Venus
Astronomy 311Professor Lee
CarknerLecture 11
Venus -- The Goddess of Beauty
Venus is one of the brightest planets in the sky
Venus from Earth
Venus is only seen near the Sun
Venus shows phases Venus is covered with clouds
Venus Facts
Size: 95% Earth
Orbit: 0.7 AU
Description:
Venus’s Retrograde Rotation
When viewed from above the north pole of the Earth, most of the planets:
Venus rotates clockwise
Why is Venus upside down?
We have no evidence of this, however
Retrograde Rotation
Rotation Rate
Venus rotates on its axis with a period of 243 days
Day is longer than a year Reason is unclear
Venus from Pioneer
Venus’s Atmosphere In the 1960’s and 1970’s probes were
dropped into Venus’s atmosphere Composition:
Pressure: Temperature: 750 K (hottest planet in
solar system)
Chemicals in Atmosphere A lot of sulfur in atmosphere 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
Structure of Atmosphere
68 km and up --
48-68 km –
30-40 km –
0-30 km –
Temperature:
Pressure:
90 atmospheres at surface
Temperature in Atmosphere
Formation of Atmosphere1) Early Venus heats up, water evaporates2)
3) Ultraviolet light disassociates water and destroys it
4)
5)
6) Volcanoes outgas sulfur, forms sulfuric acid clouds
Venera 13 Mock-up
Venera 13 on Venus
The Surface of Venus
Chemical analysis indicates that
surface rocks are similar to basalt, a volcanic rock
InterludePlanetary Configurations
Magellan Maps Venus
Venus’s atmosphere is so thick that you cannot see the surface from orbit
Our map of Venus comes from the
Magellan spacecraft (1990)
Radar Map of Venus
Global Surface of Venus Surface is generally level (smoothed
by lava) Many volcanoes and lava features The entire surface is the same age
Surface features named after
women
Gula Mons
Vires-Akka Chasma
Alcott Crater
A Corona
Lava Domes
The Highlands of Aphrodite Terra
Danu Mountains
Wind Blown Streak
Sif Mons
Volcanism on Venus
Evidence for Volcanism: smoothed surface lava channels visible shield features
The Interior of Venus
No plate tectonics moving lava disturbs the crust enough to
produce a few mountains and highlands
too hot or too dry?
Venus probably has a molten core
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