Astronomy Ch 9 - The Terrestrial Planets

Today we think that liquid water cannot exist on Mars due to the low atmospheric pressure. Select all the choices that are evidence that ice is present at or near the surface.

Ground-penetrating radar found the polar caps are mostly water ice. Landers have excavated ice.

The southern polar region of Mars is colder than the northern polar region. Why?

Higher altitudes at the southern pole lead to colder temperatures.

Select all the features that occur on Venus but are not found on Earth.

Grids of narrow cracks Pancake domes

The search for life on Mars is concentrated on finding ____.

liquid water microscopic life

Results of Venus's greenhouse effect include ____.

little change in temperature from day to night surface temperatures much hotter than can be explained by Venus's distance from the Sun

Venus, Earth, and Mars probably all started with similar atmospheres dominated by carbon dioxide. However, Mars lost most of its atmosphere because of its low ___ On Earth, most of the carbon dioxide is locked up in (carbonate) rocks, but some is also dissolved in the ___

mass water or ocean

Possible evidence for past life on Mars was found in a ___ on Earth.

meteorite

Mars's atmosphere has a percentage of carbon dioxide that is ____ Earth's and ____ Venus's.

much higher than; about the same as

Near its equator, the temperatures on Mercury ____.

peak at 710 K during the day and drop to 80 K at night

How are Mars's north and south polar caps similar?

Both caps shrink in summer. Both caps are mostly water ice.

Select all of the correct comparisons of Earth and Mars.

The length of a solar day is similar. Both planets have four seasons. Temperatures are sometimes above 0° C.

Select possible explanations for how Mars could have had a much thicker atmosphere and then lost it.

repeated impacts by asteroids blasted it away low gravity and a weak magnetic field allowed it to slowly escape to space

A ___ occurs when a periodically applied force causes a body's motion to grow larger.

resonance

The extremely hot and dense atmosphere of Venus is an example of ___ ___ effect.

runaway greenhouse

We can infer some of the history of Mercury's surface by looking at craters and lava flows. Place the following surface features in order of occurrence, from first at the top to last at the bottom..

1. Large impact crater 2. Lava flow 3. Small crater

Rank these planets by the ratio of craters to volcanoes, with the planet that has the most craters and fewest volcanoes at the top.

1. Mercury 2. Mars 3. Venus 4. Earth

Place the following in order of increasing size, with the largest at the bottom.

1. Moon 2. Mercury 3. Earth

Water is an effective medium for removing CO2 from a planet's atmosphere. Once rainclouds form, the process is underway. List the remaining steps in CO2 sequestration.

1. Rain droplets form and fall 2. CO2 dissolves in droplets 3. Droplets falls onto land or bodies of water 4. CO2 reacts chemically with rock or dissolved minerals forming carbonates

Model the process resulting in the Tharsis bulge by placing the following events in the correct order.

1. Rising material forces the surface upward 2. Hot material erupts through the crust 3. Volcanoes form from ejected material 4. Olympus Mons reaches its current height of 26 km

Comets may be the source of water ice deposits at Mercury's poles. Arrange the statements to describe the formation of polar ice deposits after a comet hits the surface.

1. The comet vaporizes on impact 2. Cometary material forms a wispy atmosphere 3. Some atmospheric particles drift toward the poles 4. Low temperatures freeze out cometary material, forming ices

Model the formation of the huge atmospheric vortices found at Venus's poles. Begin with the heating of the equatorial atmosphere.

1. The sun heats the atmosphere at the equator, causing it to expand 2. Low-density, warm gases rise to higher altitudes 3. Warm, upper-layer gases flow toward cooler polar regions 4. Cooling gases sink to lower altitudes and flow back to the equator

Rank the terrestrial planets by the mass of their atmospheres, putting the one with the most atmosphere at the top.

1. Venus 2. Earth 3. Mars 4. Mercury

Rank the objects according to how cold their interiors are, with the coldest at the bottom.

1. Venus 2. Mars 3. Mercury 4. Earth's moon

Put the missions to Mars in chronological order, from oldest to most recent.

1. Viking 1 & 2 2. Pathfinder 3. Spirit and Opportunity 4. Curiosity

Arrange the statements to model the loss of water on Venus.

1. Warm temperatures evaporate any surface water 2. Water vapor rises in the atmosphere 3. Sunlight breaks water molecules into H and O 4. Hydrogen escapes into space

Arrange the following regions of the Venusian atmosphere according to height. Put the ground at the bottom and move upward.

1. Wind speeds of 350 km/hr blowing toward the poles 2. Clouds of sulfuric acid droplets 3. Slow-moving winds 700 K temperatures, orange skies 4. The ground, with lava flows and possible volcanic vents

One (solar) day on Mercury is ____.

176 Earth days. an extremely long solar day

One