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Dr. Alexander Edouard Thelen

Photo of ALEXANDER THELEN

Dr. Alexander Edouard Thelen

  • Postdoctoral Fellow
  • 301.286.8797
  • NASA/GSFC
  • Mail Code: 693
  • Greenbelt , MD 20771
  • Employer: CALIFORNIA INSTITUTE OF TECHNOLOGY

    • Brief Bio

    Dr. Alexander ("Xander") Thelen is a NASA Astrobiology Postdoctoral Program fellow associated with the NASA Goddard Space Flight Center Planetary Systems Laboratory. Dr. Thelen's research pertains to the chemical composition and dynamics of planetary atmospheres; in particular, Dr. Thelen's work is focused on Titan and other outer solar system moons. Using high spatial and spectral resolution data from the Atacama Large Millimeter/submillimeter Array (ALMA), Dr. Thelen has begun investigating seasonal variations in Titan's atmospheric composition to continue the legacy of the Cassini-Huygens mission. Additionally, Dr. Thelen is interested in the study of other solar system objects using ALMA, the development of interplanetary CubeSats, and the investigation of Ocean World analogues.

    Research Interests

    Chemical Composition and Dynamics of Titan's Atmosphere

    The study of Titan's atmospheric composition through spatially resolved observations using the ALMA interferometer. Submillimeter spectra are modeled using the Non-linear optiMal Estimator for Multi-variatE spectral analySIS (NEMESIS) radiative transfer code to determine the vertical and latitudinal distribution of Titan's trace atmospheric constituents - many of which are hydrocarbon (CxHy) and nitrile (CxHy[CN]z) species. These results will allow us to understand how Titan's atmosphere responds to seasonal changes during the moon's northern summer, after the end of the Cassini-Huygens mission. Additionally, the distribution of trace atmospheric species, and the search for previously undetected species, may be important for astrobiology studies of Titan.

    Submillimeter Investigation of Planetary Atmospheres

    The investigation of other planetary atmospheres, including Mars, Neptune, and Jupiter, using techniques developed for studying Titan with ALMA. Through the wide range of chemical species observable in the submillimeter – including CO, hydrocarbons, and nitriles – measurements of chemical abundance, temperature, and atmospheric winds can be derived. With the newest generation of ground-based facilities such as ALMA, observations can be made with high spatial resolution allowing for unprecedented studies of atmospheric dynamics and composition from the ground.  

    Europa CubeSats

    Previous work involved a concept study of a Europa CubeSat to ride along with the Europa Clipper spacecraft. The Deployable Atmospheric Reconnaissance CubeSat with Sputtering Ion Detector at Europa (DARCSIDE) mission concept was developed at New Mexico State University in cooperation with JPL. The spacecraft would utilize an accelerometer and solid state particle telescope to monitor the atmospheric drag imparted upon the CubeSat from Europa's tenuous atmosphere, and determine the heavy ion flux at the moon from Jupiter's magnetosphere. These results could help to elucidate the connection between the origin and composition of Europa's atmosphere, and the harsh Jovian radiation environment.

    Positions/Employment

    12/2019 - Present

    NPP Astrobiology Fellow

    NAI/USRA, NASA Goddard Space Flight Center, Greenbelt MD
    10/2018 - 12/2019

    Research Associate

    Catholic University of America/NASA GSFC, Washington, DC
    2015 - 2018

    NASA ASTAR/JGFP Graduate Fellow

    New Mexico State University, Las Cruces, NM

    Education

    Ph.D., Astronomy

    New Mexico State University

    2013-2018

    Dissertation: "The Chemical Composition and Dynamics of Titan's Atmosphere as Revealed by ALMA"

    Advisors: Dr. Nancy Chanover, Dr. Conor Nixon

    B.S., Physics (Astrophysics)

    University of California, Santa Cruz

    2008-2012

    Thesis: "The Kinematics of Andromeda's DIG Disk"

    Advisor: Dr. Puragra Guha Thakurta

    Professional Societies

    American Astronomical Society, 2012 - Present
    AAS/Division for Planetary Sciences, 2014 - Present
    American Geophysical Union, 2016 - Present

