Venus

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