Photo of aurora in Wisconsin by Chris Ven Haus

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Photo of aurora in Wisconsin by Chris Ven Haus
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Solar System Planets Venus
I. Venus - Radar Exploration - Surface
Features - Atmosphere
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Further Spacecraft Exploration of Venus
Galileo en route to Jupiter, took an orbital
path flyby of Venus in 1990 Images in the
infrared and UV show cloud patterns, layers,
structure Magellan NASAs Venus Orbiter
extensive radar systems for surface
studies Launch of Shuttle in May 1989 Plunged
into thick atmosphere in 1994
Radar Map of Venus
Magellan deployed from Shuttle
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Cartoon of Magellan orbiting/imaging Venuss
surface Radar Friday Surface features on Venus
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Properties of Venus atmosphere determined by
spacecraft

• dry, hot world! temperatures
• constant at T700 K
• incredibly high pressures at
• Venus surface 90 times greater
• than average sea level air!
• similar to pressures 1 km below
• the ocean (think scuba diving)
• T so high because atmosphere is
• largely CO2 and the greenhouse
• effect is incredibly effective (much
• more so than on Earth) runaway!
• On Earth, CO2 is only 1 of
• atmosphere...keeps us warm, but
• not HOT!

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Venus atmosphere has several layers and haze

• - American, Soviet spacecraft carried instruments
  to study T, Pressure of atmosphere
• They studied atmospheric properties as a
  function of height in the atmosphere
• Pressure and Temperature increase as you go into
  the atmosphere, toward surface

Clouds are contained within a layering
between 40-80 km above Venus surface
Remarkably clear of clouds between 30 km and the
surface, but high pressure!!
At 50 km above Venus surface, the
atmospheric pressure is same as Earths!
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• Composition/Nature of Venus atmosphere
• Sulfur combines to form sulfur dioxide,
  hydrogen sulfide, sulfuric acid
• Venus atmosphere composed of droplets of
  sulfuric acid, but they never reach
• surface of Venus
• Atmosphere is a caldron of chemical reactions,
  hostile to metals and other solids
• Circulation in Venus atmosphere unusual
  different than Earths

virga are raindrops on Earth that evaporate
before reaching the ground
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• Circulation of Venus atmosphere
• energy in the atmosphere comes from absorbed
  sunlight similar to the Earth
• upper levels of atmosphere rotate fastest
  complete one rotation in just 4 days
• contrast slow rotation of planet (243 days)
  and fast rotation of atmosphere
• convection occurs in the atmospheric layers (hot
  rising, cool falling)
• fast wind speeds in atmosphere (350 km/hr)
  compared to surface (5 km/hr)

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What is the origin of Venus thick atmosphere?

• Volcanoes on Earth (like Earths Mt. St. Helens)
  inject significant amounts of SO2 and H2S and
  H2SO4 into the Earths atmosphere
• Because of Venuss thick atmosphere, we have no
  direct observations of volcanoes on Venus
• We can infer that volcanoes exist on Venus
• spacecraft probes measure high levels of sulfur
  compounds (volcanic in origin)
• radio antennas detected bursts of radio waves
  similar to signals detected from Earth volcanoes
• RADAR measurements of Venus surface reveal
  images of volcanoes

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Radar Images of Venus reveal several large
volcanoes

• Magellan images
• microwave RADAR images
• dark areas smooth surface
• where reflection is weak
• bright areas rough surface
• which reflects microwaves
• - bright lava flows extend
• from caldera - lava rough
• large volcanoes on Venus
• Sapas Mons
• Theia Mons
• Maat Mons

Sapas Mons 1.5 km high
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Radar Images can be used to reconstruct surface
of Venus

• use radar in combination with a laser altimeter
• can get height of features from laser altimeter,
  surface type from radar

• Computer-generated
• reconstruction of a
• tall volcano, crater
• impacts and large
• plains on Venus surface
• False color added
• to reflect what sunlight
• may look like as it passes
• through Venus thick
• clouds

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• MOST volcanoes on Venus
• are probably inactive now
• (similar to Earth)
• How do we tell the AGE of
• the volcanic activity??
• - radar reflectivity
• - bright rough lava
• - dark smooth surfaces
• Estimations are that overall surface
• lava is only 100 million yrs old (much younger
  than Moon, Mercury surfaces)
• but Magellan has revealed a few places
• (e.g., Maat Mons) 10 million yrs old.

Magellan image of volcanoes and lava flows
? Need to verify volcanic activity, surface
features by looking at samples, images directly
from the surface!
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Soviet Venera spacecraft landed 10 times on Venus!

• spacecraft landed on Venusian surface sent back
  data for 23 min 120 min
• TV cameras and other instruments reveal that
  surface is rocky with basalt-type
• rocks (lava) surface covered with a thin lava
  crust which fractured upon cooling

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Volcanoes play an important role in understanding
Venus atmosphere

• Similarities between Venus and Earth
• with respect to atmospheres and volcanoes
• - original atmosphere originated from
• outgassing of volcanoes (CO2, H2O, SO2 gasses)
• - volcanoes on both planets have during their
• history replenished the thick atmospheres
• Differences between Venus and Earth
• with respect to atmospheres and volcanoes
• - Earth has abundant water (oceans), little CO2
• - Venus has no water, but thick CO2 atmosphere

How did Earth lose its CO2 and how did Venus lose
its water??