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The Valley Network Record on Mars (Class 1)

The Valley Network Record on Mars (Class 1). Cold today, cold tomorrow, warm 3.8 billion years ago?. Challenges for our understanding: Climate models have a very hard time raising the Martian surface temperature significantly, even with a thick CO 2 greenhouse

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The Valley Network Record on Mars (Class 1)

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  1. The Valley Network Record on Mars (Class 1)

  2. Cold today, cold tomorrow, warm 3.8 billion years ago? Challenges for our understanding: • Climate models have a very hard time raising the Martian surface temperature significantly, even with a thick CO2 greenhouse Standard stellar evolution models suggest that the solar output was ~70% current at 4 Gya • Mineralogy of surface preserves a record of “easy to weather” volcanic minerals from Early Mars (olivine, pyroxene) • But mineralogy now also reveals a bunch of weathering products!

  3. How do valleys on Earth compare to Mars? On Earth: Erosion linked to surface precipitation and runoff is very important to the shape of the land at local-to-mega-regional scales*,** * even to the point of coupling tectonics to erosion! ** fluvial activity sets the broad form of most surfaces Drainage density is usually >>0.07 km/km2; actual drainage densities are a result of a complicated competition between hillslope (diffusive) and valley-forming (advective) processes. This competition is linked to climate… (Think back to first class). Yemen

  4. Huygens Crater East Rim Region 40E, 20S HRSC 0532 MOLA topography How do valleys on Mars compare to Earth? On Mars: • Valley formation does not appear to have modified the mega-regional scale topography… • Local densities can reach near-terrestrial values, but smallest tributaries are uncommon (Why?) • Valleys do reach to drainage divides (groundwater alone is not a great explanation) • Valleys we observe now are likely >3.5+ Gyr old…(What characteristics can we ascribe to this?)

  5. 500 km Naktong Vallis/ Scamander Vallis Mamers Vallis system (after Irwin et al., 2005). • Some basins appear integrated over length of ~3000-5000 km • Numerous (200+) hydrologically ‘open’ lakes (lakes with outlets) across Mars

  6. What do we want to know? • Intensity • Precipitation[?] rates? • Discharges? • Persistence • Global or local activity? • Long-lived climate or short excursions? • Intermittency? One episode or many? Formation Time (prime topic of next class) • Environmental Requirements (and/or) Implications • Is an ‘ocean’ necessary to support a climate where it rains or snows? Are large lakes good enough?

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