What characteristic is used to differentiate gas planets from terrestrial planets?
Gas planets are differentiated from terrestrial planets by their density (their mass). The terrestrial planets, which are closer to the Sun, have much lower Earth masses than the gas planets.
What elements are common in the rocky planets?
silicon (Si), oxygen (O), aluminum (Al), magnesium (Mg), sulfur (S), and iron (Fe)
What is the most abundant rock type?
most abundant rock-type is common to all the rocky planets, and is called basalt, which is an igneous rock, the primary product of volcanic lava, fine grained, dark grey to black
Do planets close to the Sun experience more or fewer bombardments? Why?
The closer a planet is to the Sun - which has a massive gravitational attraction - the more often will it be bombarded by incoming asteroids and comets. Therefore, closer planets experience more bombardments
Learn the different models of the Moon’s origin and why one model is favoured
The Giant Impact Hypothesis is the preferred model. Here is what happened:
- collision(s) and melting of both bodies
- The glancing blow gave inc angular momentum to Earth (spin rate increased)
- The metal core of the impactor (the Mars-sized body) seperated and dropped into Earth, giving Earth its large metal core and remarkably high density
- To some degree, the molten mantle material of both bodies mixed, and formed debris in space just above Earth
- Over a relatively short period of time, some of the debris fell back to Earth, but most of it collected into a single mass to become the Moon
Fission Hypothesis – how did the Moon supposedly form? Why was this
hypothesis rejected?
- The earth was spinning very quickly and a chunk broke off that became the moon
- Rejected because it suggests the earth had to rotate once ever 2.5 hours which was difficult to reconcile with the current rotational rate
Condensation Hypothesis – how did the Moon supposedly form? What are the
two arguments against this hypothesis?
Both the earth and the moon formed from the same parental cloud of dust and gas
Rejected because 1) moon and earth would need to be the same composition which they don’t and 2) the moon would need to orbit earth exactly on an equatorial plane which it doesn’t
Capture hypothesis – how did the Moon supposedly form? Three reasons for
rejecting it?
The moon was captured by the earths gravitational force
Rejected because
1) the probability of an object the size of earth to fall into orbit about the earth is astronomically unlikely,
2) some chemicals (mostly oxygen isotopes) were so similar on the earth and moon that they must have some close ‘genetic’ relationship
3) every computer simulation of a capture failed miserably
Giant Impact hypothesis – what is it? (Why do we like this one?)
The Giant Impact hypothesis proposed that a planet somewhat smaller than Earth (hypothetical planet called Theia), in a progressively unstable orbit about the Sun, gave Earth a glancing blow sometime about 4.5 billion years ago
What is kinetic energy – how are energy and velocity related?
- Energy a body has by virtue of motion
- Kinetic energy increases exponentially with velocity
What is Theia?
- The hypothetical planet that was in a progressively unstable orbit about
the Sun
-Gave earth a glancing blow
How did the giant impact affect Earth’s structure?
- The energy of the impact(s) was enough to melt both planets
- Increased its spin rate
- The metal core of the impactor dropped into earth giving it its large metal
core and high density
What material makes up the Moon? Why is its composition similar to Earth?
The molten mantle of both bodies formed debris in space
What evidence is used to support that the Moon formed as a result of a large
impact?
- Tungsten isotopes that date more recently than the start of the solar system
- Oldest Moon rocks were formed when magma cooled so must have been
energy input enough to largely melt the moon - Oxygen isotopes almost same proportions as earth rocks
Was the impactor (Theia) large or small? Do we know?
It is not known for sure the size of Theia
Relate this hypothesis to the size of the Earth’s iron-rich core
The metal core of the impactor dropped into earth giving it its large metal
core and high density
EARTH..
be familiar with Size, density and internal zones
-Fifth largest planet
- Most dense at 5.5g/cm 3
- Zones: inner core, outer core, mantle, crust
EARTH..
Continental drift, plate tectonics, and magnetism
-Continents used to be a super continent called Pangea
- Then continents drifted apart
-Plate tectonics controls volcanism and earthquakes
-Strong magnetic field created by electric currents in iron-rich core
- Flow of liquid outer metal round solid inner metal core
EARTH..
Geological time and age dating
Two types of ways to date rocks:
- relative age dating (getting an age relative to rocks around it), or absolute dating (absolute years old).
EARTH..
Basic properties of the hydrosphere and atmosphere
- Atmosphere is 78% nitrogen, 21% oxygen and 1% traces of many other
elements
- Shelters earth from dangerous radiation
-Hydrosphere formed when water vapour in the atmosphere condensed and
it began to rain
-Hydrosphere is a closed system and earth has been recycling water for a
long time
What makes Earth unique among the terrestrial planets?
- Only planet in solar system that can currently support life
- Atmosphere is very unique to solar system
Explain the role of Accretion in the formation of the Earth
Accretion is growth by accumulation of smaller bodies, dust and gas. The first large object would have attracted others by simple gravity; and as the object grew larger, it attracted more and more material to it faster and faster
What is the iron catastrophe? How was the core formed? What are the layers of the core?
Hot liquid iron sunk deep to the core releasing energy that melted the whole
planet
What is the most common element in the Earth?
Iron making up around 30%
