ASTR178Other Worlds

A/Prof. Orsola De Marco9850 4241

orsola.demarco@mq.edu.au

Announcements• Website of the book. It contains many articles and links: http://bcs.whfreeman.com/universe9e/

Help questions (For this week)

• 1-28, page 232, 233.• Most of the questions in this chapter are relevantsince I covered this chapter pretty thoroughly.

The Moon Practical• All instructions have been posted on the website.• Download the instructions and the sky chart.• Go out at least 5 times between 14 August and 27 August ~8-9PM.• Plot the Moon position on the Sky Chart provided, includingthe Moon’s phase.• Always go out at the same time for instance sometime between 8 and 9 pm. IF YOU DO NOT THE EXPERIMENTWILL NOT WORK.• Answer the questions.• Return the work to the boxes by September 17.

How to use a Sky Chart

In last class• A quick wrap up of the magnetic fields in the Solar System.• Earth’s energy sources• The Greenhouse effect• Earth’s inner layers (we started it, we will finish in this class).

In this class• Earth’s inner layers• Plate tectonics• A few rock definitions• Earth’s early atmosphere and the rise of oxygen• Earth’s current atmosphere, temperature, pressure and circulation.• The Human effect on the atmosphere and climate.• We started talking about the moon, but this will be the subject of Week 4, Class 1.

Richard Dixon Oldham (Irish) 1858-1936Hypothesized the existence of a molten core.

Inge Lehmann (Danish)1888-1993Hypothesized the existence of the inner core

Plate tectonics

Alfred Wegener (German) 1880-1930

Arthur Holmes (British) 1890-1965

Roethosaurus – Early-mid JurassicFrom Queensland!

Tectonic activity is cyclic

• What we know of the tectonic movement (Pangaea to today) lasted ~200 million years.• Before then another cycle had taken place.The supercontinent before Pangaea was named Rodenia (1100-700 million years ago).• Tectonic activity has a ~500 million year “cycle”.

“Pangaea Ultima” a possible next supercontinenthttp://science.nasa.gov/science-news/science-at-nasa/2000/ast06oct_1/

Types of tectonic activity

• Converging – subduction zones (Chile coast)Himalayas

• Spreading – mid-Atlantic rift• Sliding – St. Andreas fault

Show Science Bulletins “Earthquakes today”: www.amnh.org/sciencebulletins/

All plate boundaries are sources of volcanism and earthquakes

Constructive and destructive plate boundaries

The St. Andreas Fault –a type of conservative plate boundary

A few “rock” terms

• Chemical elements make minerals (single atom or compounds)

• Single atom: diamond, gold nugget.• Compound: feldspar=K,Al,Si,O; quartz=Si,O)

• One or more minerals make rocks • Rock: granite = feldspar + quartz

Feldspar Quartz Granite

Plate tectonics and the variety of rocksAn example:

In the early Earth CO2 was outgassed from volcanos. As it dissolved in the oceans it formed carbonate minerals.One such mineral, calcite becamepart of sedimentary rocks such as limestone, which werelater subducted, mixed up resulting in,e.g., marble is a metamorphic rock.

Earth’s early atmosphere

• Early atmosphere: H, He, C, O, …. Same mix as the solar nebula• H, He easily escape, some H forms H2O which remains• Early atmosphere very dense and filled with water vapour• Earth cools, vapour becomes liquid, forms oceans• Earth would be very cold at this point, but CO2 outgassed from volcanoes is a green-house gas and keeps Earth warmer than itwould be otherwise.• CO2 is a green-house gas: in the atmosphere to keep the Earthwarm• Some CO2 dissolves in water and goes in the oceans where it is locked in rocks – some CO2 remains in the atmosphere• When we release too much CO2 in the atmosphere we increase the green-house effect and … the end of the story when we talk more about the roasting surface of Venus!

The rise of Oxygen and complex life

• Photosynthesis + Respiration: regulation of O2

•

Life on Earth

Protoplanetary disk(~4.5 Gyr ago)

First life (~3.8 Gyr ago)

Cambrian explosion (~500 Myr ago)

Humans (~100,000 yr ago)

The rise of oxygen

• Science Bulletin’s piecewww.amnh.org/sciencebulletins/

Comparing Earth’s, Venus’ and Mars’ atmospheres

50% of the atmosphere is in the troposphere.

Pressure decreases with altitude.Temperature is more complicated …

At hundreds of degrees, why isthe Shuttle notburning up?

The Earth biosphere

The Earth biosphere

• Climate can vary by natural causes (uneven Sun’s radiation, Earth’s axisprecession …).• CO2 levels can also vary naturally (intense periods of volcanic activity:extinction 250 million years ago driven by volcanoes in Siberia ….).• However, human influence ha been far above these natural chances (deforestation, destruction of the ozone layer, increase in CO2 emission).

