Question 1

Phobos orbits Mars eastward with a shorter period than Mars takes to rotate on its axis (also eastward). As a consequence Phobos is:

Accepted Answer

A) ahead of the tidal bulge it raises on Mars, so that Phobos is slowly drifting away from Mars. 
B) ahead of the tidal bulge it raises on Mars, so that Phobos is slowly drifting toward Mars. 
C) behind the tidal bulge it raises on Mars, so that Phobos is slowly drifting away from Mars. 
D) behind the tidal bulge it raises on Mars, so that Phobos is slowly drifting toward Mars. 
A) ahead of the tidal bulge it raises on Mars, so that Phobos is slowly drifting away from Mars. 
B) ahead of the tidal bulge it raises on Mars, so that Phobos is slowly drifting toward Mars. 
C) behind the tidal bulge it raises on Mars, so that Phobos is slowly drifting away from Mars. 
D) behind the tidal bulge it raises on Mars, so that Phobos is slowly drifting toward Mars.

Question 2

In view of Mars's tilted angle of rotation at 25° to the ecliptic, its very similar rotation period to that of Earth (24 h, 37 min), and its orbital period of nearly 2 years, what will be the seasonal variations on Mars, compared to those upon Earth?

Accepted Answer

A) very similar seasonal variations, but each season lasting about half as long as those upon Earth because of the different orbital periods 
B) very similar seasonal variations, including seasons lasting about as long as those upon Earth because of the similar rotation rates of the two planets 
C) very similar seasonal variations, but with each season lasting twice as long as Earth's seasons 
D) much smaller seasonal variations than Earth's seasonal variations because of Mars's distance from the Sun, each season lasting about twice as long as those upon Earth 
A) very similar seasonal variations, but each season lasting about half as long as those upon Earth because of the different orbital periods 
B) very similar seasonal variations, including seasons lasting about as long as those upon Earth because of the similar rotation rates of the two planets 
C) very similar seasonal variations, but with each season lasting twice as long as Earth's seasons 
D) much smaller seasonal variations than Earth's seasonal variations because of Mars's distance from the Sun, each season lasting about twice as long as those upon Earth

Question 3

In 2012, Curiosity found strong evidence for an ancient streambed. This was:

Accepted Answer

A) dry gullies along crater walls. 
B) rounded pebbles. 
C) sedimentary rocks. 
D) dry flood channels from an impact crater. 
A) dry gullies along crater walls. 
B) rounded pebbles. 
C) sedimentary rocks. 
D) dry flood channels from an impact crater.

Question 4

At the present time, how many tectonic plates does Mars have?

Accepted Answer

A) zero 
B) one 
C) two 
D) five 
A) zero 
B) one 
C) two 
D) five

Question 5

On Mars, the air pressure varies much more from one season to another than it does on Earth. Why is this?

Accepted Answer

A) Seasonal dust storms on Mars blanket the entire planet, increasing the weight of the atmosphere. 
B) Because the atmosphere of Mars is so thin, water vapor condensing on the polar ice caps in winter removes a much larger fraction of the atmosphere than on Earth. 
C) Because of the low density of the atmosphere, solar heating has a much larger effect on Mars than on Earth. 
D) On Mars, much of the CO2, the major constituent of the atmosphere, condenses out to the surface as snow. This gas is only a minor constituent in Earth's atmosphere. 
A) Seasonal dust storms on Mars blanket the entire planet, increasing the weight of the atmosphere. 
B) Because the atmosphere of Mars is so thin, water vapor condensing on the polar ice caps in winter removes a much larger fraction of the atmosphere than on Earth. 
C) Because of the low density of the atmosphere, solar heating has a much larger effect on Mars than on Earth. 
D) On Mars, much of the CO2, the major constituent of the atmosphere, condenses out to the surface as snow. This gas is only a minor constituent in Earth's atmosphere.

Question 6

Observers in the nineteenth century reported seeing many straight-line features crisscrossing the surface of Mars, and these were interpreted as canals constructed by intelligent beings. What is the most likely present-day explanation for these observations?

