Lecture 18: Venus- Planet of Love and Sulfuric Acid Rain

"Abandon hope, all ye who enter here."
Dante, The Inferno

Navigation Options

You may :

Go to the Astro 105 Main Menu

Go to the Class Schedule

Look at the Review Questions for Lecture # 18

Go to the Lecture # 17 Master Page

Go to the Lecture # 19 Master Page

Date: November 11, 1994
Reading Assignment: pp. 217-240

Description : introduction to the geology, atmosphere and characteristics of Venus

Objectives

Understand the characteristics of the current atmosphere.

Be able to describe the atmosphere of Venus.

Be able to explain why Venus is so hot.

Be able to explain why Venus has almost no water vapor.

Be able to explain why the atmosphere of Venus is so different from Earth.

Be able to describe the main surface features of Venuse.

Be able to describe why we believe Venus has active volcanos.

Lecture Outline

Slide # 1: Lecture 18: Venus- Planet of Love (and Sulfuric Acid Rain)

Slide # 2: Venus

orbit and rotation

composition and internal structure

surface features and history

atmosphere

magnetosphere

Slide # 3: Planetary Structure

core

mantle

crust

hydrosphere

atmosphere

magnetosphere

Slide # 4: Terrestrial Planets and Moons

smaller planets and moons

Slide # 5: Planetary Orbits

inner solar system

Slide # 6: Moons

Mercury, Venus - none

Earth - 1

Mars - 2

Jupiter - 16

Saturn - 18

Uranus - 15

Neptune - 8

Pluto - 1

Slide # 7: Planetary Masses

Mercury = 1/20

Venus = 4/5

Earth = 1

Mars = 1/9

Jupiter = 318

Saturn = 95

Uranus = 15

Neptune = 17

Pluto = 0.002

Slide # 8: Venus- Revolution

semimajor axis = 0.72 AU

very circular orbit

orbital period = 225 days

Slide # 9: Venus Seen from Earth

Venus can never be more than 47 degrees from the Sun

Slide # 10: Venus Seen from Earth

Orbital Configurations

Slide # 11: VenusÕs Rotation

surface of Venus is obscured by clouds

radar measurements detect a sidereal rotation period of 243 days

one solar day on Venus is 117 Earth days

Slide # 12: VenusÕs Rotation

slow retrograde rotation

Slide # 13: Tidal Resonance?

117 day solar day MAY be a 5:1 spin-orbit resonance with Earth

orbital timings indicate this is probably a coincidence

Slide # 14: Atmospheric Composition of Venus

carbon dioxide (96.5%)

nitrogen (3%)

traces of other gases

sulfur dioxide (0.015%)

water vapor (0.01%)

argon (0.007%)

atmospheric pressure = 90 x atmosphere of Earth

Slide # 15: Atmosphere of Venus

structure of the atmosphere

Slide # 16: Where is the H2O?

all water is in vapor form

much less water than on Earth in vapor or in the oceans

where did the water go?

Slide # 17: Carbon Dioxide

much more CO2 in the atmosphere than in EarthÕs atmosphere

total amount of CO2 (including CO2 inside Earth rocks) is about the same on th

Slide # 18: Missing Water Diagram

very little water survives in the atmosphere

none survives on the surface

Slide # 19: Missing Water Vapor

water on Venus is in vapor (gaseous) form

none would be on the surface

water in the upper atmosphere is hit by UV from the Sun

no ozone layer around Venus

UV breaks water into hydrogen and oxygen

hydrogen escapes into space

oxygen becomes bound to rocks

Slide # 20: Atmospheres

molecular speed and escape velocity

Slide # 21: Origin of the Atmospheres

primary atmosphere- Hydrogen and Helium

gases common in the solar system

escaped from Venus

secondary atmosphere

volcanic outgassing

Nitrogen, CO2, sulfur dioxide, water vapor, methane

EarthÕs atmosphere evolved; VenusÕs atmosphere did not evolve

Slide # 22: Surface Heating of Planets

Most planets are warmed mainly by the SunÕs energy

sunlight strikes planetÕs surface and is absorbed

planet warms

planet radiates as a Black-Body

Slide # 23: A Balance Between Radiation and Absorption

energy radiated = energy absorbed

(on average)