90% of Ozone is between 40 and 60 km above ground.Ozone is O3. It is broken down by UV light so it absorbs UV light and protects us from it. It is then made by a reaction of O2 an O. It is alsodestroyed by reacting with O, a reaction that is catalysed by other chemicalssuch as CFCs

An Inconvenient Truth, by Al Gorehttp://video.google.com/videoplay?docid=2078944470709189270

Observations of the Moon• Aristotle thought that the lunar imperfections wereactually changes in density and the Moon was a perfect orb.• Plutarch (46-120 AD) suggested that it was due to canyons and valleys and might be inhabited.• It was Galileo that finally put the matter to rest using a telescope.

• Influence of the Moon on human life.

The MoonThe MoonThe MoonThe Moon

http://www.youtube.com/watch?v=RMINSD7MmT4

One small step for (a) man, one giant leap for mankind

Must watch the great Aussie movies “The Dish”.

Key Ideas

• The Earth’s Energy Sources: All activity in the Earth’s atmosphere, oceans, and surface is powered by three sources of energy.

• Solar energy is the energy source for the atmosphere. In the greenhouse effect, some of this energy is trapped by infrared absorbing gases in the atmosphere, raising the Earth’s surface temperature.

• Tidal forces from the Moon and Sun help to power the motion of the oceans.

• The internal heat of the Earth is the energy source for geologic activity.

Key Ideas• The Earth’s Interior: Studies of seismic waves (vibrations

produced by earthquakes) show that the Earth has a small, solid inner core surrounded by a liquid outer core. The outer core is surrounded by the dense mantle, which in turn is surrounded by the thin low-density crust.

• Seismologists deduce the Earth’s interior structure by studying how longitudinal P waves and transverse S waves travel through the Earth’s interior.

• The Earth’s inner and outer cores are composed of almost pure iron with some nickel mixed in. The mantle is composed of iron rich minerals.

• Both temperature and pressure steadily increase with depth inside the Earth.

Key Ideas

• Plate Tectonics: The Earth’s crust and a small part of its upper mantle form a rigid layer called the lithosphere. The lithosphere is divided into huge plates that move about over the plastic layer called the asthenosphere in the upper mantle.

• Plate tectonics, or movement of the plates, is driven by convection within the asthenosphere. Molten material wells up at oceanic rifts, producing seafloor spreading, and is returned to the asthenosphere in subduction zones. As one end of a plate is subducted back into the asthenosphere, it helps to pull the rest of the plate along.

Key Ideas

• Plate tectonics is responsible for most of the major features of the Earth’s surface, including mountain ranges, volcanoes, and the shapes of the continents and oceans.

• Plate tectonics is involved in the formation of the three major categories of rocks: igneous rocks (cooled from molten material), sedimentary rocks (formed by the action of wind, water, and ice), and metamorphic rocks (altered in the solid state by extreme heat and pressure).

Key Ideas• The Earth’s Magnetic Field and Magnetosphere: Electric currents in

the liquid outer core generate a magnetic field. This magnetic field produces a magnetosphere that surrounds the Earth and blocks the solar wind from hitting the atmosphere.

• A bow-shaped shock wave, where the supersonic solar wind is abruptly slowed to subsonic speeds, marks the outer boundary of the magnetosphere.

• Most of the particles of the solar wind are deflected around the Earth by the magnetosphere.

• Some charged particles from the solar wind are trapped in two huge, doughnut-shaped rings called the Van Allen belts. An excess of these particles can initiate an auroral display.

Key Ideas

• The Earth’s Atmosphere: The Earth’s atmosphere differs from those of the other terrestrial planets in its chemical composition, circulation pattern, and temperature profile.

• The Earth’s atmosphere evolved from being mostly water vapor to being rich in carbon dioxide. A strong greenhouse effect kept the Earth warm enough for water to remain liquid and to permit the evolution of life.

Key Ideas

• The appearance of photosynthetic living organisms led to our present atmospheric composition, about four-fifths nitrogen and one-fifth oxygen.

• The Earth’s atmosphere is divided into layers called the troposphere, stratosphere, mesosphere, and thermosphere. Ozone molecules in the stratosphere absorb ultraviolet light.

• Because of the Earth’s rapid rotation, the circulation in its atmosphere is complex, with three circulation cells in each hemisphere.

Key Ideas

• The Biosphere: Human activity is changing the Earth’s biosphere, on which all living organisms depend.

• Industrial chemicals released into the atmosphere have damaged the ozone layer in the stratosphere.

• Deforestation and the burning of fossil fuels are increasing the greenhouse effect in our atmosphere and warming the planet. This can lead to destructive changes in the climate.

Which of the following has the smallest effect on the motions of the Earth's atmosphere and oceans?

A. solar energy B. the Earth’s internal heat C. tidal forcesD. both B and CE. This is a misleading question. All of these have

comparably large effects on the atmosphere and oceans.

