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PHYS 183 > Lecture 8 - Planetary Atmospheres > Flashcards

Lecture 8 - Planetary Atmospheres Flashcards

1
Q

what is an atmosphere?

A

layer of gas surrounding a planet

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2
Q

is there a boundary to an atmosphere?

A

there is no clear upper boundary –> exponentially falls off

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3
Q

how thick is the atmosphere? what is it made of?

A

10km

mostly N2 and O2

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4
Q

what happens >100km? what about >300km

A

> 100km is considered space

> 300km still has some small amounts of gas

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5
Q

what creates atmospheric pressure?

A

collisions of individual atoms or molecules in the atmosphere

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6
Q

what happens to pressure and density as altitude increases? why?

A

pressure and density decrease as altitude increases bc there is less weight from overlaying layers

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7
Q

what is Earth’s pressure at sea level in kg/in^2, lb/in^2, 1 bar?

A

1.03 kg/in^2

14.7 lb/in^2

1 bar

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8
Q

describe pressure balanced with balloon elasticity

A

STAYS INFLATED when inside/outside pressures are balanced

adding air molecules will increase the inside pressure so the balloon expands until balance is restored

heating the balloon increases the speeds of air molecules inside to increase the inside pressure so the balloon expands until balance is restored

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9
Q

what are 5 effects of the atmosphere?

A
  1. creates pressure that determines whether a planet has liquid water
  2. absorb and scatter light
  3. create climate, weather, and wind
  4. interact with solar wind to create a magnetosphere
  5. making planetary surfaces warmer thru greenhouse effect
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10
Q

what happens when the atmosphere scatters light?

A

bright daytime skies

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11
Q

what happens when the atmosphere absorbs light?

A

prevents dangerous radiation from reaching the ground

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12
Q

what occurs during the greenhouse effect?

A

visible light (small wavelengths) passes thru atmosphere and warms the planet’s surface

then atmosphere absorbs infrared light (long wavelengths) from the surface, trapping heat

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13
Q

what are 4 factors that cause long-term climate change?

A
  1. solar brightening
  2. change in axis tilt
  3. change in reflectivity
  4. change in greenhouse gas abundance
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14
Q

how does solar brightening contribute to long-term climate change?

A

sun is changing the amount of thermal energy it releases and grows brighter

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15
Q

how does a change in axis tilt contribute to long-term climate change?

A

makes seasons more or less extreme –> warmer summers prevents ice buildup which reduces reflectivity to make the planet warmer

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16
Q

how does a change in reflectivity contribute to long-term climate change? what causes a change in reflectivity (3)?

A

increased planet reflectivity = less sunlight absorbed
(i.e. change in amount of light entering the atmosphere)

due to increased:
1. cloud cover
2. ice cover
3. particles released from volcanoes

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17
Q

how does a change in greenhouse gas abundance contribute to long-term climate change?

A

more greenhouse gases = warmer planet

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18
Q

in general, what determines surface temp of a planet?

A

balance btwn energy from sunlight it absorbs and outgoing thermal radiation

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19
Q

what determines the amount of incoming sunlight to a planet?

A

distance from the sun

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20
Q

what determines the temperature differences btwn day and night on a planet?

A

planet’s rotation rate

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21
Q

what is a planet’s reflectivity? what is another name for reflectivity?

A

reflectivity is the fraction of incoming sunlight it reflects

aka ALBEDO

22
Q

what happens if there is low albedo?

A

absorbs more sunlight –> hotter temp

23
Q

what is a “no greenhouse” temperature?

A

surface temp without any changes in atmosphere –> no greenhouse

24
Q

what planet has the greatest reflectivity? what does this indicate about its temperature?

A

venus

temp very high –> high greenhouse effect
- bc lots of sunlight absorbed and cannot escape

25
Q

how would the temperatures of venus and earth change if there was no greenhouse effect?

A

Venus would be 510deg C colder
Earth would be 31deg C colder

26
Q

what are the 4 layers of Earth’s atmosphere from low to high?

A
  1. troposphere
  2. stratosphere
  3. thermosphere
  4. exosphere
27
Q

TROPOSPHERE
- how does its temp change with altitude?
- what causes it to warm up?
- what is found here (2)?

