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Chapter 7 Earth and the Terrestrial Worlds Slide 2 Why is Venus so hot? Slide 3 Thought Question What is the main reason why Venus is hotter than Earth? A. Venus is closer to the Sun than Earth. B. Venus is more reflective than Earth. C. Venus is less reflective than Earth. D. The greenhouse effect is much stronger on Venus than on Earth. E. Human activity has led to declining temperatures on Earth. Slide 4 Venus in UV light Slide 5 Venus mapped with Radar Slide 6 The surface of Venus Slide 7 Venus surface Venera Probes from 1970s survived for minutes Slide 8 Venus surface Venera Probes from 1970s survived for minutes Slide 9 Slide 10 Slide 11 Slide 12 Does Venus have plate tectonics? Earths major geological features can be attributed to plate tectonics, which gradually remakes our surface. Venus does not appear to have plate tectonics, but its entire surface seems to have been repaved 750 million years ago. Slide 13 Why is Venus so hot? Slide 14 Venus Atmosphere What is it made of? How does it change in height? How does it circulate? Slide 15 Atmosphere of Venus Venus has a very thick carbon dioxide atmosphere with a surface pressure 90 times that of Earth. Venus has a very thick carbon dioxide atmosphere with a surface pressure 90 times that of Earth. Slide 16 Atmosphere of Venus Reflective clouds contain droplets of sulfuric acid. Reflective clouds contain droplets of sulfuric acid. The upper atmosphere has fast winds that remain unexplained. The upper atmosphere has fast winds that remain unexplained. Slide 17 Venus Atmosphere Slide 18 Slide 19 Water condenses into clouds, allowing for rain around 0 C Suns UV light disassociates H 2 0 at this height! Slide 20 Greenhouse Effect on Venus Thick carbon dioxide atmosphere produces an extremely strong greenhouse effect. Thick carbon dioxide atmosphere produces an extremely strong greenhouse effect. Earth escapes this fate because most of its carbon and water are in rocks and oceans. Earth escapes this fate because most of its carbon and water are in rocks and oceans. Slide 21 Why is Venus so hot? The greenhouse effect on Venus keeps its surface temperature at 470C. But why is the greenhouse effect on Venus so much stronger than on Earth? Slide 22 Explaining Venus Atmosphere Lots of Volcanoes CO 2, H2S0 4 are outgassed CO 2 traps infrared heat from Sun Atmosphere heats up Water cant condense => No Rain! Slide 23 Runaway Greenhouse Effect The runaway greenhouse effect would account for why Venus has so little water. The runaway greenhouse effect would account for why Venus has so little water. Greater heat, more evaporation More evaporation, stronger greenhouse effect Slide 24 Thought Question What is the main reason why Venus is hotter than Earth? A. Venus is closer to the Sun than Earth. B. Venus is more reflective than Earth. C. Venus is less reflective than Earth. D. The greenhouse effect is much stronger on Venus than on Earth. E. Human activity has led to declining temperatures on Earth. Slide 25 Thought Question What is the main reason why Venus is hotter than Earth? A. Venus is closer to the Sun than Earth. B. Venus is more reflective than Earth. C. Venus is less reflective than Earth. D. The greenhouse effect is much stronger on Venus than on Earth. E. Human activity has led to declining temperatures on Earth. Slide 26 Carbon Dioxide Cycle Recycle CO2 from atmosphere to crust to atmosphere over time Estimate ~25 million years or more for this to occur on Earth Slide 27 Carbon Dioxide Cycle How do atmospheres of Venus & Mars differ in their ability to cycle CO2 from atmosphere to crust and back?? Slide 28 Carbon Dioxide Cycle Assume all 3 planets had similar compositions and conditions early in the solar systems history Assume all 3 had liquid water, active volcanoes, and CO 2 in atmosphere Slide 29 Carbon Dioxide Cycle Carbon Dioxide Cycle Step 1: Evaporation/Rain Liquid water evaporates Liquid water evaporates Condenses into clouds in lower atmosphere Condenses into clouds in lower atmosphere Rain falls through atmosphere forming Carbonic Acid (H 2 CO 3) Rain falls through atmosphere forming Carbonic Acid (H 2 CO 3) CO2 gas is absorbed 1 Slide 30 Carbon Dioxide Cycle Carbon Dioxide Cycle Step 2: Mineral Erosion by Acid Rain Carbonic Acid (H 2 CO 3) in rivers erodes rocks Carbonic Acid (H 2 CO 3) in rivers erodes rocks Carbonate (CO 3 2- ) ion picked up in minerals washed to ocean Carbonate (CO 3 2- ) ion picked up in minerals washed to ocean Calcium easily absorbed Calcium easily absorbed CO2 is carried to oceans 2 Slide 31 Carbon Dioxide Cycle Carbon Dioxide Cycle Step 3: Tying Carbon into Rocks & Life! Calcium from rocks forms CaCO 3 (Calcium Carbonate) Calcium from rocks forms CaCO 3 (Calcium Carbonate) CaCO 3 = Limestone CaCO 3 = Limestone CaCO 3 = Coral, Mollusk shells! CaCO 3 = Coral, Mollusk shells! 