Venus Astronomy 311 Professor Lee Carkner Lecture 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 --  km –  km –  0-30 km –  Temperature:  Pressure:   90 atmospheres at surface

Temperature in Atmosphere

Formation of Atmosphere 1) Early Venus heats up, water evaporates 2) 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

Interlude Planetary 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 CO 2 with sulfuric acid clouds  Thick (90 atmospheres) :  No water to wash out CO 2  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