1. Open Basin Lakes: Surface Water Inventories and Sources of Water

2. Open vs. Closed Basins Lakes that were once hydrologically open (basins with outlets) allow: Confident recognition of where water ponded Measurement of the minimum volume of water required (to activate an outlet valley) In basins without clearly incised outlets, we cannot be sure that water ponded. Closed Basin Open Basin

3. Open Basin Locations

5. Parameters Measured All lakes: Connections to other lakes (lake chains) Elevation Area, volume, perimeter Morphological characteristics (resurfacing? sedimentary deposits? ) Where possible: Watershed Area

6. Lake Size

7. Eridania Basin Ma’adim Vallis (to Gusev Crater) V=213000 km 3, WA=2080000 km 2, V/A w =102 m Irwin et al., 2002 (Science)

8. Lake Volume / Watershed Area Volume/Watershed Area = a measure of the water that was delivered to the lake per unit area of the watershed If groundwater is negligible, this is the integrated precipitation amount over time (in excess of evaporation / infiltration) necessary to flood the basin. in meters Eridania

9. Lake Volume / Watershed Area Cassini Crater V=30000 km 3 WA=155000 km 2 V/A w =200 m in meters Cassini

10. in meters Antoniadi Crater V=31000 km 3 WA=555000 km 2 V/A w =56 m Lake Volume / Watershed Area Antoniadi

11. Many basins that remained closed have V/A w ~20-30 m. Lake Volume / Watershed Area 128.75E, 8.3S V=1700 km 3 WA=61000 km 2 V/A w =28 m 88.25E, 3.25S V=400 km 3 WA=17000 km 2 V/A w =23 m

12. Lake Volume / Watershed Area 1. Especially high local ‘excess’ precipitation (*unlikely*), OR 2. A regional (non-local!) groundwater contribution to flooding the basin. Given that closed basins had V/A w ~20-30 m, open basins with high V/A w either had to have: in meters

13. Anomalies in V/A w are: i) larger lakes than is typical ii) generally at low elevations iii) most are concentrated in “greater Arabia” (70%) Symbol size proportional to V/A w Lake Volume / Watershed Area

14. Andrews-Hanna et al., 2008 Modeled Evaporation Rate (10-4 m/yr): a proxy for where groundwater reaches surface

15. Broad regional agreement between where models expect groundwater to outcrop and where we observe it. Some differences (e.g., for largest lakes): Cassini & Eridania clearly resolved as net positive groundwater flux. Antoniadi+Tikhonravov, not resolved in regional models, but seen in higher res. models Andrews-Hanna et al., 2008

16. Lake/Watershed properties & modeling suggest an important role for groundwater input to some lakes Lakes that are not anomalies in V/A w have volume proportional to watershed area: consistent with local precipitation + local precipitation-recharged groundwater as water sources. Water Source

17. Resurfacing of large lake floors Hesperia Planum MOLA Roughness MOLA Roughness data Kreslavsky and Head, 2000 The rule, not the exception. >50% of catalogued lakes mapped have textures & morphological indicators of post-lacustrine resurfacing.

18. Resurfacing of large lake floors Goldspiel and Squyres (1991) recognized that “in many instances, the sedimentation basin floors appear to be covered by volcanic extrusions...post- dat[ing] the period of fluvial activity.” “Other features to note...[are] the signs of volcanic extrusions on the crater floor.” The rule, not the exception. >50% of catalogued lakes mapped have textures & morphological indicators of post-lacustrine resurfacing.