1
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Recursive Enhancement of Weak Subsurface Boundaries and Its Application to SHARAD Data. REMOTE SENSING 2022. [DOI: 10.3390/rs14061525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sedimentary layers are composed of alternately deposited compositions in different periods, reflecting the geological evolution history of a planet. Orbital radar can detect sedimentary layers, but the radargram is contaminated by varying background noise levels. Traditional denoising methods, such as median filter, have difficulty dealing with such kinds of noise. We propose a recursive signal enhancement scheme to identify weak reflections from intense background noise. Numerical experiments with synthetic data and SHARAD radargrams illustrate that the proposed method can enhance the clarity of the radar echoes and reveal delicate sedimentary structures previously buried in the background noise. The denoising result presents better horizontal continuity and higher vertical resolution compared with those of the traditional methods.
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2
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SHARAD Observations of Temporal Variations of CO2 Ice Deposits at the South Pole of Mars. REMOTE SENSING 2022. [DOI: 10.3390/rs14030435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Mars’s polar regions are covered by kilometers-thick layered deposits which carry a record of the planet’s climate history. The deposition and volatilization of the shallow CO2 deposits in the south pole have a large impact on the planet’s atmosphere and environment. This research focuses on the timing variation of the thickness of the shallow deposits based on the SHARAD data collected from the past 11 terrestrial years, and analysis of the contributing factors based on the volatilization and deposition mechanisms of surface and subsurface materials. In this work, we selected more than four thousand data points, covering several seasons and Martian years, to extract radar echoes and calculate the thickness changes in the subsurface layer over time. We found that the thickness of the CO2 layer becomes thinner in the summer, with seasonal variation in the range of ~16–45 m. The thickness variations have a Gaussian-like distribution and do not increase with the distance between the compared node pair, implying that the phenomenon is not caused by regional differences. The overall thickness within the 11 terrestrial years does not show a clear trend of thickening or thinning, indicating a moderate vertical change of the southern deposits.
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3
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Frigeri A, Ercoli M. The ScanMars Subsurface Radar Sounding Experiment on AMADEE-18. ASTROBIOLOGY 2020; 20:1338-1352. [PMID: 33179967 DOI: 10.1089/ast.2019.2037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Terrestrial simulations for crewed missions are critically important for testing technologies and improving methods and procedures for future robotic and human planetary exploration. In February 2018, AMADEE-18 simulated a mission to Mars in the Dhofar region of Oman. During the mission, a field crew coordinated by the Österreichisches Weltraum Forum (OeWF) accomplished several experiments in the fields of astrobiology, space physiology and medicine, geology, and geophysics. Within the scientific payload of AMADEE-18, ScanMars provided geophysical radar imaging of the subsurface at the simulated landing site and was operated by analog astronauts wearing spacesuits during extra-vehicular activities. The analog astronauts were trained to operate a ground-penetrating radar instrument that transmits and then collects radio waves carrying information about the geological setting of the first few meters of the subsurface. The data presented in this work show signal returns from structures down to 4 m depth, associated with the geology of the investigated rocks. Integrating radar data and the analog astronauts' observations of the geology at the surface, it was possible to identify the contact between shallow sediments and bedrock, the local occurrence of conductive soils, and the presence of pebbly materials in the shallow subsurface, which together describe the geology of recent loose sediments overlying an older deformed bedrock. The results obtained by ScanMars confirm that subsurface radar sounding at martian landing sites is key for the geological characterization at shallow depths. The geologic model of the subsurface can be used as the basis for reconstructing palaeoenvironments and paleo-habitats, thus assisting scientific investigations looking for traces of present or past life on the Red Planet. Highlights The ScanMars experiment brings a ground-penetrating radar to the AMADEE-18 simulated Mars mission. The ScanMars radar was operated following procedures and training developed before the mission. Approximately 2000 m of radar data profiles have been acquired during the analog mission. Combining the results for ScanMars, orbital remote sensing data, and first-person observation in the field while wearing spacesuits (analog astronauts), it was possible to generate a geological model at the AMADEE-18 study site.
