Lectures 7-12 Flashcards
(110 cards)
1
Q
What does the part of the Solary Sytem occupied by planets look like?
A
flattened, everything in almost the same plane
2
Q
What is the shape of orbits of dwarf planets?
A
very elliptical
3
Q
What is the shape of the orbit of the 8 major planets?
A
nearly circular, all orbit in same direction and nearly on the same plane
4
Q
Name the planets in order.
A
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune,
5
Q
Properties of the Sun
A
- over 99.9% of solar system’s mass
- mostly H and He gas (plasma)
6
Q
Properties of Mercury
A
- made of metal and rock
- large iron core
- desolate, cratered, cliffs
- very hot and very cold 425C day -170C night
7
Q
Properties of Venus
A
- almost the same size as Earth
- surface hidden by clouds
- extreme greenhouse effect
- even hotter than Mercury 470C day and night
8
Q
Properties of Mars
A
- looks like Earth
- polar caps, canyonns…
9
Q
Properties of Jupiter
A
- much farther from Sun than the inner planets
- mostly H/He
- no solid surface
- 300x the mass of Earth
- many moons, rings
- Galilean moons= Io,Europa,Ganymede,Calisto
10
Q
Properties of Saturn
A
- giant, gaseous like Jupiter
- rings= not solid made of small chunks of ice and rock each orbiting like a small moon
- many moons (incl. Titan)
11
Q
Properties of Uranus
A
- smaller than Jupiter and Saturn, still much larger than Earth
- H/He gas and hydrogen compounds (H2O,NH3,CH4)
- extreme axis tilt
- moons and rings
12
Q
Properties of Neptune
A
-similar to Uranus but not the axis tilt
13
Q
Properties of Pluto and other dwarf planets
A
- much smaller than major planets, icy-comet like composition
- pluto has a moon Charon= almost the same size as Pluto
14
Q
Properties of terrestrial planets
A
- smaller size and mass
- higher average density
- made mostly of rocks and metals
- solid surface
- few if any moons and no rings
- closer to the Sun and together with warmer surfaces
15
Q
Properties of jovian planets
A
- larger size and mass
- lower average density
- made mostly of H He and hydrogen compounds
- no solid surface
- rings and many moons
- farther from the Sun and from each other with cooler temperature cloud tops
16
Q
How do you measure the distance to Venus?
A
Measure apparent position of Venus on Sun from two locations on Earth.
- use trigonometry to determine Venus’ distance from the distance between the two locations on Earth
- that’s how we measured the AU
17
Q
What is a transit of a planet?
A
When planet passes between the Earth and the Sun and you can see it on the Sun.
18
Q
What is a flyby mission?
A
-fly by a planet just once, captured by gravity and sling shot further Voyager 1 (1977)125 AU away -at the edge of the solar system 19 billion km Voyager 2 (1977) 101 AU, 15 billion km away
19
Q
Describe the nebular theory
A
-Solar system formed from the gravitational collapse of a giant interstellar gas cloud
20
Q
What are the exceptions to the usual pattern in the Solar System?
A
- Uranus’ tilted axis
- Earth’s large moon
- Venus’ rotation
21
Q
What is meant by galactic recycling?
A
Elements that formed planets were made in stars and then recycled through interstellar space
22
Q
What caused the orderly patterns of motion in our solar system?
A
Conservation of angular momentum.-increasing speed of rotation with contraction
Flattening-collisions between particles in the cloud
23
Q
Why are there two major types of planets?
A
- as cloud contracting it heats up, inner part hotter than outer, rock can be solid at higher temp than ice
24
Q
What is the frost line?
A
A line inside which too hot for hydrogen compounds to form ices,
outside= cold enough to form ices
25
How did the terrestrial planets form?
- small particles of rock and metal inside the frost line
- planetesimals built up as the particles collided
- gravity eventually assembled these into terrestrial planets= accretion
26
Explain accretion of planetesimals.
