GEO 416S 2024 Planetary Surface Processes PDF
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2024
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This document contains lecture notes on planetary surface processes, specifically focusing on Mars. It includes announcements, a summary of Mars' surface characteristics, and details about an exam.
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Announcements Exam 3 – Thursday Dec. 5 All assignments need to be submitted before Monday, Dec. 9. Today Surface processes on Mars Discuss/review any questions about Exam 3 GEO 416S Planetary Surface Processes Dec. 3, 2024 Credit: NASA/JPL-Caltech/ASU/MSSS Mars 101...
Announcements Exam 3 – Thursday Dec. 5 All assignments need to be submitted before Monday, Dec. 9. Today Surface processes on Mars Discuss/review any questions about Exam 3 GEO 416S Planetary Surface Processes Dec. 3, 2024 Credit: NASA/JPL-Caltech/ASU/MSSS Mars 101 Avg. Surface T = -63°C (~ -80 ° F) Atmospheric Pressure = 6 mbar [~95% CO2] – ~10’s of precipitable microns of water (Earth is ~cm’s) Mars 101 1877 - Giovanni Schiaparelli maps surface features on Mars, including ‘canali’. Mars 101 Mars101 Article published in The NewYork Times, Dec. 9, 1906 Mars 101 First images of Mars revealed a surface covered in impact craters, more like the Moon than Earth. Leighton et al. (1965) Mars 101 First evidence of (ancient) water is large, eroded river valleys. Valley is >550 km long, Milton (1973) > 5 km wide, and > 800 m deep! Recap… o Atmosphere is 1% of Earth’s and is entirely composed of CO2 o Gravity is 1/3 of Earth’s o Average temperature is-58°F to -76°F o Extremely dry o Now entirely desert TOPOGRAPHY High : 21,171 Low : -8,026 km 14 Alba Mons 12 Olympus 10 Aureole Chryse 8 Planitia Elysium Volcanoes 6 Isidis Tharsis Volcanoes 4 2 Valles Marineris Huygens Noctis 0 Labyrinthus -2 -4 -6 Hellas Argyre -8 Elevation = relative to average planetary radius (or average elevation) Geologic time on Mars GEOLOGICAL TIME SCALE General Timeline of Water on Mars Figure modified from Ehlmann et al. (2011) NOACHIAN SUMMARY Geologic evidence of erosion, transport, and deposition of sediment by water Evidence for flowing water in the geomorphology and rock record Climate was able to support the long- lived surface flows of water and standing bodies of water Noachian was much warmer and wetter than present Mars HESPERIAN Loss of magnetic field (cooling/solidifying of the planet) atmosphere removed/thinned by solar wind Colder and lower surface pressure Availability of liquid water decreased Water started to be buried as ice or evaporated AMAZONIAN Amazonian is 3 billion years up to present Overall cold and dry Geological activity present but waning Volcanism and mega floods occur in the early Amazonian Glacial and ice related activity Now mostly aeolian processes AIR DENSITY ON MARS Yet, we know that sand is notably mobile on Mars surface…. Rubanenko et al (2022) Wind-tunnel experiments have shown that a patch of sand would take winds of about 80 mph to move on Mars compared with only 10 mph on Earth. How do we study the rockrecord on Mars(or any other planet)? Mars Exploration Rovers (Spirit + Opportunity) In the broadest sense, Mars is pretty close to us (trip is ~8 months), so we can send rovers = Mars field geologists! Mars Science Laboratory + Mars 2020 Mars Pathfinder (Curiosity + Perseverance) (Sojourner) Example MSLRover Results– Fluvial Conglomerates Moderately sorted, rounded deposits with D50 ~ 6 mm. Conglomerate of fluvial origin (likely high transport energy)! Williams et al. (2013) Example MSLRover Results– Delta Section Broadly upward coarsening section interpreted as delta stratigraphy. Stack et al. (2019) Grotzinger et al. (2015) Example MSL Rover Results – Sedimentary Rock Fragment Clasts MSL has observed sedimentary rocks containing lithic grains that are themselves sedimentary rock fragments. Sedimentary recycling occurs on Mars as well! Edgett et al. (2020) Example MSLRover Results– Crustal Composition Quartz isnot the mostcommon mineral in Earth’scrust,but it isthe dominant component of siliciclastic sedimentary rockson Earth because it isthe moststable against chemical weathering. 