Ice-dust mantles on

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 (~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 – 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