Slide # 24: The Temperature of Venus

750K average temperature

no day-night variations

Slide # 25: The Greenhouse Effect

visible light passes through the atmosphere

the light is absorbed by the surface of Venus

Venus warms up and radiates infrared energy

Most of the Infrared Energy is blocked by carbon dioxide

Slide # 26: Greenhouse Gases

Earth and Venus

Slide # 27: VenusÕs Composition

average density = 5.2 gm/cm3

very similar to Earth (5.5 gm/cm3)

similar mass (82% of EarthÕs)

the size of the core about the same as EarthÕs core

Slide # 28: Exploration of Venus

clouds cover the planet

Slide # 29: Views of the Surface

first views of the surfaces used radar from telescopes on the Earth

current maps were made using orbiting satellites which use radar

Slide # 30: Radar

radio pulse is sent from Earth

Slide # 31: Radar

radio wave reflects off the surface

Slide # 32: Radar

the reflection does not arrive at one time

by timing the arrival of the wave on Earth, we can map the planet

Slide # 33: Radar

some energy is immediately reflect at the nearest surface

other parts of the wave reflect from other parts of the planet

the reflections happen at different times

Slide # 34: US Exploration of Venus

Mariner 2, 5 (1962, 1967) 35,000 km flyby

Mariner 10 (1974) 6,000 km flyby

Pioneer Venus (1978)

atmospheric probes

low resolution radar mapping

Magellan 1990

high resolution maps

excellent surface maps

Slide # 35: Soviet Exploration

Venera 4 through Venera 12 (Soviet)

Venera 7 - first soft landing 1970

23 minutes survival time

longest survival time was about 1 hour

Venera 15, 16 - first radar maps of the surface

2 km resolution

Slide # 36: Terrain of Venus

mostly flat plains

80% is flat to 2km

similar to basaltic ocean floor on Earth

2 continent sized features

some volcanos and large mountains

no tectonic activity

Slide # 37: Highlands on Venus

Ishtar Terra

highland in Northern Hemisphere

Aphrodite Terra

surface buckling

Slide # 38: Venus

planetary overview

Slide # 39: Venus

planetary surface

Slide # 40: Volcanos on Venus

volcanic formations

caldera

shield volcanos

cornoae

atmospheric changes

sulfur dioxide

bursts of radio energy

Slide # 41: Volcanic Formations

Alpha Regio - troughs, ridges and faults

Slide # 42: Volcanic Features

troughs, ridges, and faults are associated with volcanic activity

some volcanos and volcanic lavas are found this region

Slide # 43: Volcanic Formations

Corona and Arachnoid

Slide # 44: Volcanic Formations

Corona- circular volcanic structures surrounded by ridges and groves

Arachnoids - circular to ovoid features with concentric rings and complex frac

Corona and Arachnoids form when magma cracks the surface

Slide # 45: Volcanic Formations

Ammavaru lava flows

Slide # 46: Volcanic Formations

lava flows and volcanism found across the planet

not found in specific lines or regions

Slide # 47: Volcanic Formations

pancakes (steep-sided domes)

Slide # 48: Volcanic Pancakes

formed by viscous lava flows

intermediate sized 20-100km diameter

Slide # 49: Atmospheric Changes

sulfur dioxide levels rise and fall irregularly

possible evidence of volcanic outgassing

radio energy seen around Aphrodite and Beta Regions

possibly similar to lightning seen near volcanos on Earth

Slide # 50: Surface Age of Venus

some large, old craters

about 1000 over the surface

thick atmosphere prevents small meteors from reaching surface

some lava flows free of craters

about 1/10 the cratering rate of the Moon

200 million to one billion year old surface

Slide # 51: Magnetic Fields

two conditions needed to form magnetic fields

liquid metal core

rapid rotation

weak magnetic field has been detect

Slide # 52: Venus

No detectable magnetic field

very slow rotation

Slide # 53: Overview of Geology

thin crust with active volcanos

no plate tectonics

lack of plates is not understood

mostly flat or rolling hills

two small uplift plateau