, Nathaniel
    Nebraska Wesleyan Univ, Lincoln, NE USA..
    Molyneux, Philippa
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Roth, Lorenz
    KTH Royal Inst Technol, Stockholm, Sweden..
    Feaga, Lori M.
    Univ Maryland, College Pk, MD USA..
    Retherford, Kurt D.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, San Antonio, TX 78249 USA..
    Landsman, Zoe A.
    Univ Cent Florida, Florida Space Inst, Orlando, FL USA..
    Peavler, Emma
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Calif Los Angeles, Los Angeles, CA USA..
    Elkins-Tanton, Linda T.
    Arizona State Univ, Tempe, AZ USA..
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    HST UV Observations of Asteroid (16) Psyche2020In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 1, no 3, article id 53Article in journal (Refereed)
    Abstract [en]

    The Main Belt Asteroid (16) Psyche is the target object of the NASA Discovery Mission Psyche. We observed the asteroid at ultraviolet (UV) wavelengths (170-310 nm) using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope during two separate observations. We report that the spectrum is very red in the UV, with a blue upturn shortward of similar to 200 nm. We find an absorption feature at 250 nm and a weaker absorption feature at 275 nm that may be attributed to a metal-oxide charge transfer band. We find that the red-sloped, relatively featureless spectrum of (16) Psyche is best matched with the reflectance spectrum of pure iron; however, our intimate mixture models show that small grains of iron may dominate the reflectance spectrum even if iron only comprises up to 10% of the material on the surface. We also stress that there is a limited database of reflectances for planetary surface analogs at UV wavelengths for comparison with the spectrum of (16) Psyche. The mid- and far-UV spectra (<240 nm) are markedly different for each of the four asteroids observed at these wavelengths so far, including ones in the same spectral class, indicating that UV observations of asteroids could be used to better understand differences in the composition and processing of the surfaces of these small bodies.

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  • 2.
    Biber, H.
    et al.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Broetzner, J.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Jaeggi, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Szabo, P. S.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria.;Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Pichler, J.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Cupak, C.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Voith, C.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Cserveny, B.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Nenning, A.
    TU Wien, Inst Chem Technol & Analyt, Getreidemarkt 9, A-1060 Vienna, Austria..
    Mutzke, A.
    Max Planck Inst Plasma Phys, Wendelsteinstr 1, D-17491 Greifswald, Germany..
    Moro, Marcos V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Mezger, K.
    Univ Bern, Inst Geol Sci, Baltzerstr 13, CH-3012 Bern, Switzerland..
    Galli, A.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Wurz, P.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Aumayr, F.
    TU Wien, Inst Appl Phys, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria..
    Sputtering Behavior of Rough, Polycrystalline Mercury Analogs2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 12, article id 271Article in journal (Refereed)
    Abstract [en]

    The solar wind continuously impacts on rocky bodies in space, eroding their surface, thereby contributing significantly to the exosphere formations. The BepiColombo mission to Mercury will investigate the Hermean exosphere, which makes an understanding of the precise formation processes crucial for evaluation of the acquired data. We therefore developed an experimental setup with two microbalances that allows us to compare the sputter behavior of deposited thin solid layers with that of real mineral samples in the form of pressed powder. In addition, this technique is used to study the angular distribution of the sputtered particles. Using 4 keV He+ and 2 keV Ar+ ions, the sputter behavior of pellets of the minerals enstatite (MgSiO3) and wollastonite (CaSiO3) is studied, because these minerals represent analogs for the surface of the planet Mercury or the Moon. Pellets of powdered enstatite show significantly lower sputter yields than thin amorphous enstatite films prepared by pulsed laser deposition. 3D simulations of sputtering based on surface topography data from atomic force microscopy show that the observed reduction can be explained by the much rougher pellet surface alone. We therefore conclude that sputter yields from amorphous thin films can be applied to surfaces of celestial bodies exposed to ion irradiation, provided the effects of surface roughness, as encountered in realistic materials in space, are adequately accounted for. This also implies that taking surface roughness into account is important for modeling of the interaction of the solar wind with the surface of Mercury.

