Geological Diversity within 500 m Radius MER Landing Spots: Comparison Among Landing Ellipses

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Geological Diversity within 500 m Radius MER
Landing Spots Comparison Among Landing Ellipses

• Robert Sullivan
• Jon Branscomb
• R. Alan Faquet
• Michael Fergen
• John A. Peterson
• Larry Soderblom
• Steve Squyres

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Purpose of Study
Action item from last MER Athena team meeting
Evaluate the probability of landing within rover
traverse distance of interesting terrain in the
leading candidate landing ellipses.
local area of high scientific interest
(e.g., layered outcrops, anomalous surface
materials)
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Approach to Problem

• Apply 500 m radius landing spots throughout the
  leading candidate landing ellipses according to
  the appropriate probability function
• Evaluate the potential science interest and
  diversity in each of these spots using MOC
  images, where available.

Gale ep82a
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Image Preparation

• MOC images prepared by USGS (L.
  Soderblom, M. Fergen)
• 16-bit ISIS cubes
• 8-bit TIFF with albedo scaled 0.0-0.4 -gt 0-255 DN
  (with a few exceptions)
• 500 m radius landing site spots distributed
  across landing ellipses (J. Branscomb)
• Size and orientation of landing ellipses
  according to Golombek Grant memorandum of
  September 6 (earlier trials/work using earlier
  sizing was discarded). Latest ellipses are 5-10
  larger.

Eos Chasma vm41a MOC e0300738 Spots 1-6
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Evaluation Criteria
Ratings used an integer scale of 1 (worst) to 5
(best). Criteria were established during trial
exercises using images from all ROTO ellipses.
Factors decreasing the potential scientific value
of a landing spot

• Smoothness. No landmarks for navigation, no
  place to climb for a local field-geologist
  overview
• Dustiness. (e.g., as indicated by dust devil
  tracks) Might have to do a lot of RATing for IDD
  tools to be productive spectral productivity of
  Pancam and MTES degraded
• Homogeneity of albedo and/or morphology
• Dunes distributed closely enough to hamper
  directional freedom, reducing achievable
  diversity within spot
• Surface morphologies in degradational states only
  (e.g., all craters are shallow, infilled, with
  unrecognizable ejecta blankets and low, degraded
  rims) gt less probability of locating coherent
  rock samples

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Evaluation Criteria
Factors increasing the potential scientific value
of a landing spot

• Relief which exposes layering or defines layering
• Relief exterior to the spot that could still be
  observed by Pancam and MTES
• Albedo contrasts suggesting the presence of
  bedrock exposures of more than one geological
  unit as well as minimal dustiness
• Dunes composed of material that is appears to be
  different from the substrate on which they rest
  (but dunes not so densely distributed as to
  seriously degrade directional freedom)
• Well-preserved evidence for processes (e.g.,
  fluid erosion, slope evolution, impact cratering,
  lava flow emplacement) that could provide
  fundamental information about how these processes
  operate on Mars
• Impact craters sufficiently well-preserved to
  increase the potential for locating blocks within
  continuous ejecta (get coherent rock samples)

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Evaluation Criteria
Characteristics that were not factors in these
evaluations
The following characteristics are very important,
but are left as future layers of analysis that
can be convolved later with the results of this
study.

• Hematite abundance (TES map)
• Basalt abundance (TES map)
• Andesite abundance (TES map)
• Landing hazards
• Potentially controversial interpretations
  regarding subaqueous vs. subaerial deposition of
  layered sedimentary units

Image details found only within each landing site
(or readily in view from within site boundaries)
were emphasized over regional geological
interpretations. For example, two sites with
identical appearances, one with strong hematite
abundance, one without, will receive the same
rating.
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Evaluation Criteria
Characteristics that were not factors in these
evaluations (continued)
Likewise, essential landing hazard assessments
are left to be superimposed later on the results
of this study once specific, refined hazard
criteria are available. For example, layering
exposed in prominent relief will increase the
scientific interest of a site, despite the hazard
such relief may pose to a safe landing future
assessments dedicated specifically to landing
hazards may rule the site out on those grounds
despite its scientific potential.
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Example of a 1
Dominated by closely spaced duneforms/drifts,
degrading EW trafficability. No other features,
relief. No albedo contrasts. (Melas vm53a,
image e0200270, spot5)
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Example of a 1
Nearly featureless plain, with only subtle,
ambiguous relief. No albedo contrasts. (Eos
Chasma vm41a, image e0300738, spot2)
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Example of a 1
Smooth, nearly featureless plain. Craters are
very few, very small. Small, slightly brighter
patches occur in N. (Hematite tm10a, image
e0101056, spot4)
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Example of a 2
Smooth, nearly featureless plain in E, S, W, but
slope break into shallow depression occurs in N,
extending beyond the N margin to the depressions
center 1 km from N margin. Within site,
indistinct patches of brighter material in center
and perhaps along slope break in N, secondary
crater cluster in SW (largest 50 m)..
(Hematite tm10a, image m0301632, spot2)
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Example of a 3
Rugged, but heavily eroded terrain. Small
isolated mesas do not display obvious bedding on
their walls, but nonetheless a roughly consistent
height among them suggests remnants of a single
layer that is being or was being stripped.
Concave-up slope breaks are rounded, suggesting
the presence of a mantling layer dominate the
lower-lying areas. No albedo contrasts. (Gusev
ep55a, image e0301511, spot3)
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Example of a 4
Two units S third of site composed of spurred
knobs appears to be in the process of exhumation
from beneath slightly less rugged unit in N two
thirds of landing site. (Gale ep82a, image
e0402461, spot3)
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Example of a 5
Several obviously layered units revealed on the
basis of both albedo contrasts and differential
erosion. Closely spaced bright duneforms/drifts
in extreme N and W can be easily avoided.
(Melas vmBsite, image m2301183, spot7)
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Example of a 5
Several units distinguished on the basis of
albedo and textural contrasts. Closely spaced
duneforms/drifts in W easily avoided if
necessary. Fantastic. (Melas vmBsite, image
m0804367, spot1)
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Summary of Results
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Summary of Results