Q9.1

Which of the following has the smallest effect on the motions of the Earth's atmosphere and oceans?

A. solar energy B. the Earth’s internal heat C. tidal forcesD. both B and C.E. This is a misleading question. All of these have

comparably large effects on the atmosphere and oceans.

A9.1

What energy source creates clouds in our atmosphere?

A. The Sun B. Earth’s internal heat C. Tidal interactions with the MoonD. The solar windE. None of the above

Q9.2

What energy source creates clouds in our atmosphere?

A. The Sun B. Earth’s internal heat C. Tidal interactions with the MoonD. The solar windE. None of the above

A9.2

What energy source leads to mountain building on Earth?

A. The Sun B. Earth’s internal heat C. Tidal interactions with the MoonD. The solar windE. None of the above

Q9.3

What energy source leads to mountain building on Earth?

A. The Sun B. Earth’s internal heat C. Tidal interactions with the MoonD. The solar windE. None of the above

A9.3

In the greenhouse effect,

A. some infrared radiation emitted by the Earth’s surface is absorbed by the atmosphere.

B. some ultraviolet radiation emitted by the Earth’s surface is absorbed by the atmosphere.

C. vegetation traps thermal energy near the surface. D. infrared radiation from the Sun is captured as it

enters the Earth’s atmosphere. E. infrared radiation from the Sun is reflected by the

Earth’s atmosphere into space.

Q9.4

In the greenhouse effect,

A. some infrared radiation emitted by the Earth’s surface is absorbed by the atmosphere.

B. some ultraviolet radiation emitted by the Earth’s surface is absorbed by the atmosphere.

C. vegetation traps thermal energy near the surface. D. infrared radiation from the Sun is captured as it

enters the Earth’s atmosphere. E. infrared radiation from the Sun is reflected by the

Earth’s atmosphere into space.

A9.4

Which of the follow best describes the natural greenhouse effect (not including human influence) on Earth?A. There is no natural greenhouse effect. B. The natural greenhouse effect keeps Earth’s average

temperature relatively constant and above freezing. C. The natural greenhouse effect has continuously

increased the average temperature of the atmosphere and surface over the past 4.56 billion years.

D. The natural greenhouse effect has continuously decreased the average temperature of the atmosphere and surface over the past 4.56 billion years.

Q9.5

Which of the follow best describes the natural greenhouse effect (not including human influence) on Earth?A. There is no natural greenhouse effect. B. The natural greenhouse effect keeps Earth’s average

temperature relatively constant and above freezing. C. The natural greenhouse effect has continuously

increased the average temperature of the atmosphere and surface over the past 4.56 billion years.

D. The natural greenhouse effect has continuously decreased the average temperature of the atmosphere and surface over the past 4.56 billion years.

A9.5

Which of the following is not an important greenhouse gas?

A. Carbon dioxide B. Methane C. Water D. Ammonia E. All of these are important greenhouse gases.

Q9.6

Which of the following is not an important greenhouse gas?

A. Carbon dioxide B. Methane C. Water D. Ammonia E. All of these are important greenhouse gases.

A9.6

Which of the following is a correct statement about seismic waves used to map the Earth’s interior structure?

A. P waves are longitudinal and are able to travel through solids and liquids; S waves are transverse and can only travel through liquids.

B. P waves are transverse and are able to travel through solids and liquids; S waves are longitudinal and can only travel through liquids.

C. P waves are transverse and are able to travel through solids and liquids; S waves are longitudinal and can only travel through solids.

D. P waves are longitudinal and are able to travel through solids and liquids; S waves are transverse and can only travel through solids.

Q9.7

Which of the following is a correct statement about seismic waves used to map the Earth’s interior structure?

A. P waves are longitudinal and are able to travel through solids and liquids; S waves are transverse and can only travel through liquids.

B. P waves are transverse and are able to travel through solids and liquids; S waves are longitudinal and can only travel through liquids.

C. P waves are transverse and are able to travel through solids and liquids; S waves are longitudinal and can only travel through solids.

D. P waves are longitudinal and are able to travel through solids and liquids; S waves are transverse and can only travel through solids.

A9.7

The Earth’s magnetic field is generated by

A. electric currents in the liquid outer core; the field has never changed direction.

B. electric currents in the liquid inner core; the field has never changed direction.

C. electric currents in the liquid outer core; the field has reversed many times in the past.

D. electric currents in the liquid inner core; the field has reversed many times in the past.

E. electric currents caused by interactions with the solar wind.

Q9.8

The Earth’s magnetic field is generated by

A. electric currents in the liquid outer core; the field has never changed direction.

B. electric currents in the liquid inner core; the field has never changed direction.

C. electric currents in the liquid outer core; the field has reversed many times in the past.

D. electric currents in the liquid inner core; the field has reversed many times in the past.

E. electric currents caused by interactions with the solar wind.

A9.8

The Red Sea rift is

A. formed by two tectonic plates moving apart. B. a subduction zone, where one plate is pushed under

the other. C. a fold in the middle of a plate caused by compressing

forces on both sides of the plate. D. a hot spot in Earth’s mantle, which is spreading two

plates apart. E. the result of a earthquake that occurred thousands

of years ago.