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  • 3.
    Dreyer, Joshua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Perryman, Rebecca S.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA..
    Waite, Jack Hunter
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA..
    Identifying Shadowing Signatures of C Ring Ringlets and Plateaus in Cassini Data from Saturn's Ionosphere2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 7, article id 168Article in journal (Refereed)
    Abstract [en]

    For orbits 288 and 292 of Cassini's Grand Finale, clear dips (sharp and narrow decreases) are visible in the H-2(+) densities measured by the Ion and Neutral Mass Spectrometer (INMS). In 2017, the southern hemisphere of Saturn was shadowed by its rings and the substructures within. Tracing a path of the solar photons through the ring plane to Cassini's position, we can identify regions in the ionosphere that were shadowed by the individual ringlets and plateaus (with increased optical depths) of Saturn's C ring. The calculated shadowed altitudes along Cassini's trajectory line up well with the dips in the H-2(+) data when adjusting the latter based on a detected evolving shift in the INMS timestamps since 2013, illustrating the potential for verification of instrument timings. We can further estimate the mean optical depths of the ringlets/plateaus by comparing the dips to inbound H-2(+) densities. Our results agree well with values derived from stellar occultation measurements. No clear dips are visible for orbits 283 and 287, whose periapsides were at higher altitudes. This can be attributed to the much longer chemical lifetime of H2+ at these higher altitudes, which in turn can be further used to estimate a lower limit for the flow speed along Cassini's trajectory. The resulting estimate of similar to 0.3 km s(-1) at an altitude of similar to 3400 km is in line with prior suggestions. Finally, the ringlet and plateau shadows are not associated with obvious dips in the electron density, which is expected due to their comparatively long chemical (recombination) lifetime.

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  • 4.
    Dreyer, Joshua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Buchert, Stephan C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Waite, Jack Hunter
    Space Science and Engineering Division, Southwest Research Institute, San Antonio, USA .
    Constraining the Positive Ion Composition in Saturn's Lower Ionosphere with the Effective Recombination Coefficient2021In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 1, article id 39Article in journal (Refereed)
    Abstract [en]

    The present study combines Radio and Plasma Wave Science/Langmuir Probe and Ion and Neutral Mass Spectrometer data from Cassini's last four orbits into Saturn's lower ionosphere to constrain the effective recombination coefficient α300 from measured number densities and electron temperatures at a reference electron temperature of 300 K. Previous studies have shown an influx of ring material causes a state of electron depletion due to grain charging, which will subsequently affect the ionospheric chemistry. The requirement to take grain charging into account limits the derivation of α300 to upper limits. Assuming photochemical equilibrium and using an established method to calculate the electron production rate, we derive upper limits for α300 of ≲ 3 × 10−7 cm3 s−1 for altitudes below 2000 km. This suggests that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients like HCO+. An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate coefficients > 5 × 10−7 cm3 s−1 at an electron temperature of 300 K.

