Lesson 8 Flashcards
What is planetary geology?
Geology of the celestial bodies such as planets and their moons, asteroids, comets, and meteorites
What are the differences in the planets’ surfaces due to?
They are due to the effects of time (i.e. bombardments of asteroids)
What are the hallmarks of the surfaces of Mercury and the Moon?
craters
What are the hallmarks of the surface of Venus?
Many volcanoes
What is the hallmark of the surface of Mars?
Dry riverbeds and the largest volcanoes in the solar system
What is the hallmark of the surface of Earth?
living organisms
What is one clue as to the internal structure of a terrestrial planet?
Seismic waves
What two ways does earth experience seismic waves?
- transverse pressure (parallel to the ground)
- causes P waves (primary waves) to occur - perpendicular pressure (pressure towards the ground)
- causes S waves (secondary waves) to occur
Why should we conclude that Earth’s core must have a liquid outer layer?
Because P waves can travel through almost any material, but S waves can only travel through solid material
What are seismic waves?
Vibrations that travel through Earth’s interior and surface
What are seismigraphs?
instruments used to measure seismic activity
What is special about all of the terrestrial planets?
They all have layered interiors
How can we categorize the layers of terrestrial planets?
we can categorize them into the core, mantle and crust
Describe the core of a terrestrial planet?
Where the heaviest materials, like iron, are
Describe the mantle of a terrestrial planet?
Rocky materials like silicon make up the mantle
Describe the crust of a terrestrial planet?
Made of granite and basalt
What is differentiation?
The fact that gravity pulls high density material to the centre and lower density material rises to the surface
What is the likely explanation for why the interior of terrestrial planets are layered?
Because of differentiation
Which of the terrestrial planets is the most geologically active?
Earth
What three sources of energy explain the internal heat of a terrestrial planet?
- heat of accretion (from the kinetic energy of planetesmals)
- heat from differentiation
- heat from radioactive decay
What is radioactive decay?
When the mass energy in nuclei is converted to thermal energy
What three processes cool a terrestrial planet’s interior?
- convection - transports heat as hot material rises and cool material falls
- conduction -transfers heat from hot material to cool material
- radiation - sends energy into space
What is the lethosphere?
The outer layer of cool, rigid rock (which floats on the warmer, softer rock beneath)
What is geological activity?
ongoing changes in a terrestrial planet’s surface
Why is size a good control of geological activity?
Because a larger planet can stay hot inside for longer than a small planet
Which two terrestrial planets/bodies are geologically dead?
The moon and mercury (there is little heat-driven geological activity)
How are magnetic fields created?
When charged particles move at a constant velocity
- heat can create a global magnetic field
What does earth’s magnetic core serve to do?
It protects earth’s atmosphere from being stripped away into space by the charged particles
What are the three requirements for a global magnetic field?
- a molten, electrically conducting interior
- convection
- moderately rapid rotation
Which of the terrestrial planets is the only one to meet the three criteria for a global magnetic field?
Earth
What is an atmosphere?
A layer of gas that surrounds a world
What does the term “airless” refer to?
That the planet has almost no atmosphere, wind or weather of any kind (i.e. Mercury and the Moon)
What is special about Venus’ atmosphere?
It is so thick, that it traps the heat from the sun (so hot that not even robots can survive)
What is special about Mars’ atmosphere?
It is so thin that we would die without a pressurized suit
What is a bar?
A unit of atmospheric pressure
What does 1 bar equal?
1 bar = earth’s atmospheric pressure at sea level (1.03 kg/cm^2 = 14.7 lbs/in^2)
How thick is Earth’s atmosphere?
10 km thick
What causes atmospheric pressure?
collisions of N2 and O2
Why do pressure and density decrease with altitude?
Because the weight of overlying layers is less
What is the greenhouse effect?
This only occurs when the atmosphere contains gasses that trap infrared light (ex. water vapour, carbon dioxide and methane)
What altitude is considered to be the “edge of space”?
100 km high and over
What are the key effects of Earth’s atmosphere?
- pressure: determines if there is liquid water on the surface
- light: atmosphere absorbs and scatters light
- weather: atmospheres create wind, weather and climate
- magnetosphere: atmospheres interact with solar wind to create a magnetosphere
- greenhouse effects: atmosphere causes earth’s temperature to be warm enough to allow for liquid water to flow