Gravity draws them together, many small ones collected into bigger objects, eventually planets.
27
How did the jovian planets form?
- ice formed small particles outside the frost line
- larger planetesimals and planets able to form
- gravity of rock and ice in jovian planets draws in H and He gases, so that's why they're bigger-gas doesn't take as much gravity.
- each jovian planet is like a miniature solar system
28
What is the composition of the Solar system?
98% H and He gas don't condense in the nebula
1. 4% hydrogen compounds (H2O, methaneCH4,ammonia NH3) -condense at 150K
0. 4% rock-various mineral-condense at 500-1300K
0. 2% Metal-iron,nickel,aluminum condense at 1000-1600K
29
How come there isn't any H He gas floating around anymore?
Combination of photons and solar wind blew them away.
30
How did Sun's rotation change over time with regard to the nebular theory?
- the young Sun rotated much faster than now
| - friction between solar magnetic field and solar wind probably slowed it down.
31
What are asteroids and comets?
The leftover junk from the planetary accretion process.
32
Where are the rocky asteroids in the solar system?
Inside the frost line.
33
Where are the icy comets in the solar system?
Outside the frost line.
34
Why are many planets cratered?
Leftover planetesimals bombarded other objects in the late stages of solar formation.
35
Where does the water on Earth come from?
Probably came from icy planetesimals.
36
What is a possible explanation for some of the unusual moons in the Solar system?
They may be captured moons, unusual shape because not massive enough to be round.
37
How did we get our Moon?
- Mars sized planetesimal crashes into the Earth
- Hours later, Earth molten and rotating rapidly, lot of debris around, some goes on Earth surface and some will accrete to create the Moon
- 1000 yrs later accretion of the Moon done and little debris left
38
What explains the odd rotation of Uranus and Venus?
-giant impacts
39
How old is the Solar System? and how do we know?
- finding oldest rocks, radioactive dating is the most useful, oldest rocks in Greenland, WA , moon rocks and meteorites-
- about 4.54 billion years old rocks
- so planets probably formed at 4.5 billion yrs ago
40
Explain the basic idea of radioactive dating?
- all elements in a rock formed at the same time
- no new parent or daughter formed at later times
- the half life is known
- process: count the number of parent and daughter atoms
41
What is half-life?
Some isotopes decay into other nuclei, a half life is the time for half the nuclei in a substance to decay
42
What is the Earth's interior?
Core- highest density: nickel and iron
Mantel-moderate density: silicon, oxygen etc.
Crust- lowest density: granite, basalt etc.
43
How do terrestrial planets differentiate?
- Gravity pulls high-density material to the centre
- Lower density material rises to surface
- Material ends up separated by density
44
What is the litosphere?
- a planet's outer layer of cool,rigid rock
- it floats on the warmer, softer rock that lies beneath
- crust and part of mantle
45
What do P waves do?
P waves push matter back and forth
46
What do S waves do?
S waves shake matter side to side
47
How do we know what's inside the Earth?
-P waves go through the Earth's core but S waves don't so we Earth's core must have a liquid layer.
48
Why is the Earth's core hot?
- in the beginning: accretion and differentiation when planets were young
- today: radioactive decay is most important source today
49
How does a planet's interior cool?
- convection: transports heat as hot material rises and cool material falls
- conduction: transfers heat from hot material to cool material
- radiation:sends energy into space
50
Role of size in planet cooling?
Smaller worlds cool off faster and harden earlier
| -the Moon and Mercury are now geologically dead
51
Surface area to volume ratio and heat.
- heat content depends on volume
| - loss of heat through radiation depends on surface area
52
Why do some planets have magnetic fields?
- Magnetic fields are created by motions of charged particles
- A planet can have a magnetic fields if charged particles are moving inside it
53
Earth's magnetic field and requirements for its existence?
- molten electrically conducting interior
- convection
- moderately rapid rotation
54
Name the 4 main processes that shape terrestrial planets' surfaces.
