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Chojnacki M, Vaz DA, Silvestro S, Silva DCA. Widespread Megaripple Activity Across the North Polar Ergs of Mars. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2021; 126:e2021JE006970. [PMID: 35096495 PMCID: PMC8793034 DOI: 10.1029/2021je006970] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
The most expansive dune fields on Mars surround the northern polar cap where various aeolian bedform classes are modified by wind and ice. The morphology and dynamics of these ripples, intermediate-scale bedforms (termed megaripples and Transverse Aeolian Ridges [TARs]), and sand dunes reflect information regarding regional boundary conditions. We found that populations of polar megaripples and larger TARs are distinct in terms of their morphology, spatial distribution, and mobility. Whereas regionally restricted TARs appeared degraded and static in long-baseline observations, polar megaripples were not only widespread but migrating at relatively high rates (0.13 ± 0.03 m/Earth year) and possibly more active than other regions on Mars. This high level of activity is somewhat surprising since there is limited seasonality for aeolian transport due to surficial frost and ice during the latter half of the martian year. A comprehensive analysis of an Olympia Cavi dune field estimated that the advancement of megaripples, ripples, and dunes avalanches accounted for ~1%, ~10%, and ~100%, respectively, of the total aeolian system's sand fluxes. This included dark-toned ripples that migrated the average equivalent of 9.6 ± 6 m/yr over just 22 days in northern summer-unprecedented rates for Mars. While bedform transport rates are some of the highest yet reported on Mars, the sand flux contribution between the different bedforms does not substantially vary from equatorial sites with lower rates. Seasonal off-cap sublimation winds and summer-time polar storms are attributed as the cause for the elevated activity, rather than cryospheric processes.
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Affiliation(s)
| | - David A Vaz
- Centre for Earth and Space Research of the University of Coimbra, Observatório Geofísico e Astronómico da Universidade de Coimbra, Coimbra, Portugal
| | - Simone Silvestro
- SETI Institute, Carl Sagan Center, Mountain View, CA, USA
- INAF Osservatorio Astronomico di Capodimonte, Napoli, Italia
| | - David C A Silva
- Centre for Earth and Space Research of the University of Coimbra, Observatório Geofísico e Astronómico da Universidade de Coimbra, Coimbra, Portugal
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Rodriguez JAP, Tanaka KL, Bramson AM, Leonard GJ, Baker VR, Zarroca M. North polar trough formation due to in-situ erosion as a source of young ice in mid-latitudinal mantles on Mars. Sci Rep 2021; 11:6750. [PMID: 33767212 PMCID: PMC7994824 DOI: 10.1038/s41598-021-83329-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 01/28/2021] [Indexed: 11/24/2022] Open
Abstract
The clockwise spiral of troughs marking the Martian north polar plateau forms one of the planet’s youngest megastructures. One popular hypothesis posits that the spiral pattern resulted as troughs underwent poleward migration. Here, we show that the troughs are extensively segmented into enclosed depressions (or cells). Many cell interiors display concentric layers that connect pole- and equator-facing slopes, demonstrating in-situ trough erosion. The segmentation patterns indicate a history of gradual trough growth transversely to katabatic wind directions, whereby increases in trough intersections generated their spiral arrangement. The erosional event recorded in the truncated strata and trough segmentation may have supplied up to ~25% of the volume of the mid-latitude icy mantles. Topographically subtle undulations transition into troughs and have distributions that mimic and extend the troughs’ spiraling pattern, indicating that they probably represent buried trough sections. The retention of the spiral pattern in surface and subsurface troughs is consistent with the megastructure’s stabilization before its partial burial. A previously suggested warm paleoclimatic spike indicates that the erosion could have occurred as recently as ~50 Ka. Hence, if the removed ice was redeposited to form the mid-latitude mantles, they could provide a valuable source of near-surface, clean ice for future human exploration.