A

temp drops with altitude

warmed by infrared light from surface and convection

airplanes, highest mountains

28
Q

STRATOSPHERE
- how does its temp change with altitude?
- what causes it to warm up?
- what planet is the only planet with a stratosphere? why?

A

temp rises with altitude in lower parts, then temp drops with altitude in upper parts

warmed from the top by absorption of UV sunlight

Earth is the only planet with a stratosphere bc of UV-absorbing O2 molecules which protect us from Sun’s UV light

29
Q

THERMOSPHERE
- at what altitude is it located at?
- how does its temp change with altitude?
- what 2 types of light is found here and what do they do?

A

located at 100km altitude

temp rises with altitude

X-rays and UV light from the sun heat and ionize gases

30
Q

EXOSPHERE
- what is it?
- how does temp change with altitude?
- what happens to atoms in exosphere?
- what 2 types of light play a role and what do they do?

A

highest layer in which atmosphere gradually fades into space

temp rises with altitude

atoms escape into space

warmed by X-rays and UV light

31
Q

why is the sky blue? why are sunsets red?

A

the atmosphere scatters blue light from the sun, making it appear to come from different directions

at sunset, there is more atmosphere to get through so blue does not cross. RED will cross but red gets scattered less

32
Q

what is the role of earth’s magnetic field?

A

acts as a protective bubble around the planet to deflect solar wind particles

33
Q

what happens to particles at the North and South poles?

A

some particles can accumulate in charged particle belts at either poles

34
Q

does the strength of magnetic fields stay the same or change over time?

A

strength of magnetic fields changes over time

35
Q

what causes an Aurora? when are they larger?

A

particles from solar wind energize the upper atmosphere near magnetic poles

larger when the sun is more active

36
Q

On mars, seasons vary btwn _______ and _______

A

On Mars, seasons vary btwn North and South

37
Q

how does the orbit of Mars affect its seasons?

A

orbit is elliptical so seasons are more extreme in the Southern hemisphere

spends more time away from the sun so winter is long and cold

38
Q

describe the evolution of the atmosphere on Mars

how has the core changed?

A

early atmosphere was preserved by magnetic fields from molten core that bent solar winds around it

then magnetic fields decreased due to interior cooling and the solar wind stripped the atmosphere

the core is now weaker

39
Q

describe surface water on Mars

A

no evidence of recent surface water, but there likely was water at some point

must have had greenhouse effect leaving long wavelength light in

40
Q

describe the south polar ice caps on Mars

A

Residual ice of the south polar cap remaining during the summer is mainly water ice

41
Q

describe the role of CO2 on Mars

A

CO2 makes up the ice of polar ice caps in winter

it sublimates in summer and condenses at the opposite pole

in ICE FORM, not in atmosphere so cannot warm the planet

42
Q

what is the evidence for water on Mars? where could liquid water be located?

A

radar imaging has found frozen waters in layers of dusty ice

liquid water may exist underground near sources of volcanic heat

43
Q

what is unique about the axis tilt of Mars? what does this lead to?

A

axis tilt changes –> ranges from 0-60

leads to climate changes and is evident in alternating layers of ice and dust

44
Q

describe the atmosphere and surface pressure of Venus

A

venus has a thick CO2 atmosphere with a surface pressure 90x that of Earth

45
Q

why does Earth have less of a greenhouse effect compared to Venus?

A

most of the carbon and water on Earth is in rocks and oceans

46
Q

is the rotation of Venus slow or fast? what 2 things does this lead to?

A

rotation of Venus is slow

produces:
1. weak Coriolis effect
2. little weather

47
Q

could Earth have had a larger greenhouse effect at one point? why?

A

yes, because of more carbon in atmosphere

48
Q

what is the runaway greenhouse effect?

A

as greenhouse effect gets stronger, there is feedback to make it MORE stronger

49
Q

why does the runaway greenhouse effect occur? (3)

A
  1. higher temp = more evaporation = more water vapour in atmosphere and it is a greenhouse gas which strengthens the greenhouse effect
  2. higher temp = oceans evapourate and release CO2 into atmosphere
  3. melting ice caps = less sunlight reproduction = more heat trapped and materials in permafrost could produce more heat as they melt
50
Q

how might runaway greenhouse effect affect Venus?

A

the runaway greenhouse effect could account for why Venus has so little water

PHYS 183 (20 decks)

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