Open Research Online The Open University’s repository of research publications and other research outputs The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling Journal Item How to cite: Ciarletti, Valérie; Clifford, Stephen; Plettemeyer, Dirk; LeGall, Alice; Hervé, Yann; Dorizon, Sophie; Quantin- Nataf, Cathy; Benedix, Wolf-Stefan; Schwenzer, Susanne; Pettinelli, Elena; Heggy, Essam; Herique, Alain; Berthellier, Jean-Jacques; Kofman, Wlodek; Vago, Jorge L.; Hamran, Svein-Erik and WISDOM team, . (2017). The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling. Astrobiology, 17(6-7) pp. 565–584. For guidance on citations see FAQs. c 2017 The Authors https://creativecommons.org/licenses/by-nc-nd/4.0/ Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.1089/ast.2016.1532 Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk ASTROBIOLOGY ExoMars Rover Mission Volume 17, Numbers 6 and 7, 2017 Mary Ann Liebert, Inc. DOI: 10.1089/ast.2016.1532 The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling Vale´rie Ciarletti,1 Stephen Clifford,2 Dirk Plettemeier,3 Alice Le Gall,1 Yann Herve´,1 Sophie Dorizon,1 Cathy Quantin-Nataf,4 Wolf-Stefan Benedix,3 Susanne Schwenzer,5 Elena Pettinelli,6 Essam Heggy,7 Alain Herique,8 Jean-Jacques Berthelier,1 Wlodek Kofman,8,11 Jorge L. Vago,9 Svein-Erik Hamran,10 and the WISDOM Team Abstract The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide infor- mation about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover’s 2-m drill. WISDOM will helpensurethesafety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples. Key Words: Ground penetrating radar—Martian shallow subsurface— ExoMars. Astrobiology 17, 565–584. 1. Introduction (<5 m) remain largely unknown. Until now, our insights have been limited to the stratigraphy exposed in outcrops and crater he search for evidence of life on Mars is the principal walls and the composition of samples acquired within *1to Tobjective of the 2020 European Space Agency (ESA, 10 cm of the surface (e.g., Grotzinger et al., 2005, 2015; Va- 2013)–Roscosmos ExoMars Rover mission. If such evidence is niman et al., 2014; Freissinet et al., 2015). For this reason, the to be found, it will most likely be in the subsurface, where ExoMars Rover mission has been optimized to investigate the organic molecules are shielded from the destructive effects of subsurface to identify, understand, and sample those locations ionizing radiation and atmospheric oxidants. Despite the enor- where evidence of past life is most likely to be found. mous volume of data acquired by previous orbital and landed To fulfill its objectives, the ExoMars Rover will be missions, the nature and structure of the shallow subsurface equipped with a variety of instruments dedicated to the study 1LATMOS/IPSL, UVSQ Universite´ Paris-Saclay, UPMC, Paris 06, CNRS, Guyancourt, France. 2Lunar and Planetary Institute, Houston, Texas. 3Technische Universitat Dresden, Dresden, Germany. 4Laboratoire de Ge´ologie de Lyon, Universite´ Claude Bernard Lyon 1/CNRS/ENS Lyon, Villeurbanne, France. 5Open University Centre for Earth Planetary Space and Astronomical Research, Milton Keynes, Milton Keynes, United Kingdom. 6Universita degli Studi Roma Tre Dipartimento di Matematica e Fisica, Roma, Italy. Downloaded by Open Univ Milton Keyes UK Lib/SWETS/40638182 from online.liebertpub.com at 07/28/17. For personal use only. 7University of Southern California Viterbi School of Engineering, Los Angeles, California. 8Universite´ Grenoble Alpes, IPAG, F-38000 Grenoble; CNRS, IPAG, F-38000, Grenoble, France. 9European Space Agency, ESA/ESTEC (HME-ME), Noordwijk, The Netherlands. 10Forsvarets forskningsinstitutt, Kjeller, Norway. 11Space Research Centre, PAN, Warsaw, Poland. ª Vale´rie Ciarletti et al., 2017; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. 565 566 CIARLETTI ET AL. and characterization of the planet’s surface and shallow tested by a French–German consortium supported by the subsurface (Vago et al., 2017). These investigations will French Space Agency Centre National d’Etudes Spatiales help identify the best locations for collecting samples with (CNES) and the German Space Agency Deutsche For- the rover’s 2-m drill, which will then be analyzed by a suite schungsanstalt fu¨r Luft-Und Raumfahrt (DLR) led by Vale´rie of onboard analytical instruments. The most fundamental Ciarletti (Principal Investigator) from LATMOS (Laboratoire requirement for the geologic characterization of the ExoMars Atmosphe`res, Milieux, Observations Spatiales) in Guyan- landing site will be to understand its nature and structure, court, France. LATMOS, in collaboration with Laboratoire which will provide invaluable insights into its origin and d’Astrophysique de Bordeaux (LAB), is responsible for the evolution. electronics unit (EU) hardware manufacturing and delivery, The Water Ice Subsurface Deposit Observation on Mars while the Technische Universita¨t Dresden (TUD, Germany) (WISDOM) radar has been selected as part of the ExoMars is responsible for the antenna system, under the supervision Rover mission Pasteur payload (Vago et al., 2017). It has of Dirk Plettemeier (Coprincipal Investigator). been designed to provide information about the nature of The WISDOM team consists of scientists from Europe the shallow subsurface over a depth range (*3–10 m, de- (France, Germany, Italy, Norway, Austria, and United pending on the dielectric properties of the regolith) that is Kingdom) and the United States, who have a broad range of both accessible and relevant to the search for traces of life. It expertise in martian geology, geomorphology, hydrology, will address some of the most important science questions mineralogy, signal and image processing, electromagnetic about the nature of the landing site, such as its depositional (EM) modeling, and 3D visualization, which represents the and erosional history, deformational and structural develop- best combination of skills necessary to analyze and interpret ment, and the potential role (and distribution) of liquid water the WISDOM data. The team is led by the Principal In- and ice in the evolution of the local landscape. In combina- vestigator, with the assistance of the Deputy Science Team tion with Pasteur payload’s other instruments that will be Leader, Stephen Clifford, from the Lunar and Planetary used in the area survey, WISDOM will help understand the Institute (LPI) in Houston, TX. To prepare for analysis of three-dimensional (3D) geological context so that the science the ExoMars radar data, the team has conducted (1) field team can assess the scientific interest of locations investigated tests with a WISDOM prototype in various martian ana- by the rover and choose the best site and depth at which to logue environments, (2) dielectric characterization of ana- collect samples. In addition, WISDOM will detect potential logue samples in the laboratory, and (3) numerical modeling buried hazards that might jeopardize drilling activities. of EM wave propagation in the subsurface, which takes into This article presents the WISDOM scientific objectives, a account the characteristics of the martian environment, as description of the instrument, and its expected performances well as WISDOM operational and instrumental characteris- in relevant environments. A section is also dedicated to the tics. These activities are essential to ensure the accurate in- measurement scenario and the data products that will be terpretation of WISDOM data that will eventually be returned delivered during the mission. Last, examples of both simu- from Mars. lated data and experimental data, acquired by a prototype that is representative of the WISDOM flight model, are 2. Science objectives shown to illustrate how WISDOM can contribute to the 2.1. The ExoMars mission’s science objectives success