ORIGINS: Creation and Composition of the Earth

Question 1

creation of the new solar system

Answer 1

• derived from the death of the previous one

- star becomes supernova, destroying itself, simultaneously creating new solar system (w elements)

Question 2

nebula to solar system

Answer 2

• gravitational energy is converted to heat (the cold cloud warms up)
• vapourizes all of the elements
• heat at the center lights up the sun
• gas/vapour blown away cools and recondenses as dust

Question 3

Condensation of planetesimals from dust and gas

Answer 3

• first by electrostatic forces, then by gravity

- elements interact, sharing and donating electrons

Question 4

rocky vs gas vs ice rich planets

Answer 4

• planets forming close to the sun are rocky
• planets condensing far from the sun are gas & ice rich
• the planets comprised of heavier elements (rocks) are (terrestrial planets) did not travel as far

Question 5

half-finished Earth (10-100MYA)

Answer 5

1. Earth bombarded by millions of smaller bodies (meteors and comets)
2. bombardment heated the Earth (collisions)
3. heating increased by gravitational contraction
4. melting of Earth creating magma ocean. Iron-rich fraction of this liquid was heavier and it settled to Earth’s centre
   * this melting drove off H, He- rich primordial atmosphere

Question 6

Earth 4.4 Ga (billion years)

Answer 6

• solid core (iron-rich)
• ‘outer core’ of liquid iron
• partly molten ‘mantle’
• thin skin of solid rock at its surface
• too hot for liquid water

Question 7

Jupiter and Saturn atmosphere

Answer 7

-close to the frost line

• gas giants as a result of no hot melting event
• retain a “primordial” atmosphere

Question 8

uranus and neptune

Answer 8

• light gases turned to ice
• made of mostly ice
• same composition as Jupiter and Saturn but at much lower temperature

Question 9

ontology of Earth’s Moon

Answer 9

• collision between large body and Earth
• moon grew from ejected material of this collision
• initially closer to the Earth

Question 10

on a moonless Earth:

Answer 10

• tides would be solar and less powerful
• days would be shorter
• faster winds

Question 11

Igneous Rocks

Answer 11

• “fire formed:” cooled from liquid
• the most accurate to date
• basalt, granite

Question 12

sedimentary rocks

Answer 12

• tell us about relative order in which events occurred

- formed from chemical precipitates or fragments of earlier formed rocks

Question 13

metamorphic rocks

Answer 13

-formed by application of heat and pressure to either igneous or sedimentary rocks

Question 14

radioactive decay

Answer 14

• useful until about 6 half lives

- measures proportions of parent and daughter isotopes of an element in SEVERAL samples

Question 15

age of the moon

Answer 15

• Earth’s major structures were established prior to the birth of the Moon
• BC an impact on Earth that did not have a separate Fe-rich core would have contributed more Fe to the moon
• by 4.4 Ga Earth and Moon were already a pair

Question 16

Bombardment of Earth and the Moon today

Answer 16

-prevented by LARGE Jupiter

Question 17

differences between the Earth and the Moon

Answer 17

• both heavily bombarded, yet the Moon has many more craters
• this is bc the moon is too small to hold a dense atmosphere
• also cooled much more rapidly, now has no volcanic activity and is lifeless

Question 18

Earth’s early atmosphere came from

Answer 18

• impact degassing (comets, bolides vapourizing)
• volcanic activity (gases released from magma)
• comets brought H2O, CO2, NH3 and many more building blocks of life, but could NOT bring O2 gas to the atmosphere