Accepted Answer

A) stationary linear cloud formations (mountain lee wave clouds) and weather fronts, rotating with the planet 
B) optical illusions caused by vague shadings on the planet surface 
C) rifts at the boundaries of geological tectonic plates 
D) lines of volcanoes similar to those of the Hawaiian Islands on Earth 
A) stationary linear cloud formations (mountain lee wave clouds) and weather fronts, rotating with the planet 
B) optical illusions caused by vague shadings on the planet surface 
C) rifts at the boundaries of geological tectonic plates 
D) lines of volcanoes similar to those of the Hawaiian Islands on Earth

Question 7

The thickness of the crust of Mars has been measured to be different under two different hemispheres. How was this measurement made?

Accepted Answer

A) by radar measurements from an orbiting spacecraft, detecting radar waves reflecting back from the interface between crust and mantle on Mars 
B) by drilling from Mars lander spacecraft into the crust of the planet, down to the mantle 
C) by measuring the effect of slight differences in gravitational field upon the motion of a spacecraft orbiting Mars 
D) by a seismology from the Mars landers, detecting the waves generated by Martian "earthquakes" as they passed through Mars 
A) by radar measurements from an orbiting spacecraft, detecting radar waves reflecting back from the interface between crust and mantle on Mars 
B) by drilling from Mars lander spacecraft into the crust of the planet, down to the mantle 
C) by measuring the effect of slight differences in gravitational field upon the motion of a spacecraft orbiting Mars 
D) by a seismology from the Mars landers, detecting the waves generated by Martian "earthquakes" as they passed through Mars

Question 8

The Mars Exploration Rovers were both landed at locations that seemed promising for uncovering evidence of ancient water flow on Mars. What did they find?

Accepted Answer

A) As expected, both found sedimentary rocks, evaporites, and hematite, all signs of abundant water on the Martian surface in the past. 
B) Neither rover discovered any signs that water had ever existed on the surface of Mars. 
C) Spirit found abundant signs, including pools of liquid water, that water exists at present on the Martian surface, while Opportunity found none. 
D) Spirit found few signs of past water flow but Opportunity found sedimentary rocks, evaporites, and hematite, all signs of abundant water on the Martian surface in the past. 
A) As expected, both found sedimentary rocks, evaporites, and hematite, all signs of abundant water on the Martian surface in the past. 
B) Neither rover discovered any signs that water had ever existed on the surface of Mars. 
C) Spirit found abundant signs, including pools of liquid water, that water exists at present on the Martian surface, while Opportunity found none. 
D) Spirit found few signs of past water flow but Opportunity found sedimentary rocks, evaporites, and hematite, all signs of abundant water on the Martian surface in the past.

Question 9

When do scientists think the Caloris Basin was formed, and why do they think this?

Accepted Answer

A) It must have been formed early in Mercury's history, because it is overlapped by many other craters, some of them quite large. 
B) It must have been formed early in Mercury's history, because the shock wave that created the jumbled terrain on the opposite side of the planet could only pass through Mercury when it was in a semi-molten state. 
C) It must have been formed about the middle of the Heavy Bombardment period, because the crater density within the basin is only about half the average crater density for Mercury. 
D) It must have been formed at the end of the Heavy Bombardment period, because the crater density in the basin is very low compared to the average crater density for Mercury. 
A) It must have been formed early in Mercury's history, because it is overlapped by many other craters, some of them quite large. 
B) It must have been formed early in Mercury's history, because the shock wave that created the jumbled terrain on the opposite side of the planet could only pass through Mercury when it was in a semi-molten state. 
C) It must have been formed about the middle of the Heavy Bombardment period, because the crater density within the basin is only about half the average crater density for Mercury. 
D) It must have been formed at the end of the Heavy Bombardment period, because the crater density in the basin is very low compared to the average crater density for Mercury.

Question 10

The early Martian atmosphere probably contained as much nitrogen as Earth's atmosphere. But the present Martian atmosphere is less than 5% nitrogen gas. Where did the original nitrogen gas go?

Accepted Answer

A) It was locked up in the rocks and minerals of the Martian surface. 
B) At the elevated temperatures of the early Martian atmosphere, nitrogen's average velocity was high enough to cause it to escape. 
C) As UV-absorbing H2O and CO2 were depleted, UV radiation penetrated the Martian atmosphere. This was absorbed by N2, which received enough energy to escape. 
D) It is still present in nitric acid droplets and vapors in the Martian clouds. 
A) It was locked up in the rocks and minerals of the Martian surface. 
B) At the elevated temperatures of the early Martian atmosphere, nitrogen's average velocity was high enough to cause it to escape. 
C) As UV-absorbing H2O and CO2 were depleted, UV radiation penetrated the Martian atmosphere. This was absorbed by N2, which received enough energy to escape. 
D) It is still present in nitric acid droplets and vapors in the Martian clouds.

