1. Mars Rover Exploration at Gusev Crater and Back-Ups Characterization and Science Potential of the Sites 2nd 2003 Landing Site Workshop, Pasadena, Ca, Oct. 17-18, 2001 2003 MER Missions to Mars  National Geographic

2. Gusev: Data Coverage Status in Landing Ellipse 13 MOC images (7 during Extended Mission so far) 5 MOLA Tracks Area Covered: ~1,330 km 2 ~50% L. E. currently covered by 1.42 to 5.67 m/pxl res. MOC images Updated Ellipse (10/05/01): 96 x 19 km, Azimuth: 76

3. Hypotheses before MGS F1. Ma’adim Vallis is a fluvial channel Possible alternate hypotheses: role of mass-wasting/fretted channel/glacial processes F2. Ma’adim Vallis has been episodically active throughout Mars’ history- At least 3 main epochs F3. Water from Ma’adim ponded in Gusev generating a series of lakes F4. The mesas at the debouchment of Ma’adim are remnants of a delta F5. The delta was formed under water and ice. At least, one lake was ice- covered --Antarctic analog F6. Early lakes can have been heated by Gusev melt material, later by the formation of 20-km diam. Thyra crater F7. Gusev provides a favorable environment for the preservation of pre-biotic and biotic record-- rapid burial, fine-grained sediments, hydrothermal activity

4. Hypotheses and New Data: MOLA and the Delta of Ma’adim 1 = ap 10942h 2 = ap 10856h 3 = ap 10440h 123

5. Gusev/Ma’adim Interaction and MOC Kuzmin et al., 2000. USGS Map I-2666

6. Fluvio-Lacustrine Activity: Epoch 3 Origin: Epoch 3 deposits from Ma’adim. Youngest deposits in the ellipse. Hypothesis: Last active stage of Ma’adim. Deposits sub- lacustrine or sub-aerial (?) Characteristics: Patches of bright, crusty-like material (Evaporite?). Localized veneers of dust. Flow lobes, few ridges, many outcrops. Occurrence: ~20% of ellipse

7. E03-00012 500 M Res: 2.85m/pxl

8. E05-03287 500 M Res: 2.86m/pxl

9. E05-03287 500 M Res: 2.86m/pxl

10. Lake Sub-aerial deposit Sub-lacustrine (laminations) Sub-aerial episode 2 m 0

11. Science at Ep-3 Deposits to MER Mission (Objectives and Payload) Traceability Matrix

12. Origin: Largest deposit in the ellipse and in Gusev. Originated from Ma’adim. Flat and smooth. Pre-dated Epoch 3 deposits but post-dated delta. Hypothesis: Ice-covered lake episode. Characteristics: Flat and smooth. Degraded craters exposed, Thyra terraces, outcrops Occurrence: 40% of ellipse Fluvio-Lacustrine Activity: Epoch 2

13. M03-02330 400 M Res: 2.84 m/pxl

14. M03-02330 400 M Res: 2.84 m/pxl

15. 300 M M07-00813 Res: 4.26 m/pxl

17. Fluvio-Lacustrine Activity: Contact Epochs 2-1 Origin: Terrain with quasi conical 10-20-m high buttes associated with strongly eroded ~80-m high layered tabular hills. Hypothesis: The morphology of the contact suggests an ice-covered lake Characteristics: Locally rough. Many outcrops covering at least two fluvio-lacustrine epochs (and likely many episodes) Occurrence: ~1% of ellipse

18. 200 M E05-00471 Res: 2.96 m/pxl

19. AHgf1 AHbm1 AHgf1 Marginal Gully Outcrops 250 – 280 m 30 – 50 m 20 – 25º Gully Dimensions ICE Marginal Stream Meltwater E05-00471 300 M Res: 2.96 m/pxl

21. Science at Ep-2 Deposits to MER Mission (Objectives and Payload) Traceability Matrix

22. Fluvio-Lacustrine Activity: Epoch 1 Origin: Material from Ma’adim. Elevation comparable to the delta of the channel. Hypotheses: Remnants of early lacustrine episodes. Lakes possibly heated. Overtopping of Thyra in places? Characteristics: Roughest area in ellipse. Many outcrops composed of small tabular and rounded buttes. Occurrence: ~32% of ellipse

23. E05-01350 270 M Res: 3.36 m/pxl

24. 270 M E05-01350 Res: 2.96 m/pxl

25. Science at Ep-1 Deposits to MER Mission (Objectives and Payload) Traceability Matrix

26. Precursor Epoch 1: Thyra Origin: 20-km diameter impact crater Hypothesis: Pre-date Epoch 1 deposit (outer east rims embedded). Basin filled with Epoch 2 lacustrine deposits. Inner walls may exposed early material and hydrothermally altered minerals Characteristics: Exposed rim walls with some terracing. Occurrence: ~7% of ellipse

