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Venus and Mars

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					   Venus and Mars




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              Venus and Mars




              Two most similar planets to Earth:
• Similar in size and mass           • Atmosphere
• Same part of the solar system      • Similar interior structure

             Yet, no life possible on either one of them.
                           Venus
             The Rotation of Venus
  Almost all planets rotate
 counterclockwise, i.e. in the
same sense as orbital motion.

        Exceptions:
 Venus, Uranus and Pluto

 Venus rotates clockwise,
 with period slightly longer
    than orbital period.

     Possible reason:

  • Off-center collision with
    massive protoplanet
         The Atmosphere of Venus




                                        4 thick cloud layers (→ surface
                      UV image             invisible to us from Earth).
                                     Very stable circulation patterns with
  Extremely inhospitable:
                                     high-speed winds (up to 240 km/h)
   96 % carbon dioxide (CO2)
   3.5 % nitrogen (N2)
Rest: water (H2O), hydrochloric
acid (HCl), hydrofluoric acid (HF)
     Given that Venus’ atmosphere consists almost
     entirely of CO2, what would you expect for the
     temperature on the surface of Venus?
                                                                                                            :10
1.     Very cold because no
       light reaches the surface.
2.     Moderately warm, similar
       to Earth
3.     Very hot because of a
       very efficient greenhouse
       effect.
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         The Atmosphere of Venus




                                        4 thick cloud layers (→ surface
                      UV image             invisible to us from Earth).
                                     Very stable circulation patterns with
  Extremely inhospitable:
                                     high-speed winds (up to 240 km/h)
   96 % carbon dioxide (CO2)
   3.5 % nitrogen (N2)                   Very efficient “greenhouse”!
Rest: water (H2O), hydrochloric      Extremely high surface temperature
acid (HCl), hydrofluoric acid (HF)         up to 745 K (= 880 oF)
      Would you expect to find many impact
       craters on Venus (like on Mercury)?
                                                                                                                    :10
1.         Yes; even more because Venus
           is more massive.
2.         Yes, just about as many as on                               25%          25%                  25%        25%
           Mercury.
3.         No, because there have been
           much fewer meteorites than
           near the orbit of Mercury.
4.         No, because Venus is protected
           from meteorite impacts by its
           dense atmosphere.
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               The Surface of Venus
          Early radar images already revealed mountains, plains, craters.

                   More details from orbiting and landing spacecraft:

     Venera 13
  photograph of
 surface of Venus:

 Colors modified by
  clouds in Venus’
    atmosphere


After correction for
atmospheric color
       effect:
   Radar Map of Venus’ Surface

Surface features
shown in artificial
     colors.

• Scattered impact
      craters

• Volcanic regions

• Smooth lava flows
                 Lava Flows




   Young, uneven lava flows (shown: Lava flow near
Flagstaff, AZ) show up as bright regions on radar maps.
    Surface Features on Venus




                     Highland regions:
Smooth lowlands
                  Maxwell Montes are ~ 50 %
                   higher than Mt. Everest!
               Craters on Venus
  Nearly 1000 impact
   craters on Venus’
        surface:
    → Surface not
      very old.
   No water on the
    surface; thick,
  dense atmosphere
    → No erosion

→ Craters appear sharp
      and fresh
All volcanoes on Venus are …                                                                                :10


 1. Subduction-zone                                                       50%                     50%
    volcanoes.
 2. Shield volcanoes.


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                     Shield Volcanoes


  Found above
   hot spots:



   Fluid magma
  chamber, from
 which lava erupts
repeatedly through
  surface layers
      above.



      All volcanoes on Venus and Mars are shield volcanoes
       Volcanism on Venus
                       Sapas Mons (radar image)




~ 400 km (250 miles)                2 lava-filled calderas
                       Lava flows
Volcanic Features
    on Venus




                                                             Aine Corona

                                      Coronae: Circular bulges formed by
Baltis Vallis: 6800 km long                    volcanic activity
lava flow channel (longest
   in the solar system!)
        Lava flows
                              Pancake Domes:
     Some lava flows
                               Associated with
  collapsed after molten
                               volcanic activity
    lava drained away
                              forming coronae
  The collapsed lava flows on Venus are very                                                                            :10
similar to which surface features on the Moon?

