venus astronomy 311 professor lee carkner lecture 11
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Venus
Astronomy 311Professor Lee
CarknerLecture 11
Why does Mercury have 3-2 spin orbit coupling instead of 1-1?
a) Because of the Caloris impactb) Due to resonance with Venusc) Because of its large iron cored) Because it is not quite close enough to
the sune) Because of the relatively high
eccentricity of its orbit
Why do we think there might be water ice at Mercury’s poles?
a) Radar reflects strongly off of polar regions
b) We see the spectroscopic signature of hydrogen
c) The Caloris impactor should have lowered temperatures at the poles enough for ice to form
d) There is evidence of comet impacts at the poles
e) The slow rotation of Mercury is ideal for ice formation
Venus -- The Goddess of Beauty
Romans named it Venus for its beauty symbol for Venus
is a mirror
Venus from Earth
sometimes called the morning or
evening “star” Venus is covered with clouds
clouds reflect ~75% of sunlight
Venus Facts
Size: 95% Earth
Orbit: 0.7 AU
Description: Earth-sized, hot, thick atmosphere (Earth’s evil twin)
Venus’s Retrograde Rotation
When viewed from above the north pole of the Earth, most of the planets: revolve around the Sun counterclockwise
It is upside down
Why is Venus upside down?
We have no evidence of this, however
Retrograde Rotation
Rotation Rate
Venus revolves around the Sun with a period of 225 days
Reason is unclear
impact altered its rotation rate?
Venus from Pioneer
Venus’s Atmosphere
Composition:
Pressure: 90 atmospheres (equal to being 1 km underwater on Earth)
Temperature: 750 K (hottest planet in solar system)
Chemicals in Atmosphere Forms many sulfur compounds including
sulfuric acid (H2SO4) Sulfuric acid has vapor point such that it
boils on the surface but condenses in the atmosphere to form clouds
Also, hydrofluoric acid (HF), hydrochloric acid (HCl) and other corrosive compounds
Temperature in Atmosphere
Formation of Atmosphere1)
2) Water produces greenhouse effect, boils oceans3)
4) With no water, CO2 cannot be removed from atmosphere, thick CO2 atmosphere forms
5)
6) Volcanoes outgas sulfur, forms sulfuric acid clouds
The Surface of Venus
Clouds block blue light so surface appears red, but surface is actually gray
Chemical analysis indicates that
surface rocks are similar to basalt, a volcanic rock
InterludePlanetary Configurations
Magellan Maps Venus
Probes and landers saw only bits and pieces of it
Used radar to penetrate the clouds and map the surface with a resolution of 100 meters
Radar Map of Venus
Global Surface of Venus
Two large highlands or continents (Aphrodite Terra and Ishtar Terra)
The entire surface is the same age
Venus re-surfaces itself
Surface features named after women
Volcanism on Venus
Evidence for Volcanism: sulfur in atmosphere filled craters
Note that volcanoes are not active now
The Interior of Venus With so much volcanism, part of Venus
must be molten, but:
the crust is not broken up into moving plates
Why no plate tectonics? too hot or too dry?
Venus probably has a molten core
Next Time
Read Chapter 7
Summary
Earth-Sized, hot, thick atmosphere (Earth’s evil twin)
Rotates slowly and upside-down Studied by Venera landers and
Magellan radar mapper
Summary: Atmosphere
Composed of CO2 with sulfuric acid clouds
Thick (90 atmospheres) : No water to wash out CO2
Hot (750 K): Powerful greenhouse effect
Summary: Surface
Volcanism shapes surface and outgases sulfur See volcanoes and lava flow channels
Surface mostly flat with a few highlands
Nature of core is unknown