Professional Appointments

  • 2020-present   Postdoctoral Fellow, Jet Propulsion Laboratory, Caltech.

Education

  • 2020   Ph.D., Brown University, Earth, Environmental & Planetary Sciences.

    • Spatial and temporal variations in the chemistry and mineralogy of mafic lacustrine systems on Earth and Mars. Advisor: Ralph Milliken.

  • 2017   M.Sc., Brown University, Earth, Environmental & Planetary Sciences.

    • Spectroscopic analysis of iron cycling in a terrestrial ultramafic lake and its implications for martian sedimentary systems. Advisor: Ralph Milliken.

  • 2013   B.A., Columbia University, Earth Science.

    • Extractable organic molecules are an effective thermometer of both naturally and artificially heated fault rocks. Advisors: Pratigya Polissar & Heather Savage.

Research Grants

  • 2022-2025 Mars Science Laboratory Participating Scientist Program (MSL-PSP). Science PI. “Understanding Mg-sulfate distribution, hydration state, and crystallinity in Mt. Sharp.” ($300,000.)

  • 2022 Spontaneous Research and Technology Development Program, Jet Propulsion Laboratory. Co-I. “Novel reaction design to test martian weathering.” ($40,000.)

  • 2022 Data Science Working Group, Jet Propulsion Laboratory. Co-I. “Developing machine learning models to facilitate the untargeted identification and classification of organics in complex mixtures via tandem mass spectrometry.” ($50,000.)

  • 2020-2022 Strategic Research and Technology Development Program, Jet Propulsion Laboratory. Science PI. “Experimental constraints on groundwater driven redox gradients on Mars.” ($300,000.)

Awards and Fellowships

•2022 Seal of Excellence, European Commission Marie Sklodowska-Curie Actions (MSCA-2021-PF).

•2020 Dissertation Fellowship, Brown University.

• 2015, 2017 NASA Group Achievement Award, MSL Science and Operations Team.
2015-2018 Presidential Fellowship for 3 years full support, Brown University Graduate School.
• 2013 Walter C. Pitman III Award for excellence in thesis research and presentation, Columbia University.

Lab and Mission Experience

  • Participating Scientist, Mars Science Laboratory. 2022-present.

  • Origins and Habitability Laboratory, JPL. 2020-present.

  • Science Team Member, Mars Science Laboratory. 2016-2022.

  • Research Laboratory Technician, Gemological Institute of America, diamond color origin group. 2013-2015.

  • Research Assistant, Lamont-Doherty Earth Observatory. 2011-2013.​

Field Work and Short Courses

  • 2021 Revolutionizing Access to the Martian Surface, Keck Institute for Space Studies, Caltech. (10 day short course, invited.)

  • 2018 Agouron Institute Advanced Geobiology Field School, Caltech. Naukluft Mountains, Namibia, 12 days in the field.

  • 2016 Field component of Sedimentary Cycle of Earth and Mars course, Brown University. Guadalupe Mountains, TX, 5 days in the field. 

  • 2013 Research sample collection. Punchbowl Fault, San Gabriel Mountains, CA, 3 days in the field.

  • 2012 Geologic Mapping course, Columbia University. Catskill Mountains, NY, 12 days in the field.

  • 2011 Research sample collection. Champlain Thrust Fault, Adirondack Mountains, VT, 2 days in the field.

Selected first author presentations

(*denotes oral presentation)


  • 2022 R. Y. Sheppard, A. A. Fraeman, L. M. Barge, J. M. Weber, L. Rodriguez, E. Martinez. Laboratory sediment columns to explore habitability of the martian subsurface under different groundwater conditions. AbSciCon, Atlanta, GA.

  • 2022 R. Y. Sheppard*, A. A. Fraeman, L. M. Barge, J. M. Weber, L. Rodriguez, E. Martinez. Laboratory sediment column simulations of chemical and redox gradients in the martian groundwater environment. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2021 R. Y. Sheppard*, L. Barge, A. A. Fraeman, J. M. Weber, L. Rodriguez, E. Flores, E. Martinez. Laboratory sediment column simulations of chemical and redox gradients in the martian groundwater environment. American Geophysical Union Fall Meeting, New Orleans, LA. 