- Impact cratering: asteroids and comets
- Volcanism: eruption of molten rock onto surface
- Tectonics: disruption of a planet's surface by internal stresses
- Erosion: surface changes made by wind, water or ice
55
Impact cratering-
most happened soon after the solar system formed
- craters ate about 10x wider than the objects that made them
- more small ones than big ones
56
Volcanism-
- volcanism happens when molten rock (magma) finds a path through litosphere to the surface
- molten rock is called lava after it reaches the surface
57
How does lava influence the surface? In terms of how thick it is.
- runny lava- makes flat lava plains
- slightly thicker lava males broad shield volcanoes
- thick lava makes steep stratovolcanoes
58
How does volcanism contribute to the atmosphere?
Outgassing, releases gases from Earth's interior to the atmosphere.
59
Explain tectonics?
- convection of the mantle creates stresses in the crust= tectonic forces
- compression of crust= mountain ranges
- valley forms where crust pulled apart
60
What drives erosion?
```
weather driven-
glaciers
rivers
wind
rain
```
61
How do craters reveal a surface's geological age?
Most cratering happened in the first billion years.
-more craters= older
younger regions= lava flooded
62
Why do larger planets (terrestrial) have more volcanism and tectonics?
They remain warmer inside for longer.
63
Why do larger planets have more erosion?
Because their gravity retains an atmosphere.
64
How does the distance from the Sun affect the terrestrial planets' climate and erosion?
- closer to the Sun too hot for rain, snow and ice= less erosion
- hot planets have more difficulty maintaining an atmosphere (kinetic energy)
- planets far from the Sun too cold for rain, limiting erosion
- planets with liquid water have the most erosion
65
Effect of planet rotation on weather, erosion and magnetic field?
- slower rotation= less weather, less erosion,weak magnetic field
- faster rotation= more weather, more erosion, stronger magnetic field
66
Why does Mercury have long steep cliffs?
It shrunk and some of the crust was forced to slide under others.
67
What is Olympus Mons?
volcano on Mars, the largest in the solar sytem
68
What is the origin of valleys on Mars?
Tectonics
69
Did water flow on Mars?
Likely. Erosion that looks to have been caused by water on the surface.
- there are rocks on Mars that seem to have formed in water
- there is still lot of hydrogen, normally it escapes fast so there must be source of it somewhere on Mars
70
How do you explain the difference in cratering densities on the Moon?
-younger regions flooded by lava- no craters= maria
71
Is there water on the Moon?
Most certainly.
72
What does the surface of Venus look like?
Must use radar due to clouds.
Impact craters but fewer than the Moon, Mercury and Mars
-shield volcanoes
-fractured and contorted surface= tectonic stress but not recently
73
Why do you not want to live in California?
The San Andreas Fault= earthquakes every 150 years, last one in 1857
74
How thick is the Earth's atmosphere?
10 km. (mostly N2 and 02)
75
What are the effects of an atmosphere on a planet?
- creates pressure determining if liquid water can be on the surface
- absorbs and scatters light
- creates wind, weather and climate
- interacts with the solar wind to create a magnetosphere
- can make surface warmer due to greenhouse effect
76
What is albedo?
Planet's reflectivity, the fraction of incoming sunlight it reflects.
low albedo=absorb more sunlight, leading to hotter temperatures
77
What is Greenhouse effect?
- visible light passes through the atmosphere and warms the surface
- the atmosphere absorbs infrared light from the surface, trapping heat
78
What would be the Earth's average temperature if there was no greenhouse effect?
- 16 now average 15
| - 31C difference
79
How much colder would Venus be without the Greenhouse effect?
510C colder
80
How is Earth heated?
from below the surface
- light of different energies from the Sun
- mostly visible light reaches the surface
81
What is ionisation in the atmosphere?
removal of an electron (UV, X-Ray)
82
What is dissociation in the atmosphere?
destruction of a molecule (UV, X-Ray)
83
What is scattering in the atmosphere?
change in photon's direction (optical)
84
What is meant by absorption in the atmosphere?
