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Chapter 7 Earth and the Terrestrial Worlds. Why is Venus so hot?

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Presentation on theme: "Chapter 7 Earth and the Terrestrial Worlds. Why is Venus so hot?"— Presentation transcript:

1 Chapter 7 Earth and the Terrestrial Worlds

2 Why is Venus so hot?

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.

4 Venus in UV light

5 Venus mapped with Radar

6 The surface of Venus

7 Venus’ surface Venera Probes from 1970’s survived for minutes…

8 Venus’ surface Venera Probes from 1970’s survived for minutes…

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12 Does Venus have plate tectonics? Earth’s 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.

13 Why is Venus so hot?

14 Venus’ Atmosphere What is it made of? How does it change in height? How does it circulate?

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.

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.

17 Venus’ Atmosphere

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19 Water condenses into clouds, allowing for rain around 0 C Sun’s UV light disassociates H 2 0 at this height!

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.

21 Why is Venus so hot? The greenhouse effect on Venus keeps its surface temperature at 470°C. But why is the greenhouse effect on Venus so much stronger than on Earth?

22 Explaining Venus’ Atmosphere Lots of Volcanoes CO 2, H2S0 4 are outgassed CO 2 traps infrared heat from Sun Atmosphere heats up Water can’t condense => No Rain!

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

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.

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.

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

27 Carbon Dioxide Cycle How do atmospheres of Venus & Mars differ in their ability to cycle CO2 from atmosphere to crust and back??

28 Carbon Dioxide Cycle Assume all 3 planets had similar compositions and conditions “early” in the solar system’s history… Assume all 3 had liquid water, active volcanoes, and CO 2 in atmosphere

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

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

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

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

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!

34 1 Too Hot for clouds to form low enough But… Volcanoes don’t stop! Carbon Dioxide Cycle Carbon Dioxide Cycle Venus Feedback Loop Failure 5

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

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

37 Carbon Dioxide Cycle Carbon Dioxide Cycle Mars Feedback Loop Failure Atmosphere CO2 decreases Atmosphere CO2 decreases Planet freezes Planet freezes 1 5

38 Mars Mars

39 Schiaparelli’s “Canals”

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42 Pyramids Happy Faces! More illusions :

43 A Martian Sunset…

44 Mars vs. Earth 50% Earth’s radius, 10% Earth’s mass 50% Earth’s radius, 10% Earth’s 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

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.

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47 Storms on Mars Seasonal winds on Mars can drive huge dust storms. Seasonal winds on Mars can drive huge dust storms.

48 What geological features tell us water once flowed on Mars?

49 The surface of Mars appears to have ancient riverbeds.

50 The condition of craters indicates surface history. Eroded crater

51 Close-up of eroded crater

52 The Martian Surface Map

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54 Volcanoes…as recent as 180 million years ago…

55 Past tectonic activity…

56 A *really* GRAND canyon…

57 A *even bigger* volcano

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59 Differences in Hemispheres

60 Low-lying regions may once have had oceans.

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62 Opportunity Spirit NASA’s SPIRIT & OPPORTUNITY Rovers…still sending data!

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?

64 Today, most water lies frozen underground (blue regions) Some scientists believe accumulated snowpack melts carve gullies even today.

65 Why did Mars change?

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.

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.

68 Polar Climate Change

69 Exploring Mars

70 Winds on Mars

71 Wind trails from “dust devils”

72 Rivers on Mars … & Earth!

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78 … More evidence of water

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