27. M03-02330 Res: 2.84 m/pxl

28. Gusev 158 km diam. melt - 10,000 km 3 - location of samples in ellipse: FGusev impact melt and hydrothermally altered material in the rim of Thyra in the center of the ellipse. FGusev rim material ejected from three large craters (36, 31, 15, km diam.) within 2 crater diam. of the ellipse. Thyra 21 km diam., melt 140 km 3 – location of samples: FImpact melt in the rim of Thyra in center of ellipse. 15 km diam. crater on east rim of Gusev, melt 4.7 km 3 - location of samples in ellipse: FImpact melt in ejecta blanket and on the crater rim. Hydrothermal activity and lake deposits

29. Four craters have contributed ejecta material (impact melt and hydrothermal deposits) from the rim of Gusev to the landing site ellipse. Two craters have primary ejecta and their own rim material exposed in or very close to the ellipse. Within the ellipse, the 21 km diam. Thyra may have excavated lake deposits and impact melt from Gusev, and ejecta from the other craters. Craters contributing material to the ellipse within 2 crater diameters

30. Thermal effects of Gusev and craters contributing material to the ellipse within 2 crater diam.

31. Merits of Gusev (Summary) Science F 1. One of the few large basins that had a prolonged, episodic, hydrological history leaving unambiguous and accessible traces of several stages of lacustrine activity F 2. Existing fluvio-lacustrine models and interpretation of facies observed in MOC images frame hypotheses to be tested by the MER science team in a site that is perfectly suited for the MER payload. F 3. Fluvial and lacustrine activity cover most of Mars’ history. Witnessed climate changes F 4. Favorable environment for biological processes (water/energy) and their preservation (fine-grained sediments and chemical sedimentation) Education and Public Outreach F 5. More than 1000 sites on the web about Gusev crater. The crater is being used throughout years by educators in high-schools, universities, and museums to explain students and general public the evolution of water on Mars, the search for life, and the future human colonization. It is familiar to the general public and popular. Varied landscapes: lakebed outcrops, Thyra rim material, mounds, contact between flows

32. Back-Up #1: Boeddicker One 17 km diam. crater has contributed ejecta material (impact melt and hydrothermal deposits) from the rim to the landing site ellipse. Two craters have contributed ejecta to the ellipse. On the edge of the ellipse, the central uplift and crater rims may contain impact melt and hydrothermal deposits from Boeddicker.

33. Back-Up #2: EP69A

34. M23-02043 Res: 5.72 m/pxl

35. M23-02043 300 M Res: 5.72 m/pxl

36. Testing hypotheses with the MER’s payload in EP69A Promising Site Potentially responding at least locally to the requirements of MER’s science objectives and payloads. However, Currently not enough information to understand the nature of the fluvio- lacustrine record and reconstruct its history. Traces of channels and ridges seem to indicate that water could have occupied several regions of the crater. Lack of information prevents the statement of realistic testable hypotheses No obvious layering Excellent prospect for landing and traverse safety if visible morphology is expandable to the rest of the ellipse. Remains a viable back-up if more data can be provided and confirm the preliminary assessment

37. Summary 1 uGusev provides: - An unambiguous record of aqueous activity throughout the landing ellipse - By its interaction with Ma’adim, the possibility to replace the explored materials into their hydro- geological context through time. Many deposits are related to terraces in Ma’adim. Traceable parent-rock regions in watershed. - Testable hypotheses about processes (fluvial, glacial, lacustrine) and resulting landforms and features. - The use of the full range of MER’s science payload to explore a site responding to all MER’s objectives

38. Summary 2 uEPA 69A is a potentially viable back-up but needs more coverage uBoeddicker has little coverage. The evidence for aqueous activity is indirect (regional lobate ejecta craters). Potential for hydrothermal activity. Should not be retained as a back-up at this stage.

39. Acknowledgments People who contributed to this presentation are: –Nathalie Cabrol, NASA Ames Research Center –Edmond Grin, NASA Ames ResearchCenter –David Fike, NASA Ames Research Center –Horton Newsom, University of New Mexico –Ivan Thorsos, University of New Mexico –Rene De Hon, University of North Louisiana –Nadine Barlow, University of Florida Special Thanks to: –The Center for Mars Exploration (CMEX, NASA Ames), Geoffrey Briggs and Virginia Gulick for their support which very much helped the preparation of the presented work.