 1.     Long rays of ejecta from
                                                                   20%           20%         20%           20%          20%
        impact craters.
 2.     Lobate Scarps.
 3.     Sinous Rilles.
 4.     Maria.
 5.     Large mountain ridges.
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Lunar Highlands
 and Lowlands
     Sinous rilles =
   remains of ancient
       lava flows.

   May have been lava
    tubes which later
    collapsed due to
        meteoride
     bombardment.



       Apollo 15 landing site
          Lakshmi Planum and
           Maxwell Mountains
                                                    Radar image




Wrinkled mountain formations indicate compression and wrinkling,
    though there is no evidence of plate tectonics on Venus.
Simulated flights over the surface of Venus
                  A History of Venus
                  Complicated history; still poorly understood.
           Very similar to Earth in mass, size, composition, density,
                    but no magnetic field → Core solid?

  → Solar wind interacts
     directly with the
atmosphere, forming a bow
 shock and a long ion tail.
           What makes soda drinks bubble?
1.         The heat in the drink evaporates
           water, which rises up in bubbles.
2.         Gases given off by the breathing                                               :10
           of bacteria in the drink.                                    20%         20%         20%        20%        20%
3.         Oxygen (O2) dissolved in the
           water.
4.         Sulfur dioxide (SO2) dissolved in
           the water (forming Sulfurous Acid,
           H2SO3).
5.         Carbon dioxide (CO2) dissolved in
           the water (forming Carbonic Acid,
           H2CO3).
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                                                                         1            2           3         4           5
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                  A History of Venus
                  Complicated history; still poorly understood.
           Very similar to Earth in mass, size, composition, density,
                    but no magnetic field → Core solid?

  → Solar wind interacts
     directly with the
atmosphere, forming a bow
 shock and a long ion tail.
    CO2 produced during
   outgassing remained in
   atmosphere (on Earth:
     dissolved in water).

   Any water present on the
 surface rapidly evaporated →
feedback through enhancement
      of greenhouse effect
                                     Mars
• Diameter ≈ ½ Earth’s diameter

• Very thin atmosphere, mostly CO2
• Rotation period = 24 h, 40 min.
• Axis tilted against orbital plane by 25o,
   similar to Earth’s inclination (23.5o)
• Seasons similar to Earth → Growth
    and shrinking of polar ice cap

• Crust not broken into tectonic plates

• Volcanic activity (including highest
    volcano in the solar system)
         The Atmosphere of Mars
   Very thin: Only 1 % of
pressure on Earth’s surface

        95 % CO2

     Even thin Marsian
    atmosphere evident
 through haze and clouds
    covering the planet

 Occasionally: Strong dust
 storms that can enshroud
     the entire planet.
                        What is rust?                                                           :10

1.         Silicon dioxide (SiO2)
2.         Hydrogen oxide (H2O)                                   20%         20%         20%        20%        20%

3.         Aluminum (Al)
4.         Iron oxide (FeO)
5.         Carbon dioxide (CO2)

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The Atmosphere of Mars (II)
  Most of the Oxygen bound in oxides in rocks

        → Reddish color of the surface
Which of the following gasses is the heaviest?

 1.         Oxygen (O2)                                                                :10
 2.         Hydrogen (H2)
                                                                   20%         20%         20%        20%        20%
 3.         Helium (He)
 4.         Carbon dioxide (CO2)
 5.         Water vapor (H2O)


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  History of Mars’ Atmosphere
        Initial atmosphere from outgassing.


   Small mass of Mars;
  moderate temperatures

     Lighter gasses:
 Molecule velocity greater
 than escape velocity: →
gasses escape into space.


             Mars has lost all lighter gasses;
           retained only heavier gasses (CO2).
Please press “1” to check your transmitter.
  History of Mars’ Atmosphere
        Initial atmosphere from outgassing.


   Small mass of Mars;
  moderate temperatures

     Lighter gasses:
 Molecule velocity greater
 than escape velocity: →
gasses escape into space.