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Affiliation(s)
- Alessandro Frigeri
- Istituto di Astrofisica e Planetologia Spaziali (IAPS), Istituto Nazionale di Astrofisica (INAF), Rome, Italy
| | - Maurizio Ercoli
- Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, Perugia, Italy
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4
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Orosei R, Ding C, Fa W, Giannopoulos A, Hérique A, Kofman W, Lauro SE, Li C, Pettinelli E, Su Y, Xing S, Xu Y. The Global Search for Liquid Water on Mars from Orbit: Current and Future Perspectives. Life (Basel) 2020; 10:life10080120. [PMID: 32722008 PMCID: PMC7460233 DOI: 10.3390/life10080120] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 07/17/2020] [Accepted: 07/20/2020] [Indexed: 12/02/2022] Open
Abstract
Due to its significance in astrobiology, assessing the amount and state of liquid water present on Mars today has become one of the drivers of its exploration. Subglacial water was identified by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) aboard the European Space Agency spacecraft Mars Express through the analysis of echoes, coming from a depth of about 1.5 km, which were stronger than surface echoes. The cause of this anomalous characteristic is the high relative permittivity of water-bearing materials, resulting in a high reflection coefficient. A determining factor in the occurrence of such strong echoes is the low attenuation of the MARSIS radar pulse in cold water ice, the main constituent of the Martian polar caps. The present analysis clarifies that the conditions causing exceptionally strong subsurface echoes occur solely in the Martian polar caps, and that the detection of subsurface water under a predominantly rocky surface layer using radar sounding will require thorough electromagnetic modeling, complicated by the lack of knowledge of many subsurface physical parameters. Higher-frequency radar sounders such as SHARAD cannot penetrate deep enough to detect basal echoes over the thickest part of the polar caps. Alternative methods such as rover-borne Ground Penetrating Radar and time-domain electromagnetic sounding are not capable of providing global coverage. MARSIS observations over the Martian polar caps have been limited by the need to downlink data before on-board processing, but their number will increase in coming years. The Chinese mission to Mars that is to be launched in 2020, Tianwen-1, will carry a subsurface sounding radar operating at frequencies that are close to those of MARSIS, and the expected signal-to-noise ratio of subsurface detection will likely be sufficient for identifying anomalously bright subsurface reflectors. The search for subsurface water through radar sounding is thus far from being concluded.
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Affiliation(s)
- Roberto Orosei
- Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, Via Piero Gobetti 101, 40129 Bologna, Italy
- Correspondence:
| | - Chunyu Ding
- School of Atmosphere Sciences, Sun Yat-sen University, 2 Daxue Road, Xiangzhou District, Zhuhai City 519000, China;
| | - Wenzhe Fa
- Institute of Remote Sensing and Geographical Information System, School of Earth and Space Sciences, Peking University, Beijing 100871, China;
| | - Antonios Giannopoulos
- School of Engineering, The University of Edinburgh, Alexander Graham Bell Building, Thomas Bayes Road, Edinburgh EH9 3FG, UK;
| | - Alain Hérique
- Université Grenoble Alpes, CNRS, CNES, IPAG, 38000 Grenoble, France; (A.H.); (W.K.)
| | - Wlodek Kofman
- Université Grenoble Alpes, CNRS, CNES, IPAG, 38000 Grenoble, France; (A.H.); (W.K.)
- Centrum Badan Kosmicznych Polskiej Akademii Nauk (CBK PAN), Bartycka 18A, 00-716 Warsaw, Poland
| | - Sebastian E. Lauro
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy; (S.E.L.); (E.P.)
| | - Chunlai Li
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, China; (C.L.); (Y.S.)
- University of Chinese Academy of Sciences, No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Elena Pettinelli
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy; (S.E.L.); (E.P.)
| | - Yan Su
- Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, China; (C.L.); (Y.S.)
- University of Chinese Academy of Sciences, No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Shuguo Xing
- Piesat Information Technology Co., Ltd, Beijing 100195, China;
| | - Yi Xu
- State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macau;
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5
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Liquid Water Detection under the South Polar Layered Deposits of Mars—a Probabilistic Inversion Approach. REMOTE SENSING 2019. [DOI: 10.3390/rs11202445] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
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.
