Deck 10: The Nature and Evolution of Habitability

Question 1

Over time, as they age, the habitable zone of stars like our Sun

A) move inward
B) remain the same
C) suddenly disappear
D) move outward

Answer 1

move outward

Question 2

If Venus had the same atmosphere as the Earth, it would

A) only be slightly warmer
B) be at exactly the same temperature
C) be very much warmer
D) be slightly colder

Answer 2

only be slightly warmer

Question 3

Which of the following provides evidence for active volcanism on Venus today and in the past?

A) the direct observation of erupting volcanoes from orbit
B) the presence of sulfuric acid clouds in the atmosphere
C) the detection from orbit of elevated levels of infrared radiation from volcanic features on the surface
D) Both B and C

Answer 3

Both B and C

Question 4

Around 4 billion years ago Venus could have been more Earth-like with liquid water on its surface because

A) Venus has a protective magnetic field
B) its atmosphere was thinner
C) Venus was farther from the Sun
D) the Sun was dimmer so Venus would have received less radiation

Question 5

Evidence for the loss of water from the atmosphere of Venus via the action of ultraviolet light comes from the

A) observation of auroras high in the Venusian atmosphere caused by the action of ultraviolet light on water molecules
B) fact that today, water is found only in the upper atmosphere of Venus
C) observation of an ozone layer in the atmosphere which is formed from the breakup of water molecules by ultraviolet radiation
D) observation of an excess of heavy hydrogen (deuterium) atoms in the atmosphere which are less easily able to escape once the water is broken apart

Question 6

When Venus first formed it had large quantities of water vapor in its atmosphere while today only very low levels of water are present. Where did most of the water vapor go?

A) it was destroyed in the atmosphere by ultraviolet light from the Sun
B) it became chemically incorporated into rocks in the crust
C) it was blasted into space by impacts
D) it escaped into space

Question 7

Which of the following statements regarding the determination of surface habitability and subsurface habitability of a planet is correct?

A) both surface and subsurface habitability can be determined only from robotic space probes
B) surface habitability can be determined remotely by studying reflected starlight from a planet, while determining subsurface habitability would require a robotic space probe
C) both surface and subsurface habitability can be determined by analyzing reflected starlight
D) subsurface habitability can be determined remotely by studying reflected starlight from a planet, while determining surface habitability would require a robotic space probe

Question 8

The Moon is in the habitable zone of the Sun at the same distance as the Earth but is not habitable. How can this be?

A) the Moon did have water on its surface in the past, but it was destroyed by high-energy particles from the Sun
B) the Moon has never had water on its surface at any time
C) the Moon is too small to retain an atmosphere necessary for liquid water to be stable
D) the Moon did have water on its surface in the past, but it was blasted off the surface by impacts

Question 9

Venus is located

A) near the outer boundary of the Sun's habitable zone
B) in the middle of the Sun's habitable zone
C) near the inner boundary of the Sun's habitable zone
D) outside the Sun's habitable zone

Question 10

Based solely on its distance from the Sun, we would expect the surface of Venus to be

A) colder than the Earth such that water would freeze
B) warmer than the Earth, but not so warm that liquid water could not exist
C) roughly the same temperature as the Earth so that water would mostly be in liquid form
D) very much warmer than the Earth such that liquid water could not exist on the surface

Question 11

Theoretical calculations suggest that Earth-sized planets could be habitable on their surfaces outside of habitable zones if they

A) have thick, hydrogen atmospheres
B) have thick carbon dioxide atmospheres
C) are tidally heated by several large moons
D) have larger irons cores

Question 12

A habitable zone

A) exists around all stars
B) only exists around stars which are identical to the Sun
C) only exists around stars which are similar to our Sun
D) only exists around one star, the Sun

Question 13

What is the definition of a star's habitable zone?

A) the range of distances from the star where planets with life have been detected
B) the range of distances from the star where rocky planets can form
C) the range of distances from the star where organic molecules can be stable on the surface of a suitable planet
D) the range of distances from the star where liquid water can be stable on the surface of a suitable planet

Question 14

The inner boundary of the Sun's habitable zone currently lies

A) between the orbits of the Earth and Venus
B) between the orbits of Venus and Mercury
C) exactly at the distance of the Earth's orbit
D) exactly at the distance of Venus

Question 15

Most of the carbon dioxide on the Earth

A) is locked up in carbonate rocks in its crust or is dissolved in the oceans
B) is trapped beneath the surface of the planet in gaseous form
C) has escaped into space
D) is located in its atmosphere

Question 16

Europa is located outside the Sun's habitable zone and yet may be habitable. How can this be?