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    Dreyer_2021_Planet._Sci._J._2_39
  • 5.
    Fauchez, Thomas J. J.
    et al.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Univ Space Res Assoc, Goddard Earth Sci Technol & Res GESTAR, Columbia, MD 21046 USA.;NASA GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA..
    Turbet, Martin
    Univ Geneva, Observ Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland..
    Sergeev, Denis E. E.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Math, Exeter EX4 4QF, Devon, England..
    Mayne, Nathan J. J.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, Devon, England..
    Spiga, Aymeric
    Sorbonne Univ, Ecole Normale Super, Ecole Polytech, CNRS,Lab Meteorol Dynam LMD IPSL, Paris, France..
    Sohl, Linda
    NASA, Goddard Inst Space Studies, New York, NY 10025 USA.;Columbia Univ, Ctr Climate Syst Res, New York, NY USA..
    Saxena, Prabal
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;Univ Maryland, College Pk, MD 20742 USA..
    Deitrick, Russell
    Univ Bern, Ctr Space & Habitabil, Gesell Str 6, CH-3012 Bern, Switzerland..
    Gilli, Gabriella
    Inst Astrofis & Cincias Espao IA, Edificio Leste 2 piso, P-1349018 Lisbon, Portugal..
    Domagal-Goldman, Shawn D. D.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;NASA NExSS Virtual Planetary Lab, Seattle, WA USA..
    Forget, Francois
    Sorbonne Univ, Ecole Normale Super, Ecole Polytech, CNRS,Lab Meteorol Dynam LMD IPSL, Paris, France..
    Consentino, Richard
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Univ Maryland, College Pk, MD 20742 USA..
    Barnes, Rory
    NASA NExSS Virtual Planetary Lab, Seattle, WA USA.;Univ Washington, Dept Astron, Box 951580, Seattle, WA 98195 USA..
    Haqq-Misra, Jacob
    NASA NExSS Virtual Planetary Lab, Seattle, WA USA.;Blue Marble Space Inst Sci, Seattle, WA USA..
    Way, Michael J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. NASA GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA; NASA, Goddard Inst Space Studies, New York, NY 10025 USA.
    Wolf, Eric T. T.
    NASA GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;NASA NExSS Virtual Planetary Lab, Seattle, WA USA.;Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Olson, Stephanie
    Purdue Univ, Dept Earth Atmospher & Planetary Sci, W Lafayette, IN 47907 USA..
    Crouse, Jaime S. S.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;Southeastern Univ Res Assoc, Ctr Res & Explorat Space Sci & Technol 2, 1201 New York Ave NW, Washington, DC 20005 USA..
    Janin, Estelle
    UCL, Math & Phys Sci Fac, Nat Sci Dept, London, England..
    Bolmont, Emeline
    Univ Geneva, Observ Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland..
    Leconte, Jeremy
    Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, B18N,Allee Groffroy St Hilaire, F-33615 Pessac, France..
    Chaverot, Guillaume
    Univ Geneva, Observ Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland..
    Jaziri, Yassin
    Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, B18N,Allee Groffroy St Hilaire, F-33615 Pessac, France..
    Tsigaridis, Kostantinos
    NASA, Goddard Inst Space Studies, New York, NY 10025 USA.;Columbia Univ, Ctr Climate Syst Res, New York, NY USA..
    Yang, Jun
    Peking Univ, Sch Phys, Dept Atmospher & Ocean Sci, Beijing 100871, Peoples R China..
    Pidhorodetska, Daria
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Univ Calif Riverside, Dept Earth & Planetary Sci, Riverside, CA USA..
    Kopparapu, Ravi K. K.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Chen, Howard
    Northwestern Univ, Dept Earth & Planetary Sci, Evanston, IL 60202 USA.;Ctr Interdisciplinary Explorat & Res Astrophys, Evanston, IL 60202 USA. Met Off, FitzRoy Rd, Exeter EX1 3PB, Devon, England..
    Boutle, Ian A. A.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, Devon, England..
    Lefevre, Maxence
    Univ Oxford, Atmospher Ocean & Planetary Phys, Oxford, England..
    Charnay, Benjamin
    Univ Paris, Univ PSL, Sorbonne Univ, LESIA,Observ Paris,CNRS, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Burnett, Andy
    Knowinnovation, 7903 Seminole Blvd,Suite 2303, Seminole, FL 33772 USA..
    Cabra, John
    Knowinnovation, 7903 Seminole Blvd,Suite 2303, Seminole, FL 33772 USA..
    Bouldin, Najja
    Knowinnovation, 7903 Seminole Blvd,Suite 2303, Seminole, FL 33772 USA..
    TRAPPIST Habitable Atmosphere Intercomparison (THAI) Workshop Report2021In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 3, article id 106Article in journal (Refereed)
    Abstract [en]

    The era of atmospheric characterization of terrestrial exoplanets is just around the corner. Modeling prior to observations is crucial in order to predict the observational challenges and to prepare for the data interpretation. This paper presents the report of the TRAPPIST Habitable Atmosphere Intercomparison workshop (2020 September 14-16). A review of the climate models and parameterizations of the atmospheric processes on terrestrial exoplanets, model advancements, and limitations, as well as direction for future model development, was discussed. We hope that this report will be used as a roadmap for future numerical simulations of exoplanet atmospheres and maintaining strong connections to the astronomical community.