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6
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Orosei R, Lauro SE, Pettinelli E, Cicchetti A, Coradini M, Cosciotti B, Di Paolo F, Flamini E, Mattei E, Pajola M, Soldovieri F, Cartacci M, Cassenti F, Frigeri A, Giuppi S, Martufi R, Masdea A, Mitri G, Nenna C, Noschese R, Restano M, Seu R. Radar evidence of subglacial liquid water on Mars. Science 2018; 361:490-493. [PMID: 30045881 DOI: 10.1126/science.aar7268] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 06/20/2018] [Indexed: 11/02/2022]
Abstract
The presence of liquid water at the base of the martian polar caps has long been suspected but not observed. We surveyed the Planum Australe region using the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument, a low-frequency radar on the Mars Express spacecraft. Radar profiles collected between May 2012 and December 2015 contain evidence of liquid water trapped below the ice of the South Polar Layered Deposits. Anomalously bright subsurface reflections are evident within a well-defined, 20-kilometer-wide zone centered at 193°E, 81°S, which is surrounded by much less reflective areas. Quantitative analysis of the radar signals shows that this bright feature has high relative dielectric permittivity (>15), matching that of water-bearing materials. We interpret this feature as a stable body of liquid water on Mars.
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Affiliation(s)
- R Orosei
- Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, Via Piero Gobetti 101, 40129 Bologna, Italy.
| | - S E Lauro
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
| | - E Pettinelli
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
| | - A Cicchetti
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - M Coradini
- Agenzia Spaziale Italiana, Via del Politecnico, 00133 Roma, Italy
| | - B Cosciotti
- Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
| | - F Di Paolo
- Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, Via Piero Gobetti 101, 40129 Bologna, Italy
| | - E Flamini
- Agenzia Spaziale Italiana, Via del Politecnico, 00133 Roma, Italy
| | - E Mattei
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - M Pajola
- Osservatorio Astronomico di Padova, Istituto Nazionale di Astrofisica, Vicolo Osservatorio 5, 35122 Padova, Italy
| | - F Soldovieri
- Consiglio Nazionale delle Ricerche, Istituto per il Rilevamento Elettromagnetico dell'Ambiente, Via Diocleziano 328, 80124 Napoli, Italy
| | - M Cartacci
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - F Cassenti
- Dipartimento di Ingegneria dell'Informazione, Elettronica e Telecomunicazioni, Università degli Studi di Roma "La Sapienza," Via Eudossiana 18, 00184 Roma, Italy
| | - A Frigeri
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - S Giuppi
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - R Martufi
- Dipartimento di Ingegneria dell'Informazione, Elettronica e Telecomunicazioni, Università degli Studi di Roma "La Sapienza," Via Eudossiana 18, 00184 Roma, Italy
| | - A Masdea
- E.P. Elettronica Progetti, Via Traspontina 25, 00040 Ariccia (RM), Italy
| | - G Mitri
- International Research School of Planetary Sciences, Università degli Studi "Gabriele d'Annunzio," Viale Pindaro 42, 65127 Pescara (PE), Italy
| | - C Nenna
- Danfoss Drives, Romstrasse 2 - Via Roma 2, 39014 Burgstall - Postal (BZ), Italy
| | - R Noschese
- Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - M Restano
- Serco, c/o ESA Centre for Earth Observation, Largo Galileo Galilei 1, 00044 Frascati (RM), Italy
| | - R Seu
- Dipartimento di Ingegneria dell'Informazione, Elettronica e Telecomunicazioni, Università degli Studi di Roma "La Sapienza," Via Eudossiana 18, 00184 Roma, Italy
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7