A) Europa's subsurface ocean contains lots of minerals that allow water to remain liquid at much lower temperatures
B) Europa is continually being hit by comets and asteroids which keeps water beneath its surface liquid
C) Europa is tidally heated, allowing liquid water to exist beneath its icy surface
D) Europa is large enough to have appreciable heat trapped inside it to keep water beneath the surface liquid

Question 17

Apart from its distance from its parent star, what is the next most important factor that determines a planet's habitability?

A) whether it has a large moon
B) the size of the planet
C) the chemical composition of its atmosphere
D) the chemical composition of its surface

Question 18

When the Earth first formed it had large quantities of water vapor in its atmosphere while today the levels of water vapor are much lower. Where did most of the water vapor go?

A) it condensed into the oceans
B) it escaped into space
C) it froze forming the polar
D) became chemically incorporated into rocks in the crust

Question 19

If the Earth were to be moved to where Venus is today,

A) the oceans would evaporate, blocking light from the Sun and causing global temperatures to fall
B) carbon dioxide would be released from the oceans leading to higher temperatures but liquid water could still exist on the surface
C) the oceans would evaporate slightly producing a slightly warmer, more humid planet
D) the oceans would evaporate and carbonate rocks would decompose producing a runaway greenhouse effect much more severe than the one that exists on Venus today

Question 20

Most of the carbon dioxide on Venus

A) is trapped beneath the surface of the planet in gaseous form
B) has escaped into space
C) is present in its atmosphere
D) is locked up in carbonate rocks in its crust

Question 21

If life is present on Venus today, it will most likely be

A) inside large rocks that are protected from the heat
B) found in the atmosphere where highly acidic droplets of water can be found
C) endoliths living beneath the crust where liquid water may still be present
D) hyperthermaphiles found on the surface

Question 22

The minimum size that makes it possible for a planetary surface to remain habitable over long time periods is a size that allows

A) plate tectonics to be present
B) a magnetic field to be present
C) an atmosphere to be present
D) hot spot volcanism to be present

Question 23

A star less luminous than our Sun will have a habitable zone that is

A) narrower and closer to the star than the habitable zone of the Sun
B) wider and closer to the star than the habitable zone of the Sun
C) narrower and farther from the star than the habitable zone of the Sun
D) wider and farther from the star than the habitable zone of the Sun

Question 24

Stars much less luminous than the Sun have

A) wider habitable zones, increasing the odds of finding habitable planets and much longer lifetimes allowing life to appear and evolve
B) wider habitable zones, increasing the odds of finding habitable planets but lifetimes too short for life to appear
C) narrower habitable zones, decreasing the odds of finding habitable planets and lifetimes too short for life to appear
D) narrower habitable zones, decreasing the odds of finding habitable planets but much longer lifetimes allowing life to appear and evolve

Question 25

What can contribute to a planet losing its atmosphere?

A) thermal escape
B) large impacts
C) solar wind stripping
D) all of these

Question 26

The case of Mars tells us that which of the following is a critical factor in determining surface habitability?

A) planetary size
B) levels of geological activity
C) distance from the Sun
D) the presence of a magnetic field

Question 27

What role does an atmosphere play in surface habitability?

A) it exerts a pressure which allows liquid water to be stable
B) it protects the surface against harmful solar radiation
C) it helps generate a protective magnetic field
D) Both A and B

Question 28

If distance from the Sun were the only factor affecting surface habitability, which of the following would be habitable?

A) the Moon
B) Venus
C) Mercury
D) all of these

Question 29

Mars currently lacks surface habitability mostly because of

A) the chemical composition of its atmosphere
B) its distance from the Sun
C) its small size
D) the chemical composition of its surface

Question 30

Which of the following is a crucial factor in enabling habitability on the surface of a rocky planet?

A) size
B) distance from parent star
C) presence of an atmosphere
D) all of these

Question 31

Although stars much more luminous than our Sun have wider habitable zones, planets around them are unlikely to have developed life because high luminosity stars

A) have extremely short lifetimes of the order of millions of years
B) are not expected to form rocky, terrestrial planets
C) emit very high levels of short wavelength radiation
D) are very unstable

Question 32

Which is not a critical factor that determines the habitability of a rocky planet?

A) size
B) distance from parent star
C) presence of a magnetic field
D) presence of an atmosphere

Question 33

What is a possible reason why Venus does not have plate tectonics?