Question 11

All of the following are characteristics usually associated with a planet-wide magnetic field. Which one does Mars lack?

Accepted Answer

A) some liquid in the core 
B) some solid in the core 
C) some electrically conducting material in the core 
D) a relatively rapid rotation rate 
A) some liquid in the core 
B) some solid in the core 
C) some electrically conducting material in the core 
D) a relatively rapid rotation rate

Question 12

A friend who says that he is an astronomer claims that he was outside at midnight a few weeks ago looking at Mercury. What should be your response?

Accepted Answer

A) "Oh, you must have been in Australia or South America since Mercury can be seen at midnight only from the southern hemisphere." 
B) "You must be mistaken, because Mercury NEVER appears in our midnight sky." 
C) "Really! Have you just purchased a new telescope? Mercury can be seen at midnight only through a telescope." 
D) "Congratulations, you have been fortunate enough to see Mercury on a very rare occasion." 
A) "Oh, you must have been in Australia or South America since Mercury can be seen at midnight only from the southern hemisphere." 
B) "You must be mistaken, because Mercury NEVER appears in our midnight sky." 
C) "Really! Have you just purchased a new telescope? Mercury can be seen at midnight only through a telescope." 
D) "Congratulations, you have been fortunate enough to see Mercury on a very rare occasion."

Question 13

When Mercury is at its least value of greatest elongation it is seen 18° from the Earth-Sun line. How long before sunrise (or after sunset) will Mercury be visible at this time?

Accepted Answer

A) 18 minutes 
B) a little less than 1 hour 
C) 2 hours 
D) 4 hours 
A) 18 minutes 
B) a little less than 1 hour 
C) 2 hours 
D) 4 hours

Question 14

Mars is best viewed from Earth when it is at opposition, but some occasions are more favorable than others. Why is this?

Accepted Answer

A) Mars has an elliptical orbit, and favorable oppositions occur when Mars is near perihelion in its orbit, and hence closest to Earth. 
B) Mars has an elliptical orbit, and favorable oppositions occur when Mars is near aphelion in its orbit, and hence closest to Earth. 
C) Mars's orbit is inclined at a significant angle to the ecliptic, so favorable oppositions occur when it is crossing the ecliptic plane while near opposition. 
D) Even though Mars moves in a circular orbit, the orbit of Earth is elliptical, and so favorable oppositions occur when Earth is near perihelion. 
A) Mars has an elliptical orbit, and favorable oppositions occur when Mars is near perihelion in its orbit, and hence closest to Earth. 
B) Mars has an elliptical orbit, and favorable oppositions occur when Mars is near aphelion in its orbit, and hence closest to Earth. 
C) Mars's orbit is inclined at a significant angle to the ecliptic, so favorable oppositions occur when it is crossing the ecliptic plane while near opposition. 
D) Even though Mars moves in a circular orbit, the orbit of Earth is elliptical, and so favorable oppositions occur when Earth is near perihelion.

Question 15

Why are there are so few solar transits of Venus across the Sun's face as it revolves in its orbit and passes through inferior conjunction?

Accepted Answer

A) The orbital plane of Venus is inclined at 3.4° to the ecliptic plane. 
B) The synodic period of Venus is very long because of the relative orbits of Earth and Venus. 
C) Venus revolves around the Sun in a retrograde direction compared to the other terrestrial planets. 
D) Venus rotates on its axis in a retrograde direction compared to the other terrestrial planets. 
A) The orbital plane of Venus is inclined at 3.4° to the ecliptic plane. 
B) The synodic period of Venus is very long because of the relative orbits of Earth and Venus. 
C) Venus revolves around the Sun in a retrograde direction compared to the other terrestrial planets. 
D) Venus rotates on its axis in a retrograde direction compared to the other terrestrial planets.

Question 16

Why does Venus experience fewer transits of the Sun than does Mercury?

Accepted Answer

A) The orbit of Venus has a larger incline angle to the ecliptic than does the orbit of Mercury. 
B) Mercury is closer to the Sun and thus orbits more frequently. 
C) The retrograde rotation of Venus inhibits transits of the Sun. 
D) The large eccentricity of Venus's orbit results in fewer transits. 
A) The orbit of Venus has a larger incline angle to the ecliptic than does the orbit of Mercury. 
B) Mercury is closer to the Sun and thus orbits more frequently. 
C) The retrograde rotation of Venus inhibits transits of the Sun. 
D) The large eccentricity of Venus's orbit results in fewer transits.