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Putzig NE, Smith IB, Perry MR, Foss FJ, Campbell BA, Phillips RJ, Seu R. Three-dimensional radar imaging of structures and craters in the Martian polar caps. ICARUS 2018; 308:138-147. [PMID: 29749975 PMCID: PMC5937288 DOI: 10.1016/j.icarus.2017.09.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Over the last decade, observations acquired by the Shallow Radar (SHARAD) sounder on individual passes of the Mars Reconnaissance Orbiter have revealed the internal structure of the Martian polar caps and provided new insights into the formation of the icy layers within and their relationship to climate. However, a complete picture of the cap interiors has been hampered by interfering reflections from off-nadir surface features and signal losses associated with sloping structures and scattering. Foss et al. (2017) addressed these limitations by assembling three-dimensional data volumes of SHARAD observations from thousands of orbital passes over each polar region and applying geometric corrections simultaneously. The radar volumes provide unprecedented views of subsurface features, readily imaging structures previously inferred from time-intensive manual analysis of single-orbit data (e.g., trough-bounding surfaces, a buried chasma, and a basal unit in the north, massive carbon-dioxide ice deposits and discontinuous layered sequences in the south). Our new mapping of the carbon-dioxide deposits yields a volume of 16,500 km3, 11% larger than the prior estimate. In addition, the radar volumes newly reveal other structures, including what appear to be buried impact craters with no surface expression. Our first assessment of 21 apparent craters at the base of the north polar layered deposits suggests a Hesperian age for the substrate, consistent with that of the surrounding plains as determined from statistics of surface cratering rates. Planned mapping of similar features throughout both polar volumes may provide new constraints on the age of the icy layered deposits. The radar volumes also provide new topographic data between the highest latitudes observed by the Mars Orbiter Laser Altimeter and those observed by SHARAD. In general, mapping of features in these radar volumes is placing new constraints on the nature and evolution of the polar deposits and associated climate changes.
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Affiliation(s)
- Nathaniel E Putzig
- Planetary Science Institute, 1546 Cole Boulevard, Suite 120, Lakewood, CO 80401, USA
| | - Isaac B Smith
- Planetary Science Institute, 1546 Cole Boulevard, Suite 120, Lakewood, CO 80401, USA
| | - Matthew R Perry
- Planetary Science Institute, 1546 Cole Boulevard, Suite 120, Lakewood, CO 80401, USA
| | - Frederick J Foss
- Freestyle Analytical and Quantitative Services, LLC, 2210 Parkview Drive, Longmont, CO 80504, USA
| | - Bruce A Campbell
- Smithsonian Institution, MRC 315, Center for Earth and Planetary Studies, National Air and Space Museum, 4th and Independence Ave, SW, Washington, DC 20560, USA
| | - Roger J Phillips
- Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, MO 63130, USA
| | - Roberto Seu
- Sapienza University of Rome, DIET Department, Via Eudossiana, 18, 00184 Rome, ITALY
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8
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Foss FJ, Putzig NE, Campbell BA, Phillips RJ. 3-D Imaging of Mars' Polar Ice Caps Using Orbital Radar Data. ACTA ACUST UNITED AC 2018; 36:43-57. [PMID: 29400351 DOI: 10.1190/tle36010043.1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Since its arrival in early 2006, various instruments aboard NASA's Mars Reconnaissance Orbiter (MRO) have been collecting a variety of scientific and engineering data from orbit around Mars. Among these is the SHAllow RADar (SHARAD) instrument, supplied by Agenzia Spaziale Italiana (ASI) and designed for subsurface sounding in the 15-25 MHz frequency band. As of this writing, MRO has completed over 46,000 nearly polar orbits of Mars, 30% of which have included active SHARAD data collection. By 2009, a sufficient density of SHARAD coverage had been obtained over the polar regions to support 3-D processing and analysis of the data. Using tools and techniques commonly employed in terrestrial seismic data processing, we have processed subsets of the resulting collection of SHARAD observations covering the north and south polar regions as SHARAD 3-D volumes, imaging the interiors of the north and south polar ice caps known, respectively, as Planum Boreum and Planum Australe. After overcoming a series of challenges revealed during the 3-D processing and analysis, a completed Planum Boreum 3-D volume is currently being used for scientific research. Lessons learned in the northern work fed forward into our 3-D processing and analysis of the Planum Australe 3-D volume, currently under way. We discuss our experiences with these projects and present results and scientific insights stemming from these efforts.
