Sedimentary Fans in the Nili Fossae Region: Evidence for Lacustrine Sedimentation and the Persistent Flow of Water on Mars

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Deltas and related sedimentary deposits A key
class of landing sites for the MSL Mission J.L.
Dickson, C.I. Fassett, J.W. Head, M.A.
Kreslavsky, J.B. Madeleine and M.I. Ivanov
(Brown University)
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MSL Science Objectives
Primary science objectives for Mars Science
Laboratory - Assess the biological potential of
at least one target environment. - Characterize
the geology and geochemistry of the landing
region. - Investigate planetary processes of
relevance to past habitability.

• Deltaic environments offer the greatest
• potential for achieving these objectives
• - Deltas suggest standing bodies of water in the
  past, increasing the potential for habitability.
• Smooth deposits on crater floors offer ideal
  locations for landing of MSL and traversing.
• Here, we propose two separate landing sites that
  offer the greatest chance to achieve the
  scientific objectives.
• Nili Fossae crater lake deposits.
• Eberswalde crater fan deposits.

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1. Nili Fossae Crater Lake Deposits
THEMIS IR Daytime Mosaic w/ MOLA Color Topography
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Nili Fossae Crater Fan Deposits

• Two prominent fan deposits found in this 40-km
  diameter crater at mouths of entering streams.
• Total Area of two fans 56 km2.
• Outlet channel implies filled crater lake.

THEMIS IR Daytime Mosaic w/ MOLA Color Topography
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Influx Crater Fan Deposits
Mosaic of MOC images R23/00833 and S04/00725.
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Crater Lake Filling and Outflow

• The present minimum elevation of the outlet is
  higher than almost all of the crater floor,
  including the fan deposits.
• This -2390 contour represents the minimum lake
  stand (assuming present topography).
• Maximum depth of the minimum stand gt300 m.
• Sediments also deposited on crater floor from
  suspension.

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Qualitative Indicators of Persistent Flow

• Mineralogy Hydration and clay signatures are
  observed in OMEGA data within the watershed of
  the Nili Fossae delta deposits.

Hydration
Clay
Mustard et al., OMEGA team 2005
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2. Eberswalde Crater Fan Deposits
Similar sedimentary fans and floor deposits.
Malin and Edgett, 2003 Moore et al., 2004
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Eberswalde Crater
10 km reference traverse (right) demonstrates
access to key units.
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Eberswalde Crater - Engineering
Low Slope 99.4 of MOLA point-to-point slopes are
below 10, with the only steep slopes on the
margin of the crater.
Low Elevation Elevation of floor is -1500 m,
well below the threshold for landing. High
Thermal Inertia Lowest values at 400 J/m2K
s1/2. Low Albedo All values lt 0.20.
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Implications of the Nili Fossae Crater Lake and
Eberswalde Crater Fan and Floor Deposits

• Persistent surface water was probably required to
  form the observed deposits.
• Each site has preserved, accessible sedimentary
  deposits. Date to Late Noachian-Hesperian.
• Terrain surrounding the fan deposits is flat at
  all measurable baselines, providing a safe
  location for landing and traverse.
• These sites fall under the category of
  fluvio-deltaic and/or lacustrine settings
  propsed as optimal by Golombek and Grotzinger
  (this conference).
• These types of sites merit further investigation.