15 ExampleMSLRover Results– Crustal Composition Mars has no continental crust, and so its primary, igneous crust is basalt, which has little to no quartz. Most common sedimentary mineral on Mars is feldspar ➔ this is the most stable siliciclastic mineral! 16 Example Mars2020 Rover Results – Clinoform Strata Mangold et al. (2021) ExampleMars2020 Rover Results –Clinoform Strata Mangold et al. (2021) 18 Example Mars2020 Rover Results – Clinoform Strata Clinoform strata interpreted as a full deltaic section. Is this uniquely true? Mangold et al. (2021) 19 Howdowestudythe rockrecordonMars(oranyother planet)? Rovers are expensive, so most of the data we have is from satellites, which give us really high-resolution images of the martian surface. Goudge et al. (2018) ExampleOrbital Results–ThickSedimentarySections Sections of sedimentary rock that are hundreds of meters to kilometers thick! Grotzinger and Milliken (2011) ExampleOrbital Results–CraterEmbeddedin SedimentaryRock Grotzinger and Milliken (2011) ExampleOrbital Results–ModernDune Migration Chojnacki et al. (2019) Exploring Early Mars’Sedimentary Record Prominent class of sedimentary outcrop on Mars is fan deposits. Commonly interpreted as deltas based on modern morphology. [e.g., Ori, et al., 2000; Bhattacharya, et al., 2005; DiAchille et al., 2006; Hauber et al., 2009; Di Achille and Hynek, 2010] Wilson et al. ExploringEarlyMars’SedimentaryRecord Assumestopographic equivalency with their original geomorphic form... Wilson et al. Yukon River Delta ExploringEarly Mars’Sedimentary Record BAD assumption – these deposits are rock! Really a Q for stratigraphy. Wilson et al. Yukon River Delta Depositional environment is recorded in stratigraphic architecture, which not directly modified by later outcrop erosion. Work by Michelle Tebolt Tebolt et al. [in revision] Depositional Depositional environment isrecordedin environment is recorded in stratigraphic architecture, which not directly modified by later outcrop erosion. Work by Michelle Tebolt How do we get stratigraphic architecture from orbit?? Tebolt et al. [ in revision] Stratigraphy from Orbit Vertical Exaggeration = 2x Stratigraphy from Orbit Vertical Exaggeration = 2x Stratigraphy from Orbit Vertical Exaggeration = 2x Stratigraphy Plane from Orbit fits provide measurement of layer orientation (i.e., strike and dip). Vertical Exaggeration = 2x Global study reveals far fewer deltas than previously inferred. Delta (n = 5) Alluvial Fan (n = 17) Tebolt and Goudge Why so few deltas? More scrutinous study of stratigraphic architecture indicates delta deposits are rarer than previously thought. This suggests either: 1. Standing water was less common on Mars than previously thought. But LOTSof other evidence for lakes, including many without fan deposits… 2. The picture of Mars’ sedimentary record, as viewed from orbit, is highly incomplete. Water world to a wind world Figure modified from Ehlmann et al. (2011) Wind: Now the dominant mechanism for sediment transport on Mars https://youtu.be/g9LdxG-cJhY https://youtu.be/g9LdxG-cJhY Example MSLRover Results– Aeolian Cross-Strata Sets of stacked cross-strata record migration of ancient aeolian dunes. Banham et al. (2018) Subtitle Subtitle Open the Design Ideas pane for instant slide makeovers. When we have design ideas, we’ll show them to you right there. 1964 1971 Mariner 4: first images of Mars surface Mariner 9: branching valleys, volcanoes, and dune fields FIRST IMAGES 50 km 10 km 48 Noachian River networks Meandering channels, cut-off meander, crisscrossing channels Gale crater Jezero crater Perseverance landing site Curiosity landing site