Dr. Alexander Edouard Thelen

Dr. Alexander Edouard Thelen

  • Postdoctoral Fellow
  • 301.286.8797
  • NASA/GSFC
  • Mail Code: 693
  • Greenbelt , MD 20771
  • Employer: CATHOLIC UNIV OF AMERICA
  • Brief Bio

    Dr. Alexander ("Xander") Thelen is a Research Associate at the Catholic University of America Department of Physics, contracting for the NASA Goddard Space Flight Center astrochemistry lab. 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 and the development of interplanetary CubeSats.

    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 may be important for astrobiology studies of Titan.

    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) 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 Fellow

    NASA GSFC/NAI, 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 - 2018

    Awards

    ALMA Student Observing Support Award

     

    Grants

    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
    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

    Publications

    Refereed

    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." AJ, 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

    How Scientists Are Searching for Life on Titan

    7 / 15 / 2019

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

    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 Research Associate at the Catholic University of America Department of Physics, contracting for the NASA Goddard Space Flight Center astrochemistry lab. 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 and the development of interplanetary CubeSats.

    Publications

    Refereed

    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." AJ 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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