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Affiliation(s)
- J Alexis P Rodriguez
- Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ, 85719-2395, USA.
| | - Kenneth L Tanaka
- Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ, 85719-2395, USA
| | - Ali M Bramson
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Dr, West Lafayette, IN, 47907, USA
| | - Gregory J Leonard
- Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, 85721, USA
| | - Victor R Baker
- Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, 85721, USA.,Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, 85721, USA
| | - Mario Zarroca
- External Geodynamics and Hydrogeology Group, Department of Geology, Autonomous University of Barcelona, 08193, Bellaterra, Barcelona, Spain
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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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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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Smith IB, Putzig NE, Holt JW, Phillips RJ. An ice age recorded in the polar deposits of Mars. Science 2016; 352:1075-8. [PMID: 27230372 DOI: 10.1126/science.aad6968] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 04/19/2016] [Indexed: 11/02/2022]
Abstract
Layered ice deposits at the poles of Mars record a detailed history of accumulation and erosion related to climate processes. Radar investigations measure these layers and provide evidence for climate changes such as ice advance and retreat. We present a detailed analysis of observational data showing that ~87,000 cubic kilometers of ice have accumulated at the poles since the end of the last ice age ~370,000 years ago; this volume is equivalent to a global layer of ~60 centimeters. The majority of the material accumulated at the north pole. These results provide both a means to understand the accumulation history of the polar deposits as related to orbital Milankovitch cycles and constraints for better determination of Mars' past and future climates.
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Affiliation(s)
- Isaac B Smith
- Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, USA.
| | - Nathaniel E Putzig
- Department of Space Studies, Southwest Research Institute, Boulder, CO 80302, USA
| | - John W Holt
- University of Texas Institute for Geophysics, Jackson School of Geosciences, University of Texas, J. J. Pickle Research Campus, Austin, TX 78758, USA
| | - Roger J Phillips
- Planetary Science Division, Southwest Research Institute, Boulder, CO 80302, USA. McDonnell Center for the Space Sciences and Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA
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Moore JM, McKinnon WB, Spencer JR, Howard AD, Schenk PM, Beyer RA, Nimmo F, Singer KN, Umurhan OM, White OL, Stern SA, Ennico K, Olkin CB, Weaver HA, Young LA, Binzel RP, Buie MW, Buratti BJ, Cheng AF, Cruikshank DP, Grundy WM, Linscott IR, Reitsema HJ, Reuter DC, Showalter MR, Bray VJ, Chavez CL, Howett CJA, Lauer TR, Lisse CM, Parker AH, Porter SB, Robbins SJ, Runyon K, Stryk T, Throop HB, Tsang CCC, Verbiscer AJ, Zangari AM, Chaikin AL, Wilhelms DE. The geology of Pluto and Charon through the eyes of New Horizons. Science 2016; 351:1284-93. [PMID: 26989245 DOI: 10.1126/science.aad7055] [Citation(s) in RCA: 184] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than ~10 million years. Surrounding terrains show active glacial flow, apparent transport and rotation of large buoyant water-ice crustal blocks, and pitting, the latter likely caused by sublimation erosion and/or collapse. More enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures. Pluto also has ancient cratered terrains up to ~4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes. Charon does not appear to be currently active, but experienced major extensional tectonism and resurfacing (probably cryovolcanic) nearly 4 billion years ago. Impact crater populations on Pluto and Charon are not consistent with the steepest impactor size-frequency distributions proposed for the Kuiper belt.
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Affiliation(s)
- Jeffrey M Moore
- National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA.