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  • 6.
    Fauchez, Thomas J.
    et al.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Univ Space Res Assoc USRA, Goddard Earth Sci Technol & Res GESTAR, Columbia, MD 21046 USA.;Amer Univ, Coll Arts & Sci, Washington, DC 20016 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA..
    Villanueva, Geronimo L.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Sergeev, Denis E.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Math, Exeter EX4 4QF, England..
    Turbet, Martin
    Univ Geneva, Observ Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland.;PSL Res Univ, Sorbonne Univ, Ecole Normale Super, Ecole Polytech,Lab Metrorol Dynam,IPSL,CNRS, F-75005 Paris, France..
    Boutle, Ian A.
    Met Off, FitzRoy Rd, Exeter EX1 3PB, England.;Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, England..
    Tsigaridis, Kostas
    Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA..
    Way, Michael J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA.
    Wolf, Eric T.
    NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Domagal-Goldman, Shawn D.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Forget, Francois
    PSL Res Univ, Sorbonne Univ, Ecole Normale Super, Ecole Polytech,Lab Metrorol Dynam,IPSL,CNRS, F-75005 Paris, France..
    Haqq-Misra, Jacob
    NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA.;Blue Marble Space Inst Sci, Seattle, WA 98104 USA..
    Kopparapu, Ravi K.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD 20771 USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Manners, James
    Met Off, FitzRoy Rd, Exeter EX1 3PB, England..
    Mayne, Nathan J.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, England..
    The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). III. Simulated Observables-the Return of the Spectrum2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 9, article id 213Article in journal (Refereed)
    Abstract [en]

    The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) is a community project that aims to quantify how differences in general circulation models (GCMs) could impact the climate prediction for TRAPPIST-1e and, subsequently, its atmospheric characterization in transit. Four GCMs have participated in THAI: ExoCAM, LMD-Generic, ROCKE-3D, and the UM. This paper, focused on the simulated observations, is the third part of a trilogy, following the analysis of two land planet scenarios (Part I) and two aquaplanet scenarios (Part II). Here we show a robust agreement between the simulated spectra and the number of transits estimated to detect the land planet atmospheres. For the cloudy aquaplanet ones, a 5 sigma detection of CO2 could be achieved in about 10 transits if the atmosphere contains at least 1 bar of CO2. That number can vary by 41%-56% depending on the GCM used to predict the terminator profiles, principally due to differences in the cloud deck altitude, with ExoCAM and LMD-G producing higher clouds than ROCKE-3D and UM. Therefore, for the first time, this work provides "GCM uncertainty error bars" of similar to 50% that need to be considered in future analyses of transmission spectra. We also analyzed the intertransit spectral variability. Its magnitude differs significantly between the GCMs, but its impact on the transmission spectra is within the measurement uncertainties. THAI has demonstrated the importance of model intercomparison for exoplanets and also paved the way for a larger project to develop an intercomparison meta-framework, namely, the Climates Using Interactive Suites of Intercomparisons Nested for Exoplanet Studies.