Q9.9

The Red Sea rift is

A. formed by two tectonic plates moving apart. B. a subduction zone, where one plate is pushed under

the other. C. a fold in the middle of a plate caused by compressing

forces on both sides of the plate. D. a hot spot in Earth’s mantle, which is spreading two

plates apart. E. the result of a earthquake that occurred thousands

of years ago.

A9.9

The Mid-Atlantic Ridge is best described as

A. a line of undersea mountains caused by two plates colliding and pushing each other upward.

B. a fold in the middle of a plate caused by compressing forces on both sides of the plate.

C. a region where one plate is being subducted beneath another.

D. a site where two plates are moving apart, allowing molten subsurface rock to rise upward.

E. a region in the middle of a plate that happens to lie over a hot spot in the mantle.

Q9.10

The Mid-Atlantic Ridge is best described as

A. a line of undersea mountains caused by two plates colliding and pushing each other upward.

B. a fold in the middle of a plate caused by compressing forces on both sides of the plate.

C. a region where one plate is being subducted beneath another.

D. a site where two plates are moving apart, allowing molten subsurface rock to rise upward.

E. a region in the middle of a plate that happens to lie over a hot spot in the mantle.

A9.10

The Earth shows very little evidence of meteor impacts because

A. plate tectonics is continuously recycling the Earth’s crust.

B. wind and rain have continually eroded the Earth’s surface.

C. very few meteors struck the Earth in the past. D. vegetation has covered the craters.E. Both A and B are correct.

Q9.11

The Earth shows very little evidence of meteor impacts because

A. plate tectonics is continuously recycling the Earth’s crust.

B. wind and rain have continually eroded the Earth’s surface.

C. very few meteors struck the Earth in the past. D. vegetation has covered the craters.E. Both A and B are correct.

A9.11

If the early atmosphere of the Earth was composed of carbon dioxide, why does the present atmosphere contain oxygen molecules?

A. Volcanoes slowly enriched the Earth’s atmosphere with oxygen.

B. When life first developed on the Earth, this life produced oxygen from carbon dioxide by photosynthesis.

C. Rainwater slowly broke down carbon dioxide into its components.

D. Oxygen was captured from space over many millions of years.

E. Solar radiation breaks down CO2.

Q9.12

If the early atmosphere of the Earth was composed of carbon dioxide, why does the present atmosphere contain oxygen molecules?

A. Volcanoes slowly enriched the Earth’s atmosphere with oxygen.

B. When life first developed on the Earth, this life produced oxygen from carbon dioxide by photosynthesis.

C. Rainwater slowly broke down carbon dioxide into its components.

D. Oxygen was captured from space over many millions of years.

E. Solar radiation breaks down CO2.

A9.12

Ozone is a molecule made up of three oxygen atoms. The ozone layer that protects the Earth’s surface from ultraviolet light

A. has been present and stable for as long as we have been measuring it.

B. has shown gradual changes over the last 20 years with a hole appearing over Antarctica.

C. shows no holes yet but appears to be getting thinner. D. shows rather large seasonal changes with large holes

appearing over the North and South Poles during their respective winters.

E. is no longer present.

Q9.13

Ozone is a molecule made up of three oxygen atoms. The ozone layer that protects the Earth’s surface from ultraviolet light

A. has been present and stable for as long as we have been measuring it.

B. has shown gradual changes over the last 20 years with a hole appearing over Antarctica.

C. shows no holes yet but appears to be getting thinner. D. shows rather large seasonal changes with large holes

appearing over the North and South Poles during their respective winters.

E. is no longer present.

A9.13

The oxygen in our atmosphere is chemically reactive, combining with other elements to form compounds, and is also being used by respiratory life. Despite this, the amount of oxygen in our atmosphere is not decreasing because it is being replenished by

A. outgassing from seawater. B. volcanic eruptions. C. biological activity, such as photosynthesis. D. meteors and comets, which bring oxygen to the

Earth. E. solar radiation breaking down CO2.

Q9.14

The oxygen in our atmosphere is chemically reactive, combining with other elements to form compounds, and is also being used by respiratory life. Despite this, the amount of oxygen in our atmosphere is not decreasing because it is being replenished by

A. outgassing from seawater. B. volcanic eruptions. C. biological activity, such as photosynthesis. D. meteors and comets, which bring oxygen to the

Earth. E. solar radiation breaking down CO2.

A9.14