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Open AccessArticle

Liquid Water Detection under the South Polar Layered Deposits of Mars—A Probabilistic Inversion Approach

Dipartimento di Matematica e Fisica, Università Degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
Consiglio Nazionale delle Ricerche, Istituto per il Rilevamento Elettromagnetico dell’Ambiente, Via Diocleziano 328, 80124 Napoli, Italy
Istituto Nazionale di Astrofisica, Istituto di Radioastronomia, Via Piero Gobetti 101, 40129 Bologna, Italy
Istituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
Instituto Volcanológico de Canarias (INVOLCAN), INtech La Laguna, Calle Álvaro Martín Díaz nº1 Bajo, 38320 La Laguna, Tenerife, Canary Islands, Spain
Author to whom correspondence should be addressed.
Remote Sens. 2019, 11(20), 2445;
Received: 20 September 2019 / Revised: 13 October 2019 / Accepted: 18 October 2019 / Published: 21 October 2019
(This article belongs to the Special Issue Real-Time Radar Imaging and Sensing)
Liquid water was present on the surface of Mars in the distant past; part of that water is now in the ground in the form of permafrost and heat from the molten interior of the planet could cause it to melt at depth. MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) has surveyed the Martian subsurface for more than fifteen years in search for evidence of such water buried at depth. Radar detection of liquid water can be stated as an inverse electromagnetic scattering problem, starting from the echo intensity collected by the antenna. In principle, the electromagnetic problem can be modelled as a normal plane wave that propagates through a three-layered medium made of air, ice and basal material, with the final goal of determining the dielectric permittivity of the basal material. In practice, however, two fundamental aspects make the inversion procedure of this apparent simple model rather challenging: (i) the impossibility to use the absolute value of the echo intensity in the inversion procedure; (ii) the impossibility to use a deterministic approach to retrieve the basal permittivity. In this paper, these issues are faced by assuming a priori information on the ice electromagnetic properties and adopting an inversion probabilistic approach. All the aspects that can affect the estimation of the basal permittivity below the Martian South polar cap are discussed and how detection of the presence of basal liquid water was done is described. View Full-Text
Keywords: Mars; radar data; surface and subsurface properties; inverse problems Mars; radar data; surface and subsurface properties; inverse problems
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MDPI and ACS Style

Lauro, S.E.; Soldovieri, F.; Orosei, R.; Cicchetti, A.; Cartacci, M.; Mattei, E.; Cosciotti, B.; Di Paolo, F.; Noschese, R.; Pettinelli, E. Liquid Water Detection under the South Polar Layered Deposits of Mars—A Probabilistic Inversion Approach. Remote Sens. 2019, 11, 2445.

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