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  • 7.
    Lillis, Robert J.
    et al.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mitchell, David
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Montabone, Luca
    Space Sci Inst, Boulder, CO 80301 USA..
    Heavens, Nicholas
    Space Sci Inst, Boulder, CO 80301 USA..
    Harrison, Tanya
    Planet Fed Inc, Washington, DC 20005 USA..
    Stuurman, Cassie
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Guzewich, Scott
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    England, Scott
    Virginia Tech Univ, Blacksburg, VA 24061 USA..
    Withers, Paul
    Boston Univ, Boston, MA 02215 USA..
    Chaffin, Mike
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80301 USA..
    Curry, Shannon
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Ao, Chi
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Matousek, Steven
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Barba, Nathan
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Woolley, Ryan
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Smith, Isaac
    York Univ, Toronto, ON M3J 1P3, Canada..
    Osinski, Gordon R.
    Univ Western Ontario, London, ON N6A 5B7, Canada..
    Kleinboehl, Armin
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Tamppari, Leslie
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Mischna, Michael
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Kass, David
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Smith, Michael
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Wolff, Michael
    Space Sci Inst, Boulder, CO 80301 USA..
    Kahre, Melinda
    NASA Ames Res Ctr, Mountain View, CA 94035 USA..
    Spiga, Aymeric
    IPSL, Lab Meteorol Dynam, Paris, France..
    Forget, Francois
    IPSL, Lab Meteorol Dynam, Paris, France..
    Cantor, Bruce
    Malin Space Sci Syst, San Diego, CA 92121 USA..
    Deighan, Justin
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80301 USA..
    Brecht, Amanda
    Bougher, Stephen
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Fowler, Christopher M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Patzold, Martin
    Rhein Inst Umweltforsch, Abt Planetenforsch, Cologne, Germany..
    Peter, Kerstin
    Rhein Inst Umweltforsch, Abt Planetenforsch, Cologne, Germany..
    Tellmann, Silvia
    Rhein Inst Umweltforsch, Abt Planetenforsch, Cologne, Germany..
    Lester, Mark
    Univ Leicester, Sch Phys & Astron, Leicester, England..
    Sanchez-Cano, Beatriz
    Univ Leicester, Sch Phys & Astron, Leicester, England..
    Luhmann, Janet
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Leblanc, Francois
    IPSL, Lab Atmospheres, Observat Spatiales, Paris, France..
    Halekas, Jasper
    Univ Iowa, Iowa City, IA 52242 USA..
    Brain, David
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80301 USA..
    Fang, Xiaohua
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80301 USA..
    Espley, Jared
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Opgenoorth, Hermann
    Univ Umeå, Umeå, Sweden..
    Vaisberg, Oleg
    Space Res Inst, Moscow, Russia..
    Hinson, David
    SETI Inst, Mountain View, CA 94043 USA..
    Asmar, Sami
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Vander Hook, Joshua
    CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA..
    Karatekin, Ozgur
    Royal Belgian Observ, Uccle, Belgium..
    Barjatya, Aroh
    Embry Riddle Aeronaut Univ, Daytona Beach, FL 32114 USA..
    Tripathi, Abhishek
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    MOSAIC: A Satellite Constellation to Enable Groundbreaking Mars Climate System Science and Prepare for Human Exploration2021In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 5, article id 211Article in journal (Refereed)
    Abstract [en]

    The Martian climate system has been revealed to rival the complexity of Earth's. Over the last 20 yr, a fragmented and incomplete picture has emerged of its structure and variability; we remain largely ignorant of many of the physical processes driving matter and energy flow between and within Mars' diverse climate domains. Mars Orbiters for Surface, Atmosphere, and Ionosphere Connections (MOSAIC) is a constellation of ten platforms focused on understanding these climate connections, with orbits and instruments tailored to observe the Martian climate system from three complementary perspectives. First, low-circular near-polar Sun-synchronous orbits (a large mothership and three smallsats spaced in local time) enable vertical profiling of wind, aerosols, water, and temperature, as well as mapping of surface and subsurface ice. Second, elliptical orbits sampling all of Mars' plasma regions enable multipoint measurements necessary to understand mass/energy transport and ion-driven escape, also enabling, with the polar orbiters, dense radio occultation coverage. Last, longitudinally spaced areostationary orbits enable synoptic views of the lower atmosphere necessary to understand global and mesoscale dynamics, global views of the hydrogen and oxygen exospheres, and upstream measurements of space weather conditions. MOSAIC will characterize climate system variability diurnally and seasonally, on meso-, regional, and global scales, targeting the shallow subsurface all the way out to the solar wind, making many first-of-their-kind measurements. Importantly, these measurements will also prepare for human exploration and habitation of Mars by providing water resource prospecting, operational forecasting of dust and radiation hazards, and ionospheric communication/positioning disruptions.