Photon's energy is being absorbed (IR).
85
What is the troposphere?
- closest to earth
| - lowest layer warmed by IR light from Earth's surface
86
What is the Stratosphere?
above troposphere, warmed by UV from the Sun
| -has ozone layer in it
87
What is the Thermosphere?
-above stratosphere, warmed by X-Ray and UV from Sun
88
What is Exosphere?
-above thermosphere, fades into space =100km =space
89
Describe how far does light of different energies get in the atmosphere?
Least- X ray, then UV and most visible
90
Why is the sky blue?
-Atmosphere scatters blue light from the Sun making it appear come from different directions.
Sunsets are red because red light scatters less.
91
Why is the magnetic field important for us on Earth?
It protects us from the charged particles streaming from the Sun (solar wind).
92
How is aurora generated?
Charged particles from solar wind energise the upper atmosphere near magnetic poles.
93
What is weather?
-the daily variations in wind, clouds, temperature, and pressure; local and hard to predict
94
What is the climate?
-the long-term average of weather; long-term stability of climate depends on global conditions and is more predictable
95
What produces circulation cells?
The hot/cold of the equator and the poles plus the Earth's rotation, if without rotation= just two cells, with= 6
96
What is solar brightening?
The Sun gradually grows brighter with time, increasing the amount of sunlight warming the planets.
97
How does the changing of axis tilt affect weather?
- seasons
- larger tilt= more extreme seasons
- smaller= keeps polar regions colder
98
Does the tilt of the Earth's axis change?
-yes
-small gravitational tugs from other bodies in solar system cause the tilt to vary from 22 to 25 degrees.
(normally 23.5)
99
How can Earth's climate change?
- sun brightening
- axis tilt
- change in reflectivity
- change in greenhouse gases
100
What are the 3 major ways in which a planet can obtain an atmosphere?
- Outgassing from volcanoes
- Evaporation of surface liquid; sublimation of ice
- impacts of particles and photons
101
Can atoms escape the gravity of a planet when obtained enough thermal energy?
Yes.
| -more thermal energy= more kinetic energy= achieve escape velocity
102
Do the Moon and Mercury have any atmosphere?
- extremely thin, gas comes from impacts that eject surface atoms
- functionally NO!
103
Are there seasons on Mars?
Yes, because of the ellipticity of Mars' orbit= more extreme in southern hemisphere.
104
Describe the polar caps on Mars.
- residual ice of the south polar cap remains during summer= primarily water ice.
- carbon dioxide ice of polar cap sublimates as summer approaches and condenses at the opposite pole
105
How has the climate on Mars changed in history?
- hasn't had surface water for 3 billion years
- Greenhouse effect probably kept surface warmer before
- somehow Mars lost its atmosphere
106
Describe the atmosphere on Venus.
- thick, CO2 atmosphere with surface pressure 90x that of Earth= strong greenhouse effect
- slow rotation produces very weak Coriolis effect and little weather
107
What is runaway greenhouse effect?
If Earth placed in Venus' place= more sunlight= more evaporation= more greenhouse gas= more heat etc. till we're like Venus.
108
Why is Earth's atmosphere so different to all the other terrestrial planets?
- it's in the habitable zone, can have liquid water
- life changed it, decrease in CO2, increase in O2
- O2 led to ozone layer (ozone O3) when oxygen smashed by UV)
- Moon= a stable orbit
109
Why does Earth's climate stay stable?
Earth's thermostat, cooling allows CO2 to build up in the atmosphere and heating causes rain to reduce CO2 in the atmosphere
110
How can long term climate change look like + causes.
- changes in axis tilt= ice age
- widespread ice= higher reflectivity= lower temperature
- CO2 from outgassing would built up if oceans frozen and eventually raise global temperatures again