A) it is too small
B) its crust is too dry and stiff to break into plates
C) it has no partially molten iron core
D) Both A and B

Question 34

Stars much more luminous than the Sun have

A) narrower habitable zones, decreasing the odds of finding habitable planets and lifetimes too short for life to appear
B) wider habitable zones, increasing the odds of finding habitable planets but lifetimes too short for life to appear
C) narrower habitable zones, decreasing the odds of finding habitable planets but much longer lifetimes allowing life to appear and evolve
D) wider habitable zones, increasing the odds of finding habitable planets and much longer lifetimes allowing life to appear and evolve

Question 35

The case of Venus tells us that which of the following is a critical factor in determining surface habitability?

A) planetary size
B) levels of geological activity
C) distance from the Sun
D) the presence of a magnetic field

Question 36

The moist greenhouse effect refers to

A) the warming process by which water vapor rises into the upper atmosphere above the ozone layer where it is then broken apart by ultraviolet radiation
B) the point at which water is evaporating from the surface at a faster rate than it is condensing
C) the natural greenhouse effect due to clouds of water vapor in the lower atmosphere
D) an enhanced greenhouse effect above tropical regions of the Earth's surface

Question 37

A star more luminous than our Sun will have a habitable zone that is

A) narrower and farther from the star than the habitable zone of the Sun
B) narrower and closer to the star than the habitable zone of the Sun
C) wider and farther from the star than the habitable zone of the Sun
D) wider and closer to the star than the habitable zone of the Sun

Question 38

Although low luminosity stars are very common, the probability of individual stars having planets within their habitable zones is low because low luminosity stars

A) are not expected to form rocky, terrestrial planets
B) have very narrow habitable zones
C) have no habitable zones at all
D) are very unstable

Question 39

If we allow for a simple runaway greenhouse effect, the inner boundary of the Sun's habitable zone would be

A) roughly halfway between the orbits of Venus and Mercury
B) just outside the orbit of the planet Mercury
C) roughly half way between the orbits of the Earth and Venus
D) just inside the orbit of the Earth

Question 40

If we allow for moisture loss due to a moist greenhouse effect, the inner boundary of the Sun's habitable zone would be

A) just inside the orbit of the Earth
B) roughly halfway between the orbits of Venus and Mercury
C) roughly halfway between the orbits of the Earth and Venus
D) just outside the orbit of the planet Mercury

Question 41

According to optimistic estimates, the end of habitability of Earth will come about

A) a few hundred thousand years from now
B) a billion years from now
C) 3 to 4 billion years from now
D) 100 million years from now

Question 42

Long-term data on global carbon dioxide levels can be obtained from analyzing air trapped in

A) rocks
B) ice cores drilled out of the Antarctic ice sheet
C) the upper atmosphere
D) deep ocean sediments

Question 43

As the average surface temperature of the Earth rises, the Northern hemisphere of the Earth is warming more rapidly than the Southern hemisphere because

A) the Northern hemisphere contains more landmass which more readily absorbs solar radiation
B) during summer in the Northern hemisphere, the Earth is closer to the Sun
C) there is less ice in Arctic regions compared to the Antarctic regions so less radiation is reflected out into space
D) there are more clouds in the Southern hemisphere to reflect solar radiation out into space

Question 44

Compared to today, in the future, the Sun's habitable zone will be

A) wider and closer to the Sun
B) narrower and closer to the Sun
C) narrower and farther from the Sun
D) wider and farther from the Sun

Question 45

The atmospheric carbon dioxide concentration

A) is higher than it has been at any time during the last 800,000 years
B) is higher than it has been at any time during the Earth's history
C) has remained roughly constant during the last 800,000 years
D) is lower than it has been at any time during the last 800,000 years

Question 46

The recent gradual rise in the Earth's average surface temperature is commonly referred to as

A) global warming
B) the greenhouse effect
C) ozone depletion
D) global heating

Question 47

Today, global average temperatures are estimated using

A) orbiting satellites
B) weather stations
C) water temperature measurements by ships
D) all of these

Question 48

Over the last century, global average temperatures have

A) risen by about 0.85°C (1.5°F)
B) stayed approximately constant
C) risen by about 2.0°C (3.6°F)
D) risen by about 3.0°C (5.4°F)

Question 49

Why does the Sun brighten with time?