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Affiliation(s)
- Frederick J Foss
- Freestyle Analytical & Quantitative Services, LLC, 2210 Parkview Drive, Longmont, CO 80504
| | - Nathaniel E Putzig
- Planetary Science Institute, 1546 Cole Blvd, Suite 120, Lakewood, CO 80401
| | - Bruce A Campbell
- Smithsonian Institution, MRC 315, PO Box 37012, Washington, DC 20013-7012
| | - Roger J Phillips
- Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, Campus Box 1169, One Brookings Drive, St. Louis, MO 63130-4899
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9
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Carrer L, Bruzzone L. Solving for ambiguities in radar geophysical exploration of planetary bodies by mimicking bats echolocation. Nat Commun 2017; 8:2248. [PMID: 29269728 PMCID: PMC5740182 DOI: 10.1038/s41467-017-02334-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 11/21/2017] [Indexed: 11/22/2022] Open
Abstract
Sounders are spaceborne radars which are widely employed for geophysical exploration of celestial bodies around the solar system. They provide unique information regarding the subsurface structure and composition of planets and their moons. The acquired data are often affected by unwanted artifacts, which hinder the data interpretation conducted by geophysicists. Bats possess a remarkable ability in discriminating between a prey, such as a quick-moving insect, and unwanted clutter (e.g., foliage) by effectively employing their bio-sonar perfected in million years of evolution. Striking analogies occur between the characteristics of bats sonar and the one of a radar sounder. Here we propose an adaptation of the unique bat clutter discrimination capability to radar sounding by devising a novel clutter detection model. The proposed bio-inspired strategy proves its effectiveness on Mars experimental data and paves the way for a new generation of sounders which eases the data interpretation by planetary scientists. Radar sounders, used for the geophysical exploration of celestial objects in the solar system, possess striking similarities to bat sonars. Here, the authors adapt and implement the bat clutter mitigation mechanism to radar geophysical exploration of planetary bodies.
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Affiliation(s)
- Leonardo Carrer
- Department of Information Engineering and Computer Science, University of Trento, Trento, 38123, Italy
| | - Lorenzo Bruzzone
- Department of Information Engineering and Computer Science, University of Trento, Trento, 38123, Italy.
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10
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Phillips RJ, Davis BJ, Tanaka KL, Byrne S, Mellon MT, Putzig NE, Haberle RM, Kahre MA, Campbell BA, Carter LM, Smith IB, Holt JW, Smrekar SE, Nunes DC, Plaut JJ, Egan AF, Titus TN, Seu R. Massive CO
2
Ice Deposits Sequestered in the South Polar Layered Deposits of Mars. Science 2011; 332:838-41. [DOI: 10.1126/science.1203091] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Roger J. Phillips
- Planetary Science Directorate, Southwest Research Institute, Boulder, CO 80302, USA and Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA
| | - Brian J. Davis
- Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, USA
| | - Kenneth L. Tanaka
- Astrogeology Science Center, U.S. Geological Survey, Flagstaff, AZ 86001, USA
| | - Shane Byrne
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
| | - Michael T. Mellon
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA
| | - Nathaniel E. Putzig
- Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, USA
| | - Robert M. Haberle
- Space Science and Astrobiology Division, National Aeronautics and Space Administration (NASA) Ames Research Center, Moffett Field, CA 94035, USA
| | - Melinda A. Kahre
- Bay Area Environmental Research Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
| | - Bruce A. Campbell
- Center for Earth and Planetary Studies, Smithsonian Institution, Washington, DC 20013, USA
| | - Lynn M. Carter
- Science and Exploration Directorate, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - Isaac B. Smith
- Institute for Geophysics, Jackson School of Geosciences, University of Texas, Austin, TX 78758, USA
| | - John W. Holt
- Institute for Geophysics, Jackson School of Geosciences, University of Texas, Austin, TX 78758, USA
| | - Suzanne E. Smrekar
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - Daniel C. Nunes
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - Jeffrey J. Plaut
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | - Anthony F. Egan
- Department of Space Operations, Southwest Research Institute, Boulder, CO 80302, USA
| | - Timothy N. Titus
- Astrogeology Science Center, U.S. Geological Survey, Flagstaff, AZ 86001, USA
| | - Roberto Seu
- Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome, 18-00184 Rome, Italy
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11
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Stillman DE, Grimm RE. Radar penetrates only the youngest geological units on Mars. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010je003661] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Ono T, Kumamoto A, Nakagawa H, Yamaguchi Y, Oshigami S, Yamaji A, Kobayashi T, Kasahara Y, Oya H. Lunar radar sounder observations of subsurface layers under the nearside maria of the Moon. Science 2009; 323:909-12. [PMID: 19213912 DOI: 10.1126/science.1165988] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Observations of the subsurface geology of the Moon help advance our understanding of lunar origin and evolution. Radar sounding from the Kaguya spacecraft has revealed subsurface layers at an apparent depth of several hundred meters in nearside maria. Comparison with the surface geology in the Serenitatis basin implies that the prominent echoes are probably from buried regolith layers accumulated during the depositional hiatus of mare basalts. The stratification indicates a tectonic quiescence between 3.55 and 2.84 billion years ago; mare ridges were formed subsequently. The basalts that accumulated during this quiet period have a total thickness of only a few hundred meters. These observations suggest that mascon loading did not produce the tectonics in Serenitatis after 3.55 billion years ago. Global cooling probably dominated the tectonics after 2.84 billion years ago.