3 CO2 accumulates on seafloor Slide 32 Carbon Dioxide Cycle Carbon Dioxide Cycle Step 4: Tectonics & Subduction! Tectonics gradually pulls seafloor down Tectonics gradually pulls seafloor down CaCO 3 broken back into CO2 & other minerals CaCO 3 broken back into CO2 & other minerals 4 CO2 now inside crust Slide 33 Carbon Dioxide Cycle Carbon Dioxide Cycle Step 5: Volcanic Outgassing! Eventual Volcanic Activity pushes CO2 back into atmosphere Eventual Volcanic Activity pushes CO2 back into atmosphere 5 CO2 now in atmosphere again! Slide 34 1 Too Hot for clouds to form low enough But Volcanoes dont stop! Carbon Dioxide Cycle Carbon Dioxide Cycle Venus Feedback Loop Failure 5 Slide 35 No Rain No Rain NO CO2 gas absorbed NO CO2 gas absorbed More CO2 added! More CO2 added! Runaway Greenhouse Effect! Runaway Greenhouse Effect! 1 Carbon Dioxide Cycle Carbon Dioxide Cycle Venus Feedback Loop Failure Slide 36 Carbon Dioxide Cycle Carbon Dioxide Cycle Mars Feedback Loop Failure Evaporation Evaporation Rain Rain CO2 gas flushed out CO2 gas flushed outBut Interior cools off Interior cools off Volcanoes Stop! Volcanoes Stop! 1 5 Slide 37 Carbon Dioxide Cycle Carbon Dioxide Cycle Mars Feedback Loop Failure Atmosphere CO2 decreases Atmosphere CO2 decreases Planet freezes Planet freezes 1 5 Slide 38 Mars Mars Slide 39 Schiaparellis Canals Slide 40 Slide 41 Slide 42 Pyramids Happy Faces! More illusions : Slide 43 A Martian Sunset Slide 44 Mars vs. Earth 50% Earths radius, 10% Earths mass 50% Earths radius, 10% Earths mass 1.5 AU from the Sun 1.5 AU from the Sun Axis tilt about the same as Earth Axis tilt about the same as Earth Similar rotation period (25 hours/day) Similar rotation period (25 hours/day) Thin CO 2 atmosphere: little greenhouse effect Thin CO 2 atmosphere: little greenhouse effect =>Main difference: Mars is SMALLER Slide 45 Seasons on Mars Seasons on Mars are more extreme in the southern hemisphere because of its elliptical orbit. Seasons on Mars are more extreme in the southern hemisphere because of its elliptical orbit. Slide 46 Slide 47 Storms on Mars Seasonal winds on Mars can drive huge dust storms. Seasonal winds on Mars can drive huge dust storms. Slide 48 What geological features tell us water once flowed on Mars? Slide 49 The surface of Mars appears to have ancient riverbeds. Slide 50 The condition of craters indicates surface history. Eroded crater Slide 51 Close-up of eroded crater Slide 52 The Martian Surface Map Slide 53 Slide 54 Volcanoesas recent as 180 million years ago Slide 55 Past tectonic activity Slide 56 A *really* GRAND canyon Slide 57 A *even bigger* volcano Slide 58 Slide 59 Differences in Hemispheres Slide 60 Low-lying regions may once have had oceans. Slide 61 Slide 62 Opportunity Spirit NASAs SPIRIT & OPPORTUNITY Roversstill sending data! Slide 63 2004 Opportunity Rover provided strong evidence for abundant liquid water on Mars in the distant past. How could Mars have been warmer and wetter in the past? Slide 64 Today, most water lies frozen underground (blue regions) Some scientists believe accumulated snowpack melts carve gullies even today. Slide 65 Why did Mars change? Slide 66 Climate Change on Mars No widespread surface water for 3 billion years. No widespread surface water for 3 billion years. Greenhouse effect probably kept surface warmer before. Greenhouse effect probably kept surface warmer before. Somehow Mars lost most of its atmosphere. Somehow Mars lost most of its atmosphere. Slide 67 Climate Change on Mars Magnetic field may have preserved early Martian atmosphere. Magnetic field may have preserved early Martian atmosphere. Solar wind may have stripped atmosphere after field decreased because of interior cooling. Solar wind may have stripped atmosphere after field decreased because of interior cooling. Slide 68 Polar Climate Change Slide 69 Exploring Mars Slide 70 Winds on Mars Slide 71 Wind trails from dust devils Slide 72 Rivers on Mars & Earth! Slide 73 Slide 74 Slide 75 Slide 76 Slide 77 Slide 78 More evidence of water Slide 79 Slide 80