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  • 8.
    Sergeev, Denis E.
    et al.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Math, Exeter EX4 4QF, England..
    Fauchez, Thomas J.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Univ Space Res Assoc USRA, Goddard Earth Sci Technol & Res GESTAR, Columbia, MD USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA..
    Turbet, Martin
    Univ Geneva, Observ Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland.;Sorbonne Univ, PSL Res Univ, Ecole Normale Super, Ecole Polytech,Lab Meteorol Dynam,IPSL,CNRS, F-75005 Paris, France..
    Boutle, Ian A.
    Met Off, FitzRoy Rd, Exeter EX1 3PB, England.;Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, England..
    Tsigaridis, Kostas
    Columbia Univ, Ctr Climate Syst Res, New York, NY USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA..
    Way, Michael J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA.;Uppsala Univ, Dept Phys & Astron, Theoret Astrophys, Uppsala, Sweden..
    Wolf, Eric T.
    NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Domagal-Goldman, Shawn D.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Forget, Francois
    Sorbonne Univ, PSL Res Univ, Ecole Normale Super, Ecole Polytech,Lab Meteorol Dynam,IPSL,CNRS, F-75005 Paris, France..
    Haqq-Misra, Jacob
    NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA.;Blue Marble Space Inst Sci, Seattle, WA USA..
    Kopparapu, Ravi K.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Lambert, F. Hugo
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Math, Exeter EX4 4QF, England..
    Manners, James
    Met Off, FitzRoy Rd, Exeter EX1 3PB, England..
    Mayne, Nathan J.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, England..
    The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). II. Moist Cases-The Two Waterworlds2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 9, article id 212Article in journal (Refereed)
    Abstract [en]

    To identify promising exoplanets for atmospheric characterization and to make the best use of observational data, a thorough understanding of their atmospheres is needed. Three-dimensional general circulation models (GCMs) are one of the most comprehensive tools available for this task and will be used to interpret observations of temperate rocky exoplanets. Due to parameterization choices made in GCMs, they can produce different results, even for the same planet. Employing four widely used exoplanetary GCMs-ExoCAM, LMD-G, ROCKE-3D, and the UM-we continue the TRAPPIST-1 Habitable Atmosphere Intercomparison by modeling aquaplanet climates of TRAPPIST-1e with a moist atmosphere dominated by either nitrogen or carbon dioxide. Although the GCMs disagree on the details of the simulated regimes, they all predict a temperate climate with neither of the two cases pushed out of the habitable state. Nevertheless, the intermodel spread in the global mean surface temperature is nonnegligible: 14 K and 24 K in the nitrogen- and carbon dioxide-dominated case, respectively. We find substantial intermodel differences in moist variables, with the smallest amount of clouds in LMD-Generic and the largest in ROCKE-3D. ExoCAM predicts the warmest climate for both cases and thus has the highest water vapor content and the largest amount and variability of cloud condensate. The UM tends to produce colder conditions, especially in the nitrogen-dominated case due to a strong negative cloud radiative effect on the day side of TRAPPIST-1e. Our study highlights various biases of GCMs and emphasizes the importance of not relying solely on one model to understand exoplanet climates.

  • 9.
    Turbet, Martin
    et al.
    Sorbonne Univ, PSL Res Univ, Ecole Normale Super, Ecole Polytech,Lab Meteorol Dynam,IPSL,CNRS, F-75005 Paris, France.;Univ Geneva, Observ Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland..
    Fauchez, Thomas J.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Univ Space Res Assoc USRA, Goddard Earth Sci Technol & Res GESTAR, Columbia, MD USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA..
    Sergeev, Denis E.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Math, Exeter EX4 4QF, England..
    Boutle, Ian A.
    Met Off, FitzRoy Rd, Exeter England, England.;Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, England..
    Tsigaridis, Kostas
    Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA..
    Way, Michael J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA.;Uppsala Univ, Dept Phys & Astron, Theoret Astrophys, Uppsala, Sweden..
    Wolf, Eric T.
    NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO 80303 USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Domagal-Goldman, Shawn D.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Forget, Francois
    Sorbonne Univ, PSL Res Univ, Ecole Normale Super, Ecole Polytech,Lab Meteorol Dynam,IPSL,CNRS, F-75005 Paris, France..
    Haqq-Misra, Jacob
    NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA.;Blue Marble Space Inst Sci, Seattle, WA 98104 USA..
    Kopparapu, Ravi K.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Greenbelt, MD USA.;NASA, NExSS Virtual Planetary Lab, Seattle, WA 98195 USA..
    Lambert, F. Hugo
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Math, Exeter EX4 4QF, England..
    Manners, James
    Met Off, FitzRoy Rd, Exeter England, England..
    Mayne, Nathan J.
    Univ Exeter, Coll Engn Math & Phys Sci, Dept Astrophys, Exeter EX4 4QL, England..
    Sohl, Linda
    Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA.;NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA..
    The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). I. Dry Cases-The Fellowship of the GCMs2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 9, article id 211Article in journal (Refereed)
    Abstract [en]

