Chapter 9 Flashcards
What properties affect a planet’s outcome?
- Size
- Irradiation (distance from sun)
- rotation
- and other properties to a lesser extent
What does the interior look like for terrestrial planets?
Earth and venus are roughly the same in terms of interiors Mars and Mercury are vastly different mars has a large lithosphere whilst mercury has a large core.
What makes up the interior of a planet? from least dense to most dense
- Rocky crust (lower density)
- Litosphere (part of crust and mantle)
- Mantle (medium density)
- Metal core (high density)
Why are planets spherical?
After a certain size, the force of gravity on a planet is greater than the tensile forces within the rock. this deforms the shape into a sphere.
What were the dominant sources of heat in Earth’s early history?
Conversion from GPE to heat was main this was done through the accretion of planetesimals and differentiation converts PE to heat. Currently, radioactive decay produces the most heat
What three ways are heat transmitted or loss
- Convection
- Conduction
- Radiation
What does heat lead to?
heat drives geologic activity. This is because heat leads to convection which means that hot rocks rise and cool rocks fall.
What is the difference between smaller planets and larger planets, in terms of heat?
- Smaller planets cool faster so tectonic and volcanic activity ceases. The lack of volcanism means little outgassing and low gravity allows gas to escape more easily. No atmosphere means no erosion.
- Warmer interiors mean that tectonic and volcanic activity continues. Due to volcanism, outgassing produces a strong atmosphere and strong gravity holds it so that erosion is possible. The core may be molten which also creates a magnetic field if rotating fast enough.
What are the three requirements for a magnetic field
- Electrically conducting field
- Convection in fluid layer
- moderately rapid rotation
What are the four main geological processes?
- impact cratering - impacts by asteroids or comets
- volcanism - eruption of molten rock onto surface
- tectonics - disruption of a planet’s surface by internal stress
- erosion - surface changes made by wind, water, or ice
What is the main source of atmosphere on terrestrial planets?
outgassing is teh most importnat. There is also evaporation of surface liquids and ice and impacts of particles and photons on worlds without significant atmospheres can also release gasses from surface
What are tectonics and how do they work?
Convection in the mantle causes stress in the crust, pushing and pulling the crust together or pulling it apart and creating mountains or valleys.
How does erosion work?
erosion sculpts rocks, forming valleys, dunes, etc. this however requires an atmosphere (wind) and presence of water (liquid water and glaciers)
What causes erosion
- size the bigger the more outgassing the more erosion
- distance from the sun if too close then too hot for erosion if too far then too cold for erosion
- rotation the faster planet rotates the more wind it has.
Why are parts of the moon so smooth
- initially cratered surface
- large impacts damaged the lithosphere
- Molten rock leaks up and floods the large crater
- rock solidifies leaving a smooth surface.
How do craters help us determine age?
more craters = more age
Facts about Mercury and the Moons geology
The moon and mercury are now geologically dead. Mercury once had active volcanism and tectonics but Mercury contracted as it cooled. Forcing its crust to buckle
Mars geology?
Mars has had evidence of volcanism with huge mountains. it also has evidence of erosion and tectonics with certain places on mars looking like plates converged and erosion is evident with the river beds
Venus geology?
Venus has evidence of ongoing geological activity. There is evidence of impact cratering, volcanism and some signs of tectonics. That said there isn’t a lot of evidence of erosion this could be because of three main reasons: thick atmosphere, very minimal tilt and it may be too hot.
Earth’s geology?
Earth’s geology is driven by tectonic plates. In specific convergent plates and divergent plates.
What are convergent plates
convergent plates lead to huge mountain ranges. there are two main types of subduction which occur between land and sea and continental which occurs between land and land.
Olympus Mons creation on land near Hawaii
based on tectonic motions
What is an atmosphere
an atmosphere is a layer of gas surrounding a planet
Facts about pressure and density of the atmosphere
Higher density and higher temperatures cause higher pressure.
higher density = more particles to collide with each other.
Higher temperature = particles move faster
pressure and density of the air decline with height above sea level.
How much energy do we receive from the sun?
We can look at the Flux received. The further you go from the Sun, the more its light is spread out.
Flux received = L / 4 (pi) d^2
what two things would the temperature of a planet depend on without an atmosphere?
- How far it is from the sun (Flux)
- How reflective the surface is.
what are Greenhouse gasses?
Greenhouse gases are when visible light passes through the atmosphere and heat up the surface. the surface then emits radiation, primarily infrared. greenhouse gases in the atmosphere absorb infrared light trapping heat near the surface.
(CO2, H20, methane)
temperature with altitude?
forms an s line almost
What is thermal escape and when does it happen faster
thermal escape is a way that planets lose their atmosphere. This tends to happen faster for planets with low masses and strong irradiation
What are two ways a planet can lose its atmosphere?
- thermal escape
- solar winds - charged particles
What effect would greenhouse gases have on Mars?
All of mars water is frozen in its ice caps and is underground. greenhouse gasses could allow for higher surface temp resulting in the possibility of oceans
How did Mars lose its atmosphere?
With Mars as it cooled down, convection stopped it lost its magnetic field and therefore its protection from solar winds
What is the Carbon cycle
- atmospheric CO2 dissolves with rainwater
- rain erodes materials that flow into the oceans
- minerals combine with carbon to make rocks on the ocean floor
- continental drift carries carbon-rich rock down into the earth’s mantle
- Rock melts in the mantle and Co2 is outgassed back into the atmosphere through volcanoes.
what is the photodissociation of water?
outgassed water remained as vapour in the atmosphere leading to water losing its hydrogen atoms.
factors affecting climate change?
- changes in solar brightness
- changes in axis tilt
- changes in reflectivity
- an abundance of greenhouse gasses
