Ice-dust mantles on Mars
David Hollibaugh Baker
NASA Goddard Space Flight Center
SWIM Team Telecon 25 October 2018 Glacial deposits, plains, and mantle units mapped from CTX image mosaic at 1:50,000 scale
Study Area: Deuteronilus Mensae
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 2 Three units mapped in study area
Plains
Mantle
Glacial Deposits
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 3 Morphologic evidence of ~100 m thick mantle unit onlapping glacial deposits
Mantle Mantle
Glacial Deposit
Glacial Deposit Mantle Plains HRSC DTM data
Baker and Head (2015)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 4 Relatively smooth with: Rimless craters.
Small pockmarks or depressions.
Fractures <20 m in width; some forming circular patterns.
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 5 Upl
LDA CTX image P13_006160_2252
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 6 Morphologic evidence of ~100 m thick mantle unit onlapping glacial deposits
Mangold (2003)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 7 Mantle shows collapse features and fractures, possibly related to sublimation of buried ice
Mantle
Mantle
Glacial Deposits
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 8 Middle Amazonian (~500 Ma) age
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 9 Analyzed SHARAD Radargrams
Plains
Mantle
Glacial Deposits
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 10 279 SHARAD tracks analyzed over mantle
SHARAD tracks analyzed
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 11 101 SHARAD tracks showed reflectors
SHARAD tracks with reflectors
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 12 101 SHARAD tracks showed reflectors
Thick and continuous: Thin and Many reflectors patchy: Few reflectors
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 13 Thick occurrences of mantle unit
Glacial Deposits Surrounded by glacial deposits
Isolated Patch
Plains
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 14 Tw o -way time delays show deep and shallow reflectors
shallow
deep
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 15 Histogram of two-way time delays
800 shallow 700 600 500 400 deep 300 Frequency 200 100 0 0 0.75 1.75 2.75 3.75 4.75 5.75 6.75 7.75 8.75 9.75 Two-Way Time Delay (µs)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 16 Shallow reflectors in mantle surrounded by plains
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 17 Reflector traces compared with clutter simulations to confirm source radargram 1μs unit boundaries (PDS, US)
traced 1μs surface radargram clutter reflection subsurface reflector clutter simulation (UT) Choudhary et al. (2016)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 18 Upper plains mantle likely desiccated from original ice content. Consistent with mAl of Skinner et al. (2012) LDA Mantle on ε ~ 5 LDA
Mantle
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 19 Middle Amazonian Lowland Unit (mAl) (Skinner et al., 2012)
LPSC 48, 21 March 2017 - Baker and Carter, Mars Radar Reflectors - 20 Skinner et al. (2012): “Our observations are consistent with the widespread emplacement of a loess-like deposit tens of meters thick in the Martian northern lowlands during the Middle Amazonian due to climate-driven erosion of the north polar plateau”
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 21 Pedestal Craters (Kadish et al., 2009)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 22 Utopia Planitia – Scalloped Terrain
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 23 Utopia Planitia Utopia Planitia Deuteronilus Mensae
Deuteronilus Mensae Utopia Planitia
Continuous Mantle
Thickness of several tens of meters. Highly polygonalized. Latitude-dependent degradation dominated by sublimation and differences in insolation. Lower Plains
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 24 Mantle in Arcadia (Ramsdale et al., 2018) pitted smooth
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 25 Arcadia Expanded Secondaries (Viola et al., 2015)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 26 Hellas Region (LeFort et al., 2010)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 27 Southern Mid-Latitude Scarps (Dundas et al., 2018)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 28 Latitude Dependent Mantle e.g., Mustard et al., 2001; Miliken et al., 2003; Head et al., 2003; Kostama et al., 2006; Schon et al., 2009
Mean crater retention age of 0.1 Ma (Kostama et al., 2006); older at southern latitudes. Thickness of several meters to tens of meters. Desiccation via sublimation at mid- latitude regions during low obliquity excursions.
LPSC 48, 21 March 2017 - Baker and Carter, Mars Radar Reflectors - 29 Dickson et al. (2015)
SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 30 SWIM Telecon, 10/25/2018 - Hollibaugh Baker, Mars Mantle - 31