    With the commissioning of powerful, new-generation telescopes such as the James Webb Space Telescope (JWST) and the ground-based Extremely Large Telescopes, the first characterization of a high molecular weight atmosphere around a temperate rocky exoplanet is imminent. Atmospheric simulations and synthetic observables of target exoplanets are essential to prepare and interpret these observations. Here we report the results of the first part of the TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) project, which compares 3D numerical simulations performed with four state-of-the-art global climate models (ExoCAM, LMD-Generic, ROCKE-3D, Unified Model) for the potentially habitable target TRAPPIST-1e. In this first part, we present the results of dry atmospheric simulations. These simulations serve as a benchmark to test how radiative transfer, subgrid-scale mixing (dry turbulence and convection), and large-scale dynamics impact the climate of TRAPPIST-1e and consequently the transit spectroscopy signature as seen by JWST. To first order, the four models give results in good agreement. The intermodel spread in the global mean surface temperature amounts to 7 K (6 K) for the N-2-dominated (CO2-dominated) atmosphere. The radiative fluxes are also remarkably similar (intermodel variations less than 5%), from the surface (1 bar) up to atmospheric pressures similar to 5 mbar. Moderate differences between the models appear in the atmospheric circulation pattern (winds) and the (stratospheric) thermal structure. These differences arise between the models from (1) large-scale dynamics, because TRAPPIST-1e lies at the tipping point between two different circulation regimes (fast and Rhines rotators) in which the models can be alternatively trapped, and (2) parameterizations used in the upper atmosphere such as numerical damping.

  • 10.
    Vigren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dreyer, Joshua
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Empirical Photochemical Modeling of Saturn's Ionization Balance Including Grain Charging2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 2, article id 49Article in journal (Refereed)
    Abstract [en]

    We present a semianalytical photochemical model of Saturn's near-equatorial ionosphere and adapt it to two regions (similar to 2200 and similar to 1700 km above the 1 bar level) probed during the inbound portion of Cassini's orbit 292 (2017 September 9). The model uses as input the measured concentrations of molecular hydrogen, hydrogen ion species, and free electrons, as well as the measured electron temperature. The output includes upper limits, or constraints, on the mixing ratios of two families of molecules, on ion concentrations, and on the attachment rates of electrons and ions onto dust grains. The model suggests mixing ratios of the two molecular families that, particularly near similar to 1700 km, differ notably from what independent measurements by the Ion Neutral Mass Spectrometer suggest. Possibly connected to this, the model suggests an electron-depleted plasma with a level of electron depletion of around 50%. This is in qualitative agreement with interpretations of Radio Plasma Wave Science/Langmuir Probe measurements, but an additional conundrum arises in the fact that a coherent photochemical equilibrium scenario then relies on a dust component with typical grain radii smaller than 3 angstrom.