  • 2021 R. Y. Sheppard, R. E. Milliken, J. M. Russell, M. D. Dyar, E. C. Sklute, S. Bijaksana, M. Melles, & H. Vogel. Mineral and chemical changes in a 100 m long sediment core from Lake Towuti, Indonesia and implications for mafic lacustrine sediments in Gale crater, Mars. American Geophysical Union Fall Meeting, New Orleans, LA. 

  • 2021 R. Y.* Sheppard, R. E. Milliken, & K. M. Robertson. Presence of clay minerals can obscure spectral evidence of Mg sulfates: Implications for orbital observations of Mars. Lunar and Planetary Science Conference, The Woodlands, TX. 

  • 2020 R. Y. Sheppard, Milliken, R., & Robertson, K. M. Reflectance measurements of clays and sulfates under Mars-like temperature and relative humidity cycles and implications for clay-sulfate assemblages in Gale crater. Lunar and Planetary Science Conference, The Woodlands, TX. (Canceled due to COVID-19)

  • 2020 R. Y. Sheppard, Milliken, R., Russell, J., Dyar, M. D., Sklute, E. C., Bijaksana, S., Melles, M., & Vogel, H. Mineral and chemical changes in a 100 m long sediment core from Lake Towuti, Indonesia and implications for mafic lacustrine sediments in Gale crater, Mars. Lunar and Planetary Science Conference, The Woodlands, TX. (Canceled due to COVID-19)

  • 2020 R. Y. Sheppard* Lamont-Doherty Earth Observatory geochemistry colloquium.

  • 2019 R. Y. Sheppard*, Milliken, R., & Robertson, K. M. Cycling of hydrous minerals and implications for the martian hydrological cycle. American Geophysical Union Fall Meeting, San Francisco, CA.

  • 2019 R. Y. Sheppard, Milliken, R., Itoh, Y., & Parente, M. Mineral stratigraphy around Mt. Sharp suggests aqueous processes affected the entire mound: directions for upcoming rover observations from orbital data. Ninth International Conference on Mars, Pasadena, CA.

  • 2019 R. Y. Sheppard, Milliken, R., Itoh, Y., & Parente, M. Lateral continuity of mineralogical and morphological contacts around Mt. Sharp: linking upcoming rover observations and orbital data. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2018 R. Y. Sheppard*, Milliken, R., Itoh, Y., & Parente, M. Assessing Lateral Variations in the Mineralogical Stratigraphy of Mt. Sharp: Linking Rover and Orbital Observations. American Geophysical Union Fall Meeting, Washington, D.C.

  • 2018 R. Y. Sheppard*, Milliken, R., Russell, J., Vogel, H., Melles, M., & Bijaksana, S. Signatures of iron cycling in a terrestrial redox-stratified lake and implications for Gale Crater, Mars. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2017 R. Y. Sheppard, Milliken, R., & Russell, J. Tracking changes in iron mineralogy through time in a terrestrial analogue for Gale Crater. American Geophysical Union Fall Meeting, New Orleans, LA.

  • 2017 R. Y. Sheppard, Milliken, R., & Russell, J. Iron oxidation state and cycling in sediments of Lake Towuti, Indonesia and implications for chemistry and mineralogy of Martian mudstones. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2012 R. E. Sheppard, Polissar, P. J., & Savage, H. M. Rapid heating experiments demonstrate the usefulness of organic molecules as an earthquake thermometer. American Geophysical Union Fall Meeting, San Francisco, CA.

Invited colloquia and team meeting talks

  • 2022 R. Y. Sheppard, Research Colloquium, Astrobiology & Planetary Science, Georgia Tech, Atlanta, GA.

  • 2021 R. Y. Sheppard, Research Colloquium, EAPS, Purdue, West Lafayette, IN.

  • 2020 R. Y. Sheppard, Geoclub Seminar Series, Caltech, Pasadena, CA. 

  • 2020 R. Y. Sheppard, Research Colloquium, Jet Propulsion Laboratory, Pasadena, CA. (Canceled due to COVID-19)

  • 2020 R. Y. Sheppard, Geochemistry Colloquium, Lamont-Doherty Earth Observatory, Palisades, NY.

  • 2019 R. Y. Sheppard, Milliken, R., Itoh, Y., & Parente, M. Updated orbital view of mineral stratigraphy of Mount Sharp and implications for Curiosity’s traverse. Mars Science Laboratory team meeting, NASA Goddard, Greenbelt, MD.