    Professional Service

    AGU Fall Meeting Planning Committee: 2021–2022

    Primary Convener: 'Phosphine in the Venusian Atmosphere: Observations and Implications', AGU 2020 Fall Meeting; 'Outer Planets and Beyond', AGU 2021 Fall Meeting; 'Outer Planets and Beyond', AGU 2022 Fall Meeting

    Convener: 'Asteroids, Meteoroids, and Moons: Inner Solar System Processes', AGU 2021 Fall Meeting

    Session Chair: DPS 2020, AGU Fall Meeting 2021

    Proposal Panelist/External Reviewer: NASA ROSES, CDAP, FINESST, Keck TAC

    Proposal Executive Secretary: NASA CDAP

    Manuscript Referee: Astrophysical Journal Letters, Planetary Science Journal, Acta Astronautica, Astronomy & Astrophysics

    Awards

    ALMA Student Observing Support Award

    2020 ALMA Ambassador

    2021 ALMA Ambassador

    Grants

    01/02/2020 - 01/02/2022 NASA Astrobiology Postdoctoral Program (NPP) Fellowship, NASA/NAI

    Submillimeter Observations of Titan's Atmosphere: Implications for Astrobiology

    06/07/2019 - 12/31/2019 FLaRe, NASA GSFC

    Global Measurements of the Atmospheric Temperatures on Mars Using ALMA, and the Comparison to Climate Models and Spacecraft Datasets

    ; 0.25 FTE
    09/01/2015 - 09/01/2018 NASA ASTAR/JGFP Fellowship, NASA/NMSU

    The Chemical History and Evolution of Titan's Atmosphere as Revealed by ALMA

    Grant Amount: $165,000

    Other Professional Information

    Articles and Press Releases:

    • "How Scientists Are Searching for Life on Titan" - July 15th, 2019

    NASA Astrobiology feature story.

    https://nai.nasa.gov/articles/2019/7/15/how-earth-based-scientists-are-searching-for-life-on-titan/

    • "How to Plan a Space Mission" - July 12th, 2020

    New Yorker article on the 2019 Planetary Science Summer Seminar:

    https://www.newyorker.com/tech/annals-of-technology/how-to-plan-a-space-mission?fbclid=IwAR3Fu6sm6pE5lWuiX9Mh8vzJOkyLNBLMqJHnmXlmZHMCwTs-qMXADstd-4M

    • "NASA Scientists Discover ‘Weird’ Molecule in Titan’s Atmosphere" - October 27th, 2020

    NASA article on the detection of c-C3H2 in the atmosphere of Titan using ALMA

    https://www.nasa.gov/feature/goddard/2020/nasa-scientists-discover-a-weird-molecule-in-titan-s-atmosphere/

    Special Experience

    Accepted Observing Proposals:

    Apache Point 3.5 m

    • Observations of Jupiter's Atmosphere at Visible Wavelengths [DIS] (PI: A. E. Thelen) - 2012, 2013

    Atacama Large Millimeter/submillimeter Array

    • Elucidating Titan's High-Altitude Nitrogen Chemistry [Main Array] (PI: M. A. Cordiner) - Cycle 7 2019
    • Mapping Trace Gases in Jupiter's Atmosphere [ACA, TP] (PI: A. E. Thelen) - Cycle 7 Supplemental Call 2020
    • An Investigation of Latitudinal Variations in Titan's Atmospheric CH4 [Main Array] (PI: A. E. Thelen) - Cycle 8 2021
    • Unlocking Titan's Atmospheric Chemistry with ALMA [Main Array] (PI: A. E. Thelen) - Cycle 8 2021
    • Blowing in the Wind: Temporal Variability of Titan's High-Altitude Circulation System [Main Array] (PI: M. A. Cordiner) - Cycle 8 2021
    • Titan's Atmospheric Asymmetry [Main Array] (PI: N. A. Teanby) - Cycle 8 2021

    Other Facilities:

    • Titan's stratospheric winds from disk-resolved occultation imaging - Gemini South 2022
    • Co-I: Gemini North, Keck

    International Astrobiology Summer School  - 2016

    Astrobiology Graduate Conference Proposal Writing Workshop - 2017

    JPL Planetary Science Summer School 

    Development of BRIDGE mission concept to interstellar objects or long-period comets - 2019