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  • 11.
    Vigren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marschall, R.
    Southwest Res Inst, Dept Space Studies, Boulder, CO USA..
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rubin, M.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P2021In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 4, article id 156Article in journal (Refereed)
    Abstract [en]

    A recent work aided by Rosetta in situ measurements set constraints on the dust-to-gas mass emission ratio and the size distribution of dust escaping the nucleus of comet 67P/Churyumov-Gerasimenko near perihelion. Here we use this information along with other observables/parameters as input into an analytical model aimed at estimating the number density of electrons attached to dust particles near the position of Rosetta. These theoretical estimates are compared to in situ measurements of the degree of ionization. The comparison proposes that Rosetta, while near perihelion, was typically not in electron-depleted regions of the inner coma of 67P. Our work suggests a typical level of electron depletion probably below 10% and possibly below 1%. In line with previous studies, we find, again with certain assumptions and other observables/parameters as input, that the observed negative spacecraft charging to a few tens of volts does not significantly impact the detection of charged dust grains, with a possible exception for grains with radii less than similar to 10 nm.

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  • 12.
    Way, Michael J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA.;NASA, GSFC Sellers Exoplanet Environm Collaborat, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Ernst, Richard E.
    Carleton Univ, Dept Earth Sci, Ottawa, ON K1S 5B6, Canada.;Tomsk State Univ, Fac Geol & Geog, Tomsk, Russia..
    Scargle, Jeffrey D.
    NASA, Ames Res Ctr, Moffett Field, MS USA..
    Large-scale Volcanism and the Heat Death of Terrestrial Worlds2022In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 4, article id 92Article in journal (Refereed)
    Abstract [en]

    Large-scale volcanism has played a critical role in the long-term habitability of Earth. Contrary to widely held belief, volcanism, rather than impactors, has had the greatest influence on and bears most of the responsibility for large-scale mass extinction events throughout Earth's history. We examine the timing of large igneous provinces (LIPs) throughout Earth's history to estimate the likelihood of nearly simultaneous events that could drive a planet into an extreme moist or runaway greenhouse, leading to the end of volatile cycling and causing the heat death of formerly temperate terrestrial worlds. In one approach, we make a conservative estimate of the rate at which sets of near-simultaneous LIPs (pairs, triplets, and quartets) occur in a random history statistically the same as Earth's. We find that LIPs closer in time than 0.1-1 million yr are likely; significantly, this is less than the time over which terrestrial LIP environmental effects are known to persist. In another approach, we assess the cumulative effects with simulated time series consisting of randomly occurring LIP events with realistic time profiles. Both approaches support the conjecture that environmental impacts of LIPs, while narrowly avoiding grave effects on the climate history of Earth, could have been responsible for the heat death of our sister world Venus.

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  • 13.
    Zhang, Z.
    et al.
    Imperial Coll London, Blackett Lab, London, England..
    Desai, R. T.
    Imperial Coll London, Blackett Lab, London, England.;Univ Warwick, Ctr Fus Space & Astrophys, Coventry, England..
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, F. L.
    ESA ESTEC, Noordwijk, Netherlands..
    Miyake, Y.
    Kobe Univ, Grad Sch Syst Informat, Kobe, Japan..
    Usui, H.
    Kobe Univ, Grad Sch Syst Informat, Kobe, Japan..
    Simulating Secondary Electron and Ion Emission from the Cassini Spacecraft in Saturn's Ionosphere2023In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 4, no 6, article id 105Article in journal (Refereed)
    Abstract [en]

    The Cassini spacecraft's Grand Finale flybys through Saturn's ionosphere provided unprecedented insight into the composition and dynamics of the gas giant's upper atmosphere and a novel and complex spacecraft-plasma interaction. In this article, we further study Cassini's interaction with Saturn's ionosphere using three-dimensional particle-in-cell simulations. We focus on how electrons and ions, emitted from spacecraft surfaces due to the high-velocity impact of atmospheric water molecules, could have affected the spacecraft potential and low-energy plasma measurements. The simulations show emitted electrons extend upstream along the magnetic field, and for sufficiently high emission rates, charge the spacecraft to positive potentials. The lack of accurate emission rates and characteristics, however, makes differentiation between the prominence of secondary electron emission and ionospheric charged dust populations, which induce similar charging effects, difficult for Cassini. These results provide further context for Cassini's final measurements and highlight the need for future laboratory studies to support high-velocity flyby missions through planetary and cometary ionospheres.

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