AST101: Terrestrial Planets Pt.1

How do proto-planetary disks form?

The force of gravity pulls a molecular cloud (made of gas
and dust) together. As it collapses, it begins to spin faster (conservation of momentum). Collisions between particles flatten the orbit, forming a spinning disk of gas and dust

How does the frost line impact the formation of planets?

Terrestrial planets form within the frost line, only metal and rock (which make up terrestrial planets) can form into planets within the frost line as gas remains gaseous, outside the frost line, it is cold enough for gas to freeze into ice, which is used to form planets

What causes craters?

Craters are caused by the impact of planetesimals hitting the surface of planets

majority of craters were accumulated during the heavy bombardment, a period of time when planetesimals were repeatedly smashing into other objects

Mares are areas in which craters existed before hand, and were then filled in my volcanic activity

How are sound waves used to look under the surface of planets? Why is this necessary?

Machines called seismometers measure sound waves produced by earthquakes

Earthquakes produce vibrations in 2 forms - P waves (which are result of compressing and then stretching in the direction of travel), S waves (move up/down or side to side in the direction of travel)

What was discovered was that s wave paths can not travel through liquid - S wave paths also didn’t travel through the core of the earth, thus the core must be liquid

P waves did go through liquid, but bent and readjusted, which confirmed that there were other layers within the earth made of different material

What is differentiation?

The process in which the different materials in the earth separated and formed into different distinct layers (Core, mantle, crust, oceans)

Lighter materials (eg, lower density rock)
float to the surface, While heavier materials sink to the bottom (eg, Iron, nic)

Why are planets interiors hot?

How do planets interiors cool?

Convection - because hot rock weighs less, the hot rock will float to the surface of the earth while cooler rock sinks, and the cycle continues (The mantle is not rigid, and allows for this movement)

Conduction - heat from the rocks travels and escapes through the thin layer of the crust

Radiation - Infrared light (heat) carries energy (heat) away from the planet into space