    GSFC Planetary Science Winter School

    Participation in flight instrument design study - 2020

    Field Experience

    Measurements and sample collection in Yellowstone National Park hot springs - 2019

    Publications

    Refereed

    Thelen, A. E., C. A. Nixon, R. G. Cosentino, et al. M. A. Cordiner, N. A. Teanby, C. E. Newman, P. G. Irwin, and S. B. Charnley. 2022. "Variability in Titan’s Mesospheric HCN and Temperature Structure as Observed by ALMA." The Planetary Science Journal, 3 (6): 146 [10.3847/psj/ac7050]

    Villanueva, G. L., M. Cordiner, P. G. Irwin, et al. I. de Pater, B. Butler, M. Gurwell, S. N. Milam, C. A. Nixon, S. H. Luszcz-Cook, C. F. Wilson, V. Kofman, G. Liuzzi, S. Faggi, T. J. Fauchez, M. Lippi, R. Cosentino, A. E. Thelen, A. Moullet, P. Hartogh, E. M. Molter, S. Charnley, G. N. Arney, A. M. Mandell, N. Biver, A. C. Vandaele, K. R. de Kleer, and R. Kopparapu. 2021. "No evidence of phosphine in the atmosphere of Venus from independent analyses." Nature Astronomy, 5 (7): 631-635 [10.1038/s41550-021-01422-z]

    MacKenzie, S. M., S. P. Birch, S. Hörst, et al. C. Sotin, E. Barth, J. M. Lora, M. G. Trainer, P. Corlies, M. J. Malaska, E. Sciamma-O’Brien, A. E. Thelen, E. Turtle, J. Radebaugh, J. Hanley, A. Solomonidou, C. Newman, L. Regoli, S. Rodriguez, B. Seignovert, A. G. Hayes, B. Journaux, J. Steckloff, D. Nna-Mvondo, T. Cornet, M. Y. Palmer, R. M. Lopes, S. Vinatier, R. Lorenz, C. Nixon, E. Czaplinski, J. W. Barnes, E. Sittler, and A. Coates. 2021. "Titan: Earth-like on the Outside, Ocean World on the Inside." The Planetary Science Journal, 2 (3): 112 [10.3847/psj/abf7c9]

    Parks, M. C., C. A. Nixon, G. L. Villanueva, et al. M. D. Smith, A. S. Khayat, A. E. Thelen, E. Villard, S. B. Charnley, and P. G. Irwin. 2021. "Observations of Mars with ALMA: potential for future constraints of global circulation models." Journal of Astronomical Telescopes, Instruments, and Systems, 7 (02): [10.1117/1.jatis.7.2.025001]

    Moore, K., S. Courville, S. Ferguson, et al. A. Schoenfeld, K. Llera, R. Agrawal, P. Buhler, D. Brack, K. Connour, E. Czaplinski, M. DeLuca, A. Deutsch, N. Hammond, D. Kuettel, A. Marusiak, S. Nerozzi, J. Stuart, J. Tarnas, A. Thelen, J. Castillo-Rogez, W. Smythe, D. Landau, K. Mitchell, and C. Budney. 2021. "Bridge to the stars: A mission concept to an interstellar object." Planetary and Space Science, 197: 105137 [10.1016/j.pss.2020.105137]

    Cordiner, M. A., E. Garcia-Berrios, R. G. Cosentino, et al. N. A. Teanby, C. E. Newman, C. A. Nixon, A. E. Thelen, and S. B. Charnley. 2020. "Detection of Dynamical Instability in Titan’s Thermospheric Jet." The Astrophysical Journal, 904 (1): L12 [10.3847/2041-8213/abc688]

    Thelen, A. E., M. A. Cordiner, C. A. Nixon, et al. V. Vuitton, Z. Kisiel, S. B. Charnley, M. Y. Palmer, N. A. Teanby, and P. G. Irwin. 2020. "Detection of CH3C3N in Titan’s Atmosphere." The Astrophysical Journal, 903 (1): L22 [10.3847/2041-8213/abc1e1]