| | - William B McKinnon
- Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA
| | | | - Alan D Howard
- Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA
| | - Paul M Schenk
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | - Ross A Beyer
- The SETI Institute, Mountain View, CA 94043, USA. National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
| | | | | | - Orkan M Umurhan
- National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
| | - Oliver L White
- National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
| | - S Alan Stern
- Southwest Research Institute, Boulder, CO 80302, USA
| | - Kimberly Ennico
- National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
| | - Cathy B Olkin
- Southwest Research Institute, Boulder, CO 80302, USA
| | - Harold A Weaver
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
| | | | | | - Marc W Buie
- Southwest Research Institute, Boulder, CO 80302, USA
| | | | - Andrew F Cheng
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
| | - Dale P Cruikshank
- National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
| | | | | | | | | | | | | | - Carrie L Chavez
- The SETI Institute, Mountain View, CA 94043, USA. National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA
| | | | - Tod R Lauer
- National Optical Astronomy Observatory, Tucson, AZ 85719, USA
| | - Carey M Lisse
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
| | | | - S B Porter
- Southwest Research Institute, Boulder, CO 80302, USA
| | | | - Kirby Runyon
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
| | - Ted Stryk
- Roane State Community College, Oak Ridge, TN 37830, USA
| | | | | | - Anne J Verbiscer
- Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
| | | | | | - Don E Wilhelms
- U.S. Geological Survey, Retired, Menlo Park, CA 94025, USA
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MacGregor JA, Fahnestock MA, Catania GA, Paden JD, Prasad Gogineni S, Young SK, Rybarski SC, Mabrey AN, Wagman BM, Morlighem M. Radiostratigraphy and age structure of the Greenland Ice Sheet. JOURNAL OF GEOPHYSICAL RESEARCH. EARTH SURFACE 2015; 120:212-241. [PMID: 26213664 PMCID: PMC4508962 DOI: 10.1002/2014jf003215] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 01/14/2015] [Indexed: 05/25/2023]
Abstract
UNLABELLED Several decades of ice-penetrating radar surveys of the Greenland and Antarctic ice sheets have observed numerous widespread internal reflections. Analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections. Here we present a comprehensive deep radiostratigraphy of the Greenland Ice Sheet from airborne deep ice-penetrating radar data collected over Greenland by The University of Kansas between 1993 and 2013. To map this radiostratigraphy efficiently, we developed new techniques for predicting reflection slope from the phase recorded by coherent radars. When integrated along track, these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing. Core-intersecting reflections were dated using synchronized depth-age relationships for six deep ice cores. Additional reflections were dated by matching reflections between transects and by extending reflection-inferred depth-age relationships using the local effective vertical strain rate. The oldest reflections, dating to the Eemian period, are found mostly in the northern part of the ice sheet. Within the onset regions of several fast-flowing outlet glaciers and ice streams, reflections typically do not conform to the bed topography. Disrupted radiostratigraphy is also observed in a region north of the Northeast Greenland Ice Stream that is not presently flowing rapidly. Dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly. This radiostratigraphy provides a new constraint on the dynamics and history of the Greenland Ice Sheet. KEY POINTS Phase information predicts reflection slope and simplifies reflection tracingReflections can be dated away from ice cores using a simple ice flow modelRadiostratigraphy is often disrupted near the onset of fast ice flow.
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Affiliation(s)
- Joseph A MacGregor
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA
| | - Mark A Fahnestock
- Geophysical Institute, University of Alaska Fairbanks Fairbanks, Alaska, USA
| | - Ginny A Catania
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - John D Paden
- Center for Remote Sensing of Ice Sheets, The University of Kansas Lawrence, Kansas, USA
| | - S Prasad Gogineni
- Center for Remote Sensing of Ice Sheets, The University of Kansas Lawrence, Kansas, USA
| | - S Keith Young
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - Susan C Rybarski
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA ; Now at Division of Hydrologic Sciences, Desert Research Institute Reno, Nevada, USA
| | - Alexandria N Mabrey
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - Benjamin M Wagman
- Institute for Geophysics, The University of Texas at Austin Austin, Texas, USA ; Department of Geological Sciences, University of Texas at Austin Austin, Texas, USA
| | - Mathieu Morlighem
- Department of Earth System Science, University of California Irvine, California, USA
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Nunes DC, Smrekar SE, Fisher B, Plaut JJ, Holt JW, Head JW, Kadish SJ, Phillips RJ. Shallow Radar (SHARAD), pedestal craters, and the lost Martian layers: Initial assessments. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010je003690] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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