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

1. 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

2. 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)

3. 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

4. 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 -> 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

5. Evaluation Criteria • 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) ==> less probability of locating coherent rock samples 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:

6. Evaluation Criteria • 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) Factors increasing the potential scientific value of a landing spot:

7. Evaluation Criteria • 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 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. 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.

8. 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.

9. Example of a “1” “Dominated by closely spaced duneforms/drifts, degrading EW trafficability. No other features, relief. No albedo contrasts.” (Melas vm53a, image e0200270, spot#5)

10. Example of a “1” “Nearly featureless plain, with only subtle, ambiguous relief. No albedo contrasts.” (Eos Chasma vm41a, image e0300738, spot#2)

11. 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, spot#4)

12. 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 depression’s 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, spot#2)

13. 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, spot#3)

14. 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, spot#3)

15. 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, spot#7)

16. 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, spot#1)

17. Summary of Results

18. Summary of Results