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The Holy Grail: a Road Map for Unlocking the Climate Record Stored Within Mars' Polar Layered Deposits

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Journal Pre-proof The Holy Grail: A road map for unlocking the climate record stored within Mars' polar layered deposits Isaac B. Smith, Paul O. Hayne, Shane Byrne, Patricio Becerra, Melinda Kahre, Wendy Calvin, Christine Hvidberg, Sarah Milkovich, Peter Buhler, Margaret Landis, Briony Horgan, Armin Kleinböhl, Matthew R. Perry, Rachel Obbard, Jennifer Stern, Sylvain Piqueux, Nicolas Thomas, Kris Zacny, Lynn Carter, Lauren Edgar, Jeremy Emmett, Thomas Navarro, Jennifer Hanley, Michelle Koutnik, Nathaniel Putzig, Bryana L. Henderson, John W. Holt, Bethany Ehlmann, Sergio Parra, Daniel Lalich, Candice Hansen, Michael Hecht, Don Banfield, Ken Herkenhoff, David A. Paige, Mark Skidmore, Robert L. Staehle, Matthew Siegler PII: S0032-0633(19)30187-4 DOI: https://doi.org/10.1016/j.pss.2020.104841 Reference: PSS 104841 To appear in: Planetary and Space Science Received Date: 1 May 2019 Revised Date: 26 December 2019 Accepted Date: 9 January 2020 Please cite this article as: Smith, I.B., Hayne, P.O., Byrne, S., Becerra, P., Kahre, M., Calvin, W., Hvidberg, C., Milkovich, S., Buhler, P., Landis, M., Horgan, B., Kleinböhl, A., Perry, M.R., Obbard, R., Stern, J., Piqueux, S., Thomas, N., Zacny, K., Carter, L., Edgar, L., Emmett, J., Navarro, T., Hanley, J., Koutnik, M., Putzig, N., Henderson, B.L., Holt, J.W., Ehlmann, B., Parra, S., Lalich, D., Hansen, C., Hecht, M., Banfield, D., Herkenhoff, K., Paige, D.A., Skidmore, M., Staehle, R.L., Siegler, M., The Holy Grail: A road map for unlocking the climate record stored within Mars' polar layered deposits, Planetary and Space Science (2020), doi: https://doi.org/10.1016/j.pss.2020.104841. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd. 1 The Holy Grail: A Road Map for Unlocking the Climate 2 Record Stored within Mars' Polar Layered Deposits 3 4 Authors and Affiliations 5 Isaac B. Smith 6 York University, Toronto, Ontario, Canada, M3J 1P3 7 Planetary Science Institute, Lakewood, CO 80401 8 Paul O. Hayne 9 University of Colorado Boulder, Boulder, Colorado 80309 10 Shane Byrne 11 University of Arizona, Tucson, Arizona 85721 12 Patricio Becerra 13 Universität Bern, Bern, Switzerland 14 Melinda Kahre 15 NASA Ames Research Center, Moffett Field, California 94035 16 Wendy Calvin 17 University of Nevada, Reno, Reno, Nevada 89557 18 Christine Hvidberg 19 University of Copenhagen, Copenhagen, Denmark 20 Sarah Milkovich 21 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 22 Peter Buhler 23 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 24 Margaret Landis 25 University of Colorado Boulder, Boulder, Colorado 80309 26 Briony Horgan 27 Purdue University, West Lafayette, Indiana 47907 28 Armin Kleinböhl 29 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 30 Matthew R. Perry 31 Planetary Science Institute, Lakewood, CO 80401 32 Rachel Obbard 33 SETI Institute, Mountain View, California 94043 34 Jennifer Stern 35 NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 36 Sylvain Piqueux 37 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 38 Nicolas Thomas 39 Universität Bern, Bern, Switzerland 40 Kris Zacny 41 Honeybee Robotics, Pasadena, California 91103 42 Lynn Carter Page 1 of 126 43 University of Arizona, Tucson, Arizona 85721 44 Lauren Edgar 45 U.S. Geological Survey, Flagstaff, Arizona 86001 46 Jeremy Emmett 47 New Mexico State University, Las Cruces, New Mexico 88003 48 Thomas Navarro 49 McGill Space Institute, McGill University, Montréal, Québec, Canada 50 University of California, Los Angeles, Los Angeles, California 90095 51 Jennifer Hanley 52 Lowell Observatory, Flagstaff, Arizona 86001 53 Michelle Koutnik 54 University of Washington, Seattle, Washington 98195 55 Nathaniel Putzig 56 Planetary Science Institute, Lakewood, CO 80401 57 Bryana L. Henderson 58 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 59 John W. Holt 60 University of Arizona, Tucson, Arizona 85721 61 Bethany Ehlmann 62 California Institute of Technology, Pasadena, California 91125 63 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 64 Sergio Parra 65 California Institute of Technology, Pasadena, California 91125 66 Daniel Lalich 67 Cornell University, Ithaca, New York 14853 68 Candice Hansen 69 Planetary Science Institute, Tucson, Arizona 85719 70 Michael Hecht 71 Haystack Observatory, Westford, Massachusetts 