Question 17

The inner Martian moon, Phobos, is 28 km in diameter and 6000 km above the Martian surface. Earth's Moon is about 3500 km in diameter and 400,000 km from Earth. How big in apparent diameter (angular size) would Phobos be in the Martian sky when seen directly overhead compared to our own Moon as seen from Earth?

Accepted Answer

A) less than 1/100 the size of our Moon 
B) almost twice the size of our Moon 
C) about 1/12 the size of our Moon 
D) about half the size of our Moon 
A) less than 1/100 the size of our Moon 
B) almost twice the size of our Moon 
C) about 1/12 the size of our Moon 
D) about half the size of our Moon

Question 18

To measure the surface temperature of Venus, Mariner 2 measured emissions with wavelengths of 1.35 cm and 1.9 cm. The temperature of Venus is 730 K. What is the peak wavelength in the emission spectrum of Venus?

Accepted Answer

A) 1.35 cm 
B) 1.9 cm 
C) 4 
? m 
D) 6 nm 
A) 1.35 cm 
B) 1.9 cm 
C) 4 
? m 
D) 6 nm

Question 19

The reason the temperature on the dark side of Mercury is warmer than originally expected is that:

Accepted Answer

A) Mercury's large iron core conducts heat through the planet. 
B) Mercury does not rotate synchronously with its orbital period. 
C) several very active volcanoes on Mercury, produced by tidal stresses from the Sun, produce excess heat. 
D) winds in Mercury's tenuous atmosphere carry heat from the daytime side to the night side. 
A) Mercury's large iron core conducts heat through the planet. 
B) Mercury does not rotate synchronously with its orbital period. 
C) several very active volcanoes on Mercury, produced by tidal stresses from the Sun, produce excess heat. 
D) winds in Mercury's tenuous atmosphere carry heat from the daytime side to the night side.

Exam 11: Mercury, Venus, and Mars: Terrestrial, yet Unique

Phobos orbits Mars eastward with a shorter period than Mars takes to rotate on its axis (also eastward). As a consequence Phobos is:

In view of Mars's tilted angle of rotation at 25° to the ecliptic, its very similar rotation period to that of Earth (24 h, 37 min), and its orbital period of nearly 2 years, what will be the seasonal variations on Mars, compared to those upon Earth?

In 2012, Curiosity found strong evidence for an ancient streambed. This was:

At the present time, how many tectonic plates does Mars have?

On Mars, the air pressure varies much more from one season to another than it does on Earth. Why is this?

Observers in the nineteenth century reported seeing many straight-line features crisscrossing the surface of Mars, and these were interpreted as canals constructed by intelligent beings. What is the most likely present-day explanation for these observations?

The thickness of the crust of Mars has been measured to be different under two different hemispheres. How was this measurement made?

The Mars Exploration Rovers were both landed at locations that seemed promising for uncovering evidence of ancient water flow on Mars. What did they find?

When do scientists think the Caloris Basin was formed, and why do they think this?

The early Martian atmosphere probably contained as much nitrogen as Earth's atmosphere. But the present Martian atmosphere is less than 5% nitrogen gas. Where did the original nitrogen gas go?

All of the following are characteristics usually associated with a planet-wide magnetic field. Which one does Mars lack?

A friend who says that he is an astronomer claims that he was outside at midnight a few weeks ago looking at Mercury. What should be your response?

When Mercury is at its least value of greatest elongation it is seen 18° from the Earth-Sun line. How long before sunrise (or after sunset) will Mercury be visible at this time?

Mars is best viewed from Earth when it is at opposition, but some occasions are more favorable than others. Why is this?

Why are there are so few solar transits of Venus across the Sun's face as it revolves in its orbit and passes through inferior conjunction?

Why does Venus experience fewer transits of the Sun than does Mercury?

To measure the surface temperature of Venus, Mariner 2 measured emissions with wavelengths of 1.35 cm and 1.9 cm. The temperature of Venus is 730 K. What is the peak wavelength in the emission spectrum of Venus?

The reason the temperature on the dark side of Mercury is warmer than originally expected is that:

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

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