  • 2018 R. Y. SheppardMilliken, R., & Russell, J. Sedimentation in Lake Towuti & martian planetary processes. Towuti Drilling Project team meeting, Makassar, Indonesia.

  • 2017 R. Y. Sheppard, Milliken, R., & Russell, J. Lake Towuti as an analogue for trends seen in Gale Crater, Mars. Towuti Drilling Project team meeting, Bandung, Indonesia.

  • 2016 R. Y. Sheppard, Milliken, R., & Russell, J. Terrestrial analogs for chemical trends in Gale Crater: Ultramafic lakes in Indonesia and Iceland. NASA Astrobiology Institute team meeting, Williamstown, MA.

Selected coauthored presentations

  • 2022 J. M. Weber, E. Martinez, R. Y. Sheppard, L. E. Rodriguez, L. M. Barge. Mars weathering experiments: development and use of continuous-flow packed bed for geologic exploration. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2022 H. T. Manelski, R. Y. Sheppard, A. A. Fraeman, J. R. Johnson, R. Wiens, N. Lanza, J. Frydenvang. Classification of ChemCam passive spectral targets in Gale crater. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2022 J. K. Ando, R. Y. Sheppard, A. A. Fraeman, V. Sun. Locations and multispectral features of distinct classes of diagenetic features within the Murray formation, Gale crater, Mars. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2022 W. Rapin, R. Y. Sheppard, G. Dromart, J. Schieber, B. Clark, L. Kah, D. Rubin, B. L. Ehlmann, S. Gupta, G. Caravaca, N. Mangold, E. Dehouck, S. Le Mouelic, O. Gasnault, J. V. Clark, A. Bryk, B. Dietrich, R. C. Wiens. The Curiosity rover is exploring a key sulfate-bearing orbital facies. Lunar and Planetary Science Conference, The Woodlands, TX.

  • 2022 J. M. Weber, L. E. Rodriguez, R. Y. Sheppard, E. Martinez, L. M. Barge. Understanding habitability and prebiotic chemistry with continuous-flow terrestrial analogs. Invited. AbSciCon, Atlanta, GA.

  • 2022 T. C. Marlin, J. M. Weber, R. Y. Sheppard, S. M. Perl, L. M. Barge. Chemical gardens as analogs for prebiotic chemistry on ocean worlds. AbSciCon, Atlanta, GA.

  • 2022 D. Valadez, E. Flores, E. Martinez, R. Y. Sheppard, R. P. Hodyss, J. M. Weber, J. Castillo, B. Henderson, L. M. Barge. Sorption of prebiotic organics on iron sulfide minerals in ocean world analog systems. AbSciCon, Atlanta, GA.

    2022 E. Martinez, E. Flores, D. Valadez, J. M. Weber, T. C. Marlin, R. Y. Sheppard, L. M. Barge. Organic acid adsorption onto iron (oxy)hydroxides under ocean world analog conditions. AbSciCon, Atlanta, GA.

    2021 T. F. Bristow, E.B. Rampe, R. Sheppard, R. Milliken. In situ mineralogy of a clay-sulfate transition in Gale crater. American Geophysical Union Fall Meeting, New Orleans, LA.

  • 2021 A. A. Fraeman, M. Hughes, C. Seeger, J. Ando†, S. Jacob, J. Johnson, R. Sheppard, R. Arvidson, M. Rice, J. Bell. Spectral properties of diagenetic features near the clay-sulfate transition in Mt. Sharp. American Geophysical Union Fall Meeting, New Orleans, LA.

  • 2021 S. N. Lamm, L. E. Rodriguez, R. Y. Sheppard, S. M. Perl, A. J. Celestian, L. M. Barge. Classification of iron (oxy)hydroxides and sulfides using mission-ready spectroscopic techniques and machine learning. Geological Society of America Annual Meeting, Portland, OR.

  • 2020 R. E. Milliken, J. P. Grotzinger, R. Sheppard, R. Wiens, R. Gellert, L. M. Thompson, A. Vasavada, T. Bristow, & N. Mangold. The chemistry and mineralogy of an ancient lacustrine sequence on Mars: observations, interpretations, and future prospects. Lunar and Planetary Science Conference, The Woodlands, TX. (Canceled due to COVID-19)

  • 2019 R. E. Milliken, J. P. Grotzinger, R. Wiens, R. Gellert, L. M. Thompson, R. Sheppard, A. Vasavada, T. Bristow, & N. Mangold. The chemistry and mineralogy of an ancient lacustrine sequence on Mars: lessons learned from integrating rover and orbiter datasets. Ninth International Conference on Mars, Pasadena, CA.