01886 72 Don Banfield 73 Cornell University, Ithaca, New York 14853 74 Ken Herkenhoff 75 U.S. Geological Survey, Flagstaff, Arizona 86001 76 David A. Paige 77 University of California, Los Angeles, Los Angeles, California 90095 78 Mark Skidmore 79 Montana State University, Bozeman, Montana 59717 80 Robert L. Staehle 81 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 82 Matthew Siegler 83 Planetary Science Institute, Tucson, Arizona 85719 Page 2 of 126 84 0: Abstract 85 In its polar layered deposits (PLD), Mars possesses a record of its recent climate, 86 analogous to terrestrial ice sheets containing climate records on Earth. Each PLD is greater than 87 2 km thick and contains thousands of layers, each containing information on the climatic and 88 atmospheric state during its deposition, creating a climate archive. With detailed 89 measurements of layer composition, it may be possible to extract age, accumulation rates, 90 atmospheric conditions, and surface activity at the time of deposition, among other important 91 parameters; gaining the information would allow us to "read" the climate record. Because Mars 92 has fewer complicating factors than Earth (e.g. oceans, biology, and human-modified climate), 93 the planet offers a unique opportunity to study the history of a terrestrial planet’s climate, 94 which in turn can teach us about our own planet and the thousands of terrestrial exoplanets 95 waiting to be discovered. 96 During a two-part workshop, the Keck Institute for Space Studies (KISS) hosted 38 Mars 97 scientists and engineers who focused on determining the measurements needed to extract the 98 climate record contained in the PLD. The group converged on four fundamental questions that 99 must be answered with the goal of interpreting the climate record and finding its history based 100 on the climate drivers 101 102 1. What are present and past fluxes of volatiles, dust, and other materials into and out of 103 the polar regions? 104 2. How do orbital forcing and exchange with other reservoirs affect those fluxes? Page 3 of 126 105 3. What chemical and physical processes form and modify layers? 106 4. What is the timespan, completeness, and temporal resolution of the climate history 107 recorded in the PLD? 108 109 The group then proposed numerous measurements in order to answer these questions 110 and detailed a sequence of missions and architecture to complete the measurements. In all, 111 several missions are required, including an orbiter that can characterize the present climate and 112 volatile reservoirs; a static reconnaissance lander capable of characterizing near surface 113 atmospheric processes, annual accumulation, surface properties, and layer formation 114 mechanism in the upper 50 cm of the PLD; a network of SmallSat landers focused on 115 meteorology for ground truth of the low-altitude orbiter data; and finally, a second landed 116 platform to access ~500 m of layers to measure layer variability through time. This mission 117 architecture, with two landers, would meet the science goals and is designed to save costs 118 compared to a single very capable landed mission. The rationale for this plan is presented 119 below. 120 In this paper we discuss numerous aspects, including our motivation, background of 121 polar science, the climate science that drives polar layer formation, modeling of the 122 atmosphere and climate to create hypotheses for what the layers mean, and terrestrial analogs 123 to climatological studies. Finally, we present a list of measurements and missions required to 124 answer the four maJor questions and read the climate record. 125 1. Background Page 4 of 126 126 1.A Justification and Timeliness 127 From a scientific point of view, this is the opportune time to set the direction of future 128 exploration of the polar layered deposits (PLD). The Mars polar science community held a 129 conference in 2016 (Smith et al., 2018) and the Mars Amazonian Climate Workshop in 2018 130 (Diniega and Smith, this issue) that distilled and summarized many years of research performed 131 on the datasets of numerous missions. Further, the Mars Exploration Program Analysis Group 132 (MEPAG) recently completed an ice and climate study identifying the polar regions as high 133 priority destinations for future exploration (ICE-SAG 2019). Those reports outline mature 134 hypotheses and maJor themes for future work that cannot be addressed with current
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