             Mars has lost all lighter gasses;
           retained only heavier gasses (CO2).
The Atmospheric Temperature Structures
       of the Terrestrial Planets
Why would the surface of Venus be colder than
  Earth’s if here was no greenhouse effect?
1.        Because of its longer day/night
          cycle.                                                                          :10
2.        Because of Venus’ dense cloud                                     25%          25%                 25%        25%
          cover that reflects most of the
          sunlight.
3.        Because Venus is further away
          from the sun than Earth.
4.        Because of its retrograde rotation.
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Why do the atmospheres of Venus
and Mars not have the temperature
 “bump” that we see in the Earth’s
          stratosphere?
                               :10
1.         Because Venus and Mars don’t have
           an ozone layer.
2.         Because on Venus and Mars, there’s
           no greenhouse effect active.
3.         Because X-rays are not absorbed in
           the atmospheres of Venus and Mars.
4.         Because visible light does not                                           25%         25%        25%    25%
           penetrate the atmospheres of Venus
           and Mars.
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            The Geology of Mars
      Giant volcanoes

           Valleys

       Impact craters



Reddish deserts of broken
rock, probably smashed by
    meteorite impacts.

                            Vallis Marineris
              Geology of Mars (II)
Northern Lowlands: Free of craters; probably     Possibly once
    re-surfaced a few billion years ago.       filled with water.




         Southern Highlands: Heavily cratered; probably
                     2 – 3 billion years old.
               Volcanism on Mars
 Volcanoes on
 Mars are shield
  volcanoes.



Olympus Mons:

   Highest and
 largest volcano
   in the solar
     system:
Height = 27 km!
           What is the elevation of Mt. Everest?
1.     2,512 m.
                                                              20%         20%             20%            20%            20%
2.     5,136 m.
                                         :10
3.     8,868 m.
4.     15,925 m.
5.     21,856 m.

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 Why are the highest volcanoes on Mars much
 higher than the highest mountains on Earth?
1.         They are better fed by Mars’
           caramel interior.                                                              :10
2.         Mars provides a weaker gravity
           that would resist the build-up of                                 25%         25%         25%           25%
           mountains.
3.         There is no erosion on the
           surface of Mars.
4.         Subduction zones on Mars are
           much more violent than on Earth.
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         Volcanism on Mars (II)
   Tharsis rise
 (volcanic bulge):

 Nearly as large as
     the U.S.

Rises ~ 10 km above
mean radius of Mars.

 Rising magma has
 repeatedly broken
  through crust to
  form volcanoes.
             Hidden Water on Mars
  No liquid water on the surface:
Would evaporate due to low pressure.
But evidence for liquid water in the past:
 Outflow channels from sudden,
         massive floods
    Collapsed structures after
 withdrawal of sub-surface water
        Valleys resembling
       meandering river beds

  Gullies, possibly from debris flows

     Central channel in a valley
  suggests long-term flowing water
Hidden Water on Mars (II)




     Gusev Crater and Ma’adim Vallis:

 Giant lakes might have drained repeatedly
 through the Ma’adim Vallis into the crater.
    Evidence for Water on Mars




          Galle,
 the “happy face crater”            Meteorite ALH84001:
                               Identified as ancient rock from Mars.
                              Some minerals in this meteorite were
Large impacts may have      deposited in water → Martian crust must
ejected rocks into space.   have been richer in water than it is today.
Ice in the Polar Cap
           Polar cap contains
            mostly CO2 ice,
            but also water.


           Multiple ice regions
          separated by valleys
               free of ice.




                Boundaries of polar
                caps reveal multiple
                  layers of dust, left
                behind by repeated
                 growth and melting
                of polar-cap regions.
 Could you, in principle, go skiing
  on the CO2 ice caps of Mars?                                                                        :10

1.     Yes. CO2 ice is just as
                                                                         50%                     50%
       slippery as water ice.
2.     No. CO2 ice is not
       slippery like water ice.


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              The Moons of Mars
                                      Two small moons: Phobos
                                       (diameter ~ 25 km) and
                                      Deimos (diameter = 12 km).

                                       Too small to pull themselves
                                          into spherical shape.

                                      Typical of small, rocky bodies:
                                         Dark grey, low density.

      Phobos
  Very close to Mars; orbits around
   Mars faster than Mars’ rotation.


Probably captured from outer asteroid belt.
                                                          Deimos
  Since Mars’ Moons are orbiting the planet faster
than Mars’ rate of rotation, an observer on Mars will                                                         :10
   see the moons rise in the … and set in the …!
1.       North, South.
2.       South, North.                                               20%         20%         20%        20%         20%
3.       East, West.
4.       West, East.
5.       Not at all. They will always
         be up or always be down.

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  101    102   103   104   105   106   107   108   109   110   111   112   113   114   115   116




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