  • 2018 D. Morriss, C. B. Sanders, J. P. Grotzinger, J. Busch, L. F. Cury, P. Daoust, W. W. Fischer, B. Howes, D. S. Jones, R. Sheppard, L. L. Nelson, J. P. Pu, D. P. Quinn, J. Wilcots, & R. Swart. Cap Sequence Post-dating Marinoan Glacial Deposits, Naukluft Mountains, Namibia. American Geophysical Union Fall Meeting, Washington, D.C.

  • 2017 A. C. Pascuzzo, B. C. Johnson, R. Y. Sheppard, E. A. Fisher, & S. E. Wiggins. Porosity and salt content determine if subduction can occur in Europa’s ice shell. Europa Deep Dive 1: Ice-Shell Exchange Processes, Houston, TX.

  • 2015 H. Savage, P. J. Polissar, H. Rabinowitz, & R. Sheppard. Some like it hot: the spectrum of temperature rise during earthquakes. American Geophysical Union Fall Meeting, San Francisco, CA.

  • 2012 H. Savage, P. J. Polissar, R. Sheppard, C. Rowe, & J. Kirkpatrick. Organic geochemical evidence for frictional heating of the NE Japan decollement in drillcores from Expedition 343: JFAST. American Geophysical Union Fall Meeting, San Francisco, CA.

  • 2011 H. Savage, P. J. Polissar, R. Sheppard, E. Brodsky, & C. Rowe. Do faults stay cool under stress? American Geophysical Union Fall Meeting, San Francisco, CA.

  • 2011 P. J. Polissar, H. Savage, R. Sheppard, C. Rowe, & E. Brodsky. What’s Cooking? Evaluating frictional stress using extractable organic material in fault zones. American Geophysical Union Fall Meeting, San Francisco, CA.

Teaching

  • 2018 Instructor, summer course, Brown University's STEM II program. 

  • 2018 Teaching Assistant, Planetary Geology (GEOL0810), Brown University.

  • 2017 Teaching Assistant, summer course in Brown University’s STEM II program.

Mentoring

  • 2021 Undergraduate advisees hosted by Caltech/JPL: Henry Manelski, Jordan Ando.

  • 2016-2020 Undergraduate advisees hosted by Brown University: Ana Colon (now a PhD student at U. of Oregon), Christopher Yen (now a PhD student at WashU), Sarah Martinez, Grant Rutherford (now a PhD student at MIT), Catherine Miranda.

  • 2018 Leadership Alliance Program Mentor, Brown University’s Leadership Alliance Program. Led weekly meetings with interns focused on completing a NSF-GRFP-style research proposal, poster presentation, and oral presentation.

Other Service and Outreach

  • 2022 Session Convener, AbSciCon, “Diagenesis and Subsurface Habitable Environments.” (Scheduled.)

  • 2021 Reviewer, Graduate Women In Science (GWIS) National Fellowship Program.

  • 2020 Panelist, NASA review panel.

  • 2019 Session Convener and Chair, American Geophysical Union Fall Meeting, “Evidence of water- rock interaction throughout the Solar System,” oral and poster session.

  • 2019 Executive secretary, NASA review panel.

  • 2019 Workshop leader, Girl Scout Senior Leadership Conference, Salve Regina University. "Craters, spacecraft, and the surfaces of our Solar System."

  • 2018-present GeoW+ Co-Founder and Graduate Student Leader, Brown University. Intersectional mentoring and social group for the department's underrepresented race and gender undergraduates.

  • 2018-present Graduate Student DIAP Representative, Brown University. Faculty-selected member of the department’s Diversity and Inclusion Action Plan Committee, composed of faculty, graduate students, undergrads, and staff.

  • 2018-present Graduate Student Faculty Representative, Brown University. Student-elected liaison between faculty and graduate students. Attended most weekly faculty meetings.

  • 2018-2019 Graduate Student Climate Task Force Representative, Brown University. Student-elected member of the Department’s Planetary Climate Task Force.