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Affiliation(s)
- Takayuki Ono
- Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
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13
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Holt JW, Safaeinili A, Plaut JJ, Head JW, Phillips RJ, Seu R, Kempf SD, Choudhary P, Young DA, Putzig NE, Biccari D, Gim Y. Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars. Science 2008; 322:1235-8. [PMID: 19023078 DOI: 10.1126/science.1164246] [Citation(s) in RCA: 297] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Lobate features abutting massifs and escarpments in the middle latitudes of Mars have been recognized in images for decades, but their true nature has been controversial, with hypotheses of origin such as ice-lubricated debris flows or glaciers covered by a layer of surface debris. These models imply an ice content ranging from minor and interstitial to massive and relatively pure. Soundings of these deposits in the eastern Hellas region by the Shallow Radar on the Mars Reconnaissance Orbiter reveal radar properties entirely consistent with massive water ice, supporting the debris-covered glacier hypothesis. The results imply that these glaciers formed in a previous climate conducive to glaciation at middle latitudes. Such features may collectively represent the most extensive nonpolar ice yet recognized on Mars.
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Affiliation(s)
- John W Holt
- Institute for Geophysics, Jackson School of Geosciences, University of Texas, Austin, TX 78758, USA.
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Milkovich SM, Plaut JJ. Martian South Polar Layered Deposit stratigraphy and implications for accumulation history. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je002987] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Herkenhoff KE, Byrne S, Russell PS, Fishbaugh KE, McEwen AS. Meter-Scale Morphology of the North Polar Region of Mars. Science 2007; 317:1711-5. [PMID: 17885127 DOI: 10.1126/science.1143544] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Mars' north pole is covered by a dome of layered ice deposits. Detailed ( approximately 30 centimeters per pixel) images of this region were obtained with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter (MRO). Planum Boreum basal unit scarps reveal cross-bedding and show evidence for recent mass wasting, flow, and debris accumulation. The north polar layers themselves are as thin as 10 centimeters but appear to be covered by a dusty veneer in places, which may obscure thinner layers. Repetition of particular layer types implies that quasi-periodic climate changes influenced the stratigraphic sequence in the polar layered deposits, informing models for recent climate variations on Mars.
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Affiliation(s)
- K E Herkenhoff
- Astrogeology Team, United States Geological Survey (USGS), Flagstaff, AZ 86001, USA.
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Zuber MT, Phillips RJ, Andrews-Hanna JC, Asmar SW, Konopliv AS, Lemoine FG, Plaut JJ, Smith DE, Smrekar SE. Density of Mars' South Polar Layered Deposits. Science 2007; 317:1718-9. [PMID: 17885129 DOI: 10.1126/science.1146995] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Both poles of Mars are hidden beneath caps of layered ice. We calculated the density of the south polar layered deposits by combining the gravity field obtained from initial results of radio tracking of the Mars Reconnaissance Orbiter with existing surface topography from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft and basal topography from the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express spacecraft. The results indicate a best-fit density of 1220 kilograms per cubic meter, which is consistent with water ice that has approximately 15% admixed dust. The results demonstrate that the deposits are probably composed of relatively clean water ice and also refine the martian surface-water inventory.
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Affiliation(s)
- Maria T Zuber
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, USA.
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