    Nixon, C. A., A. E. Thelen, M. A. Cordiner, et al. Z. Kisiel, S. B. Charnley, E. M. Molter, J. Serigano, P. G. Irwin, N. A. Teanby, and Y.-J. Kuan. 2020. "Detection of Cyclopropenylidene on Titan with ALMA." The Astronomical Journal, 160: 205 [10.3847/1538-3881/abb679]

    Kisiel, Z., C. A. Nixon, M. A. Cordiner, A. E. Thelen, and S. B. Charnley. 2020. "Propionitrile in the two lowest excited vibrational states in the laboratory and on Titan." Journal of Molecular Spectroscopy, 372: 111324 [10.1016/j.jms.2020.111324]

    Cordiner, M. A., N. A. Teanby, C. A. Nixon, et al. V. Vuitton, A. E. Thelen, and S. B. Charnley. 2019. "ALMA Spectral Imaging of Titan Contemporaneous with Cassini's Grand Finale." The Astronomical Journal, 158 (2): 76 [10.3847/1538-3881/ab2d20]

    Thelen, A. E., C. A. Nixon, M. A. Cordiner, et al. S. B. Charnley, P. G. Irwin, and Z. Kisiel. 2019. "Measurement of CH3D on Titan at Submillimeter Wavelengths." The Astronomical Journal, 157 (6): 219 [10.3847/1538-3881/ab19bb]

    Thelen, A. E., C. Nixon, N. Chanover, et al. M. Cordiner, E. Molter, N. Teanby, P. Irwin, J. Serigano, and S. Charnley. 2019. "Abundance measurements of Titan’s stratospheric HCN, HC3N, C3H4, and CH3CN from ALMA observations." Icarus, 319: 417-432 [10.1016/j.icarus.2018.09.023]

    Thelen, A. E., C. Nixon, N. Chanover, et al. E. Molter, M. Cordiner, R. Achterberg, J. Serigano, P. Irwin, N. Teanby, and S. Charnley. 2018. "Spatial variations in Titan’s atmospheric temperature: ALMA and Cassini comparisons from 2012 to 2015." Icarus, 307: 380-390 [10.1016/j.icarus.2017.10.042]

    Teanby, N. A., M. A. Cordiner, C. A. Nixon, et al. P. G. Irwin, S. M. Hörst, M. Sylvestre, J. Serigano, A. E. Thelen, A. M. Richards, and S. B. Charnley. 2018. "The Origin of Titan’s External Oxygen: Further Constraints from ALMA Upper Limits on CS and CH2NH." The Astronomical Journal, 155 (6): 251 [10.3847/1538-3881/aac172]

    Thelen, A. E., N. J. Chanover, J. Murphy, K. Rankin, and S. Stochaj. 2017. "A Europa CubeSat Concept Study for Measuring Atmospheric Density and Heavy Ion Flux." Journal of Small Satellites, 6 (2): 591-607.

    Talks, Presentations and Posters

    Invited

    Investigating Titan's Atmospheric Chemistry with ALMA

     6 / 16 / 2022

    American Astronomical Society 240th/Laboratory Astrophysics Division Meeting

    Exploring Titan's Atmospheric Chemistry and Dynamics with ALMA

     2021

    Kapteyn Astronomical Institute Colloquium, University of Groningen

    The Search for New Molecular Species in the Atmosphere of Titan

     12 / 2 / 2020

    Astrochemistry Discussions online talk series.

    https://discussions.astrochem.net/videos

    ALMA Observations of Titan's Dynamic Atmosphere into the Post-Cassini Era

     7 / 15 / 2020

    Japanese Geophysical Union - American Geophysical Union Joint Virtual Meeting 2020

    Other

    Titan's Variable Mesospheric Thermal Structure as Measured by ALMA

     12 / 2020

    American Geophysical Union Fall Meeting

    Detection of CH3C3N in Titan's Atmosphere

     10 / 2020

    AAS/Division of Planetary Sciences 52nd Meeting

    The Temporal Variability of Titan’s Atmosphere During Northern Summer

     12 / 2019

    American Geophysical Union Fall Meeting

    Submillimeter Detection of CH3D on Titan

     9 / 2019

    AAS/Division of Planetary Sciences + EPSC Joint Meeting

    Titan's Atmospheric CH3D Measured in the Submillimeter with ALMA

     5 / 2019

    New Horizons in Planetary Systems

    Titan's Atmospheric Dynamics Revealed Through Temperature and Chemical Abundance Measurements from 2012-2015 ALMA Observations

