Oxia Planum, landing site for Mars 2020 P.Thollot1, C. Quantin1, J. Carter2, D. Loizeau1 and B. Bultel1

Mars 2020 First Landing Site Workshop May 14–16, 2014, Crystal City, VA

(1) Laboratoire de Géologie de Lyon, France (2) IAS, France

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Oxia Planum location

Mawrth Vallis

Meridiani

Chryse

Valles Marineris

Oxia Planum

Oxia Planum, wide clay-bearing plain

Mawrth Vallis

Ares Vallis

Oxia Planum, wide clay-bearing unit

OMEGA+CRISM MSP-Mapping criteria : 2.3 microns band , Mg/Fe Phyllosilicates

Geological context: Noachian age

Crater counts on Oxia-Mawrth region

- Oxia-Mawrth Region is 4 Gy (+/- 200 My) old - Intense crater obliteration from 4 Ga to 3.6 Ga - Moderate but continuous erosion since 3.6 Ga

Geological context: morphology

Coogoon outflow channel

Fan deposit

Ridged unit

Channels

Basement unit

Basement unit

Geological context: hydrated minerals Red: Fe-bearing phyllosilicates

Outline of 25x20 km Landing Ellipse

CRISM MSP 100m/pix

Fe/Mg-Phyllo unit

Fe/Mg-Phyllo unit

Fe/Mg-Phyllo unit

Mawrth-Vallis- like stratigraphy

Geological context: evidence for volcanism

Large Caldeira detected further north in Arabia Terra

(Michalski and Bleacher, 2013)

Geological context: Fan shaped deposit in paleo-basin at the mouth of Coogoon Valles

Fan deposit

Coogoon Vallis N outlet

Paleo-basin outline ?

Ejecta blanket

Coogoon Vallis S outlet

Runoff channel ?

Runoff channel ?

Bedrock unit

Bedrock unit

Capping unit

Geological context: Fan shaped deposit in paleo-basin at the mouth of Coogoon Valles

Fan deposit

Coogoon Vallis N outlet

Paleo-basin outline ?

Ejecta blanket

Coogoon Vallis S outlet

Runoff channel ?

Runoff channel ?

Bedrock unit

Bedrock unit

Capping unit

Zoom on divergent Finger-like terminations Flat surface and No obvious channels : subaquous delta fans ?

Fan shaped deposit

1 km

Geological context: Fe/Mg-phyllosilicates, hydrated silica/kaolinite

Red: Fe-bearing minerals

Yellow: Fe/Mg-phyllosilicates

Blue: Si-OH/Al-OH

CRISM MSP 100m/pix Low S/N

CRISM FRT 20m/pix high S/N

Fan deposit

South route: proximal fan deposits and bedrock stratigraphies

Possible long term target: bright layered deposits (‘Mawrth-like’)

Capping unit: lava flows

25x20 km Landing Ellipse

Bedrock unit

Bedrock unit

Fan deposits

Red: Fe-bearing phyllosilicates East route: distal fan deposits stratigraphy

Possible traverse routes from ellipse center

Red: Fe-bearing phyllosilicates

Land on Fe/Mg-Phyllo bearing unit

Land on Fe/Mg-Phyllo bearing unit

Dark capping unit, retreating southward

Fan deposits

Most recent exposures of phyllo-bearing outcrops

Center of Landing Ellipse

Possible traverse routes

Red: Fe-bearing phyllosilicates

+1 km +2.5 km

Land on Fe/Mg-Phyllo bearing unit: morphology

Polygonally fractured surface: probable dessication cracks: Depositional and/or diagenetic

Smooth material: probable erosion of fractured unit and/or removed capping unit > favorable for roving

NB: No HiRISE on ellipse center: shown here is a sample of the same unit ~4 km to the East

Capping unit: prob. lava flows currently eroding away: young exposure age

Dark capping unit, retreating Recent exposure of

Fe/Mg-phyllo-bearing unit

Red: Fe-bearing phyllosilicates

+9 km

+5/+8 km Fan deposits

Fan deposits stratigraphy exposed in craters

South route: Exposed stratigraphy of proximal fan deposits

Red: Fe-bearing phyllosilicates

+10 km

Basement unit: Fe/Mg-phyllo bearing South route Fan deposits

Fe/Mg-Phyllo basement unit

+10 km

Red: Fe-bearing phyllosilicates

+10 km

Basement unit: Fe/Mg-phyllo bearing South route

Fe/Mg-phyllo signatures

Fe/Mg-Phyllo basement unit

+12 km

Red: Fe-bearing phyllosilicates

+15.5 km

Late lava flow, associated aqueous alteration, stratigraphic relationship w/ Fe/Mg-phyllo unit

South route

+15.5 km

Coogoon Vallis lava flow

(= capping unit ?)

Fe/Mg-phyllo basement unit

Si-OH signatures

Red: Fe-bearing phyllosilicates

+21 km +24 km

+17 km

+20 km

Possible long term target: bright layered deposits with similar stratigraphy as Mawrth Vallis

Coogoon Vallis lava flow

(= capping unit ?)

Fe/Mg-phyllo basement unit

Si-OH signatures

+21 km

+17 km Mawrth Vallis – like

Layered deposits

East route

South route

Current datasets coverage

HiRISE CRISM

CTX HRSC

HiRISE

Lon. , Lat.

-23.98,17.80 -24.00,17.97 -24.08,17.84 -23.91,18.04 -23.80,17.88 -24.01,17.66 -23.81,17.69 -23.72,17.70

CRISM

Lon. , Lat.

-23.75,17.71 -23.94,17.88 -23.95,18.01

Target requests

Oxia Planum Essentials • Surface aqueous alteration of basement unit: Fe/Mg-Phyllosilicates

• Noachian age: ~4 Ga; units overlain by Hesperian Ridged plains

• Noachian fan-shaped sedimentary deposits in paleobasin: delta ? fossil river channels in basement unit

• Igneous units, Noachian and/or Hesperian (lava flows, caldeiras)

• Ancient capping unit: altered basement and deposits shielded from later alteration

• Recent erosion of capping unit exposing preserved older units

• Prob. Mawrth-Vallis-like stratigraphy on basement, as close as 4 km from ellipse

• Exomars candidate landing site (potential exploration synergy)