A) as time progresses, helium starts to fuse in the core, in addition to hydrogen, leading to an increase in brightness
B) as hydrogen is converted into helium in the core, the number of hydrogen nuclei decreases, decreasing the fusion rate. To maintain the balance with gravity pressing inward, the core compensates by shrinking and heating up
C) as time progresses, more and more heat is trapped inside the core, leading to an increase in brightness
D) as hydrogen is converted into helium in the core, the number of hydrogen nuclei decreases, decreasing the fusion rate. To maintain the balance with gravity pressing inward, the core compensates by expanding and cooling

Question 50

When the Sun ejects its outer layer into space to become a planetary nebula, most likely the

A) Earth will be ejected from the solar system
B) Earth will be destroyed
C) Earth's oceans will freeze solid
D) Earth will experience a runaway greenhouse effect followed by the total loss of its atmosphere

Question 51

When the Sun becomes a red giant

A) some life on Earth may still be able to survive on the surface
B) life will probably not be able to survive even beneath the surface
C) life may still be able to survive in the atmosphere
D) the Earth will be destroyed

Question 52

According to conservative estimates, the end of habitability of Earth will come about

A) 3 to 4 billion years from now
B) a few hundred thousand years from now
C) 100 million years from now
D) a billion years from now

Question 53

While there is no doubt that global temperatures are increasing, it is

A) now becoming clear that human activity is indeed a major contributor to global warming
B) now becoming clear that this effect is due to the slow brightening of the Sun
C) now certain that human activity has no effect on the Earth's climate
D) still not clear whether human activity is affecting the climate at all

Question 54

Measurements of carbon dioxide concentrations in our atmosphere over the past 800,000 years show

A) an indirect correlation with global surface temperatures
B) a direct correlation with global surface temperatures, only over the past century
C) no correlation with global surface temperatures
D) a direct correlation with global surface temperatures

Question 55

Evidence that the recent rise in carbon dioxide concentration is due to human activity and not natural factors comes from

A) the amount of the rise in the atmospheric concentration tracks almost perfectly with the amount of carbon dioxide being released by industry
B) estimates of changes in the amount of carbon dioxide from natural sources such as volcanoes and the oceans can account for no more than about 1% of the rise in the atmospheric concentration
C) the ratio of carbon isotopes is consistent with the increase in carbon dioxide levels coming primarily from the burning of fossil fuels
D) all of these constitute evidence

Question 56

If Mars had a thicker atmosphere with a strong greenhouse effect, the outer boundary of the Sun's habitable zone would lie

A) roughly halfway between the orbit of the Earth and Mars
B) just within the orbit of Mars
C) roughly halfway between the orbit of Mars and Jupiter
D) just beyond the orbit of Mars

Question 57

When the Sun was younger, how did its habitable zone compare with its habitable zone today?

A) narrower and closer to the Sun
B) narrower and farther from the Sun
C) wider and closer to the Sun
D) wider and farther from the Sun

Question 58

When the Sun runs out of nuclear fuel and expands to become a red giant,

A) the Earth's oceans will freeze solid
B) the Earth will be ejected from the solar system
C) the Earth will be destroyed
D) the Earth will experience a runaway greenhouse effect followed by the total loss of its atmosphere

Question 59

Climate models which have been developed over many decades

A) completely fail to match real climate data
B) match real climate data quite well
C) match real climate data perfectly
D) match real climate data, but only poorly

Question 60

The range of distances that has remained habitable for the entire duration of the Sun's lifetime is referred to as the

A) continuously habitable zone
B) habitable zone of consistency
C) zone of water stability
D) permanently habitable zone

Question 61

As global warming progresses, the

A) landmasses will warm the most
B) equatorial regions will warm the most
C) polar regions will warm the most
D) oceans will warm the most

Question 62

As global warming raises the moisture content in our atmosphere, storms will

A) become less numerous and less severe
B) disappear all together
C) become less numerous but more severe
D) become more numerous and severe

Question 63

Climate models which ignore human activity

A) completely fail to match real climate data
B) match real climate data quite well
C) match real climate data perfectly
D) match real climate data, but only poorly

Question 64

Climate models predict that due to the melting of the polar ice caps, sea levels by the end of this century

A) will remain stable due to increased evaporation into the Earth's atmosphere
B) may rise by several tens of meters
C) will actually fall by several inches due to increased evaporation into the Earth's atmosphere
D) may rise by several meters

Question 65

As global warming continues, weather patterns will change causing

A) some parts of the Earth's landmass to become warmer while other parts will experience more extreme winters. The ocean temperatures will continue to rise
B) only the oceans to become warmer while the landmasses will become colder
C) only the landmasses to become warmer while the oceans will become colder
D) all parts of the Earth's surface will become warmer