     10 / 2018

    AAS/Division for Planetary Sciences 50th Meeting

    ALMA and Cassini Comparisons of Titan's Stratospheric Temperature from 2012-2015

     10 / 2017

    AAS/Division for Planetary Sciences 49th Meeting

    Measuring Spatial and Temporal Variations in Titan's Atmosphere with ALMA

     4 / 2017

    Titan Through Time 4

    Spatial Variations of Chemical Abundances in Titan's Atmosphere as Revealed by ALMA

     10 / 2016

    AAS/Division for Planetary Sciences 48th Meeting

    Brief Bio

    Dr. Alexander ("Xander") Thelen is a NASA Astrobiology Postdoctoral Program fellow associated with the NASA Goddard Space Flight Center Planetary Systems Laboratory. Dr. Thelen's research pertains to the chemical composition and dynamics of planetary atmospheres; in particular, Dr. Thelen's work is focused on Titan and other outer solar system moons. Using high spatial and spectral resolution data from the Atacama Large Millimeter/submillimeter Array (ALMA), Dr. Thelen has begun investigating seasonal variations in Titan's atmospheric composition to continue the legacy of the Cassini-Huygens mission. Additionally, Dr. Thelen is interested in the study of other solar system objects using ALMA, the development of interplanetary CubeSats, and the investigation of Ocean World analogues.

    Publications

    Refereed

    Thelen, A. E., C. A. Nixon, R. G. Cosentino, et al. M. A. Cordiner, N. A. Teanby, C. E. Newman, P. G. Irwin, and S. B. Charnley. 2022. "Variability in Titan’s Mesospheric HCN and Temperature Structure as Observed by ALMA." The Planetary Science Journal 3 (6): 146 [10.3847/psj/ac7050]

    Villanueva, G. L., M. Cordiner, P. G. Irwin, et al. I. de Pater, B. Butler, M. Gurwell, S. N. Milam, C. A. Nixon, S. H. Luszcz-Cook, C. F. Wilson, V. Kofman, G. Liuzzi, S. Faggi, T. J. Fauchez, M. Lippi, R. Cosentino, A. E. Thelen, A. Moullet, P. Hartogh, E. M. Molter, S. Charnley, G. N. Arney, A. M. Mandell, N. Biver, A. C. Vandaele, K. R. de Kleer, and R. Kopparapu. 2021. "No evidence of phosphine in the atmosphere of Venus from independent analyses." Nature Astronomy 5 (7): 631-635 [10.1038/s41550-021-01422-z]

    MacKenzie, S. M., S. P. Birch, S. Hörst, et al. C. Sotin, E. Barth, J. M. Lora, M. G. Trainer, P. Corlies, M. J. Malaska, E. Sciamma-O’Brien, A. E. Thelen, E. Turtle, J. Radebaugh, J. Hanley, A. Solomonidou, C. Newman, L. Regoli, S. Rodriguez, B. Seignovert, A. G. Hayes, B. Journaux, J. Steckloff, D. Nna-Mvondo, T. Cornet, M. Y. Palmer, R. M. Lopes, S. Vinatier, R. Lorenz, C. Nixon, E. Czaplinski, J. W. Barnes, E. Sittler, and A. Coates. 2021. "Titan: Earth-like on the Outside, Ocean World on the Inside." The Planetary Science Journal 2 (3): 112 [10.3847/psj/abf7c9]

    Parks, M. C., C. A. Nixon, G. L. Villanueva, et al. M. D. Smith, A. S. Khayat, A. E. Thelen, E. Villard, S. B. Charnley, and P. G. Irwin. 2021. "Observations of Mars with ALMA: potential for future constraints of global circulation models." Journal of Astronomical Telescopes, Instruments, and Systems 7 (02): [10.1117/1.jatis.7.2.025001]

