Lecture 9

Question 1

Why can each Jovian planet been considered a miniature solar system?

Answer 1

Its formation resembles that of the Sun

Question 2

What are volatiles?

Answer 2

Chemicals that can be readily vaporised; these chemicals can be solid outside the frost line

Question 3

What happened to the remaining volatiles after planet formation ceased?

Answer 3

They were blown away by a combination of photons and the solar wind

Question 4

What does nebular theory say about the rotation of the sun?

Answer 4

It once rotated much faster than it does now

Question 5

What are some possible reasons for planet rotation to be slowing?

Answer 5

-Friction between the solar and magnetic field
-Solar wind

Question 6

Where are the short period comets located?

Answer 6

In the Kuiper belt (between Neptune and Pluto)

Question 7

Where are the long period comets located?

Answer 7

In the Oort cloud

Question 8

What special objects does the Oort cloud contain?

Answer 8

The Oort cloud contains primitive material that has not been touched by other objects in the solar system

Question 9

What is the heavy bombardment period and what is some evidence that supports it?

Answer 9

A period where leftover planetesimals bombarded other objects in the later stages of the solar system formation

Evidence for this period is found in the cratering of planets and moons

Question 10

What are some processes that cause planet resurfacing?

Answer 10

-Tectonics
-Magma
-Running water

Question 11

What are the theories for the origins of the Earth’s water?

Answer 11

-Water was brought as icy planetesimals from comets (only about 10% of the Earth’s water may have come this way)

-Water was present at the time of formation (evidence: significant amounts of water stored in the Earth’s crust and mantle and ratios of heavy H2 and H2O)

Question 12

What may some unusual moons be?

Answer 12

Captured planetesimals

Question 13

How was the Earth’s Moon formed?

Answer 13

-Mars size planetesimal crashes into the young Earth, shattering everything
-The Earth is molten and rotating very rapidly
-Debris that splashed out from the Earth’s outer layers now orbits the Earth and eventually accretes to become the Moon

Question 14

What strange planetary features can be explained by giant impacts?

Answer 14

-Axis tilt of Uranus
-Venus’ retrograde rotation

Question 15

What are some of the types of exoplanets?

Answer 15

-Gas giants
-Super-Earth
-Neptune-like
-Terrestrial

Question 16

What are two similar solar systems to ours?

Answer 16

-Kepler-90: contains 8 planets but with different compositions
-Trappist-1: similar sized planets to Earth with some having the potential for water

Question 17

What is alpha decay?

Answer 17

Radioactive decay that releases a helium nucleus

Question 18

What is beta decay?

Answer 18

Radioactive decay that releases an electron or positron

Question 19

What is the main principle of radioactive dating?

Answer 19

All elements in a rock were formed at the same time and no new parent or daughter substituents were formed out of the radioactive decay process

This means that known half-lives can be used to figure out the age of a rock

Question 20

What is an estimation for the age of the Earth?

Answer 20

4.54 +/- 0.05 billion years

Question 21

What is an estimation for the age of the Solar System?

Answer 21

4.56 billion years

Question 22

What does the Murchison meteorite show?

Answer 22

This 7 billion year old meteorite shows that some components of the solar system existed before becoming part of the solar nebula