    Moore, K., S. Courville, S. Ferguson, et al. A. Schoenfeld, K. Llera, R. Agrawal, P. Buhler, D. Brack, K. Connour, E. Czaplinski, M. DeLuca, A. Deutsch, N. Hammond, D. Kuettel, A. Marusiak, S. Nerozzi, J. Stuart, J. Tarnas, A. Thelen, J. Castillo-Rogez, W. Smythe, D. Landau, K. Mitchell, and C. Budney. 2021. "Bridge to the stars: A mission concept to an interstellar object." Planetary and Space Science 197 105137 [10.1016/j.pss.2020.105137]

    Cordiner, M. A., E. Garcia-Berrios, R. G. Cosentino, et al. N. A. Teanby, C. E. Newman, C. A. Nixon, A. E. Thelen, and S. B. Charnley. 2020. "Detection of Dynamical Instability in Titan’s Thermospheric Jet." The Astrophysical Journal 904 (1): L12 [10.3847/2041-8213/abc688]

    Thelen, A. E., M. A. Cordiner, C. A. Nixon, et al. V. Vuitton, Z. Kisiel, S. B. Charnley, M. Y. Palmer, N. A. Teanby, and P. G. Irwin. 2020. "Detection of CH3C3N in Titan’s Atmosphere." The Astrophysical Journal 903 (1): L22 [10.3847/2041-8213/abc1e1]

    Nixon, C. A., A. E. Thelen, M. A. Cordiner, et al. Z. Kisiel, S. B. Charnley, E. M. Molter, J. Serigano, P. G. Irwin, N. A. Teanby, and Y.-J. Kuan. 2020. "Detection of Cyclopropenylidene on Titan with ALMA." The Astronomical Journal 160 205 [10.3847/1538-3881/abb679]

    Kisiel, Z., C. A. Nixon, M. A. Cordiner, A. E. Thelen, and S. B. Charnley. 2020. "Propionitrile in the two lowest excited vibrational states in the laboratory and on Titan." Journal of Molecular Spectroscopy 372 111324 [10.1016/j.jms.2020.111324]

    Cordiner, M. A., N. A. Teanby, C. A. Nixon, et al. V. Vuitton, A. E. Thelen, and S. B. Charnley. 2019. "ALMA Spectral Imaging of Titan Contemporaneous with Cassini's Grand Finale." The Astronomical Journal 158 (2): 76 [10.3847/1538-3881/ab2d20]

    Thelen, A. E., C. A. Nixon, M. A. Cordiner, et al. S. B. Charnley, P. G. Irwin, and Z. Kisiel. 2019. "Measurement of CH3D on Titan at Submillimeter Wavelengths." The Astronomical Journal 157 (6): 219 [10.3847/1538-3881/ab19bb]

    Thelen, A. E., C. Nixon, N. Chanover, et al. M. Cordiner, E. Molter, N. Teanby, P. Irwin, J. Serigano, and S. Charnley. 2019. "Abundance measurements of Titan’s stratospheric HCN, HC3N, C3H4, and CH3CN from ALMA observations." Icarus 319 417-432 [10.1016/j.icarus.2018.09.023]

    Thelen, A. E., C. Nixon, N. Chanover, et al. E. Molter, M. Cordiner, R. Achterberg, J. Serigano, P. Irwin, N. Teanby, and S. Charnley. 2018. "Spatial variations in Titan’s atmospheric temperature: ALMA and Cassini comparisons from 2012 to 2015." Icarus 307 380-390 [10.1016/j.icarus.2017.10.042]

    Teanby, N. A., M. A. Cordiner, C. A. Nixon, et al. P. G. Irwin, S. M. Hörst, M. Sylvestre, J. Serigano, A. E. Thelen, A. M. Richards, and S. B. Charnley. 2018. "The Origin of Titan’s External Oxygen: Further Constraints from ALMA Upper Limits on CS and CH2NH." The Astronomical Journal 155 (6): 251 [10.3847/1538-3881/aac172]

    Thelen, A. E., N. J. Chanover, J. Murphy, K. Rankin, and S. Stochaj. 2017. "A Europa CubeSat Concept Study for Measuring Atmospheric Density and Heavy Ion Flux." Journal of Small Satellites 6 (2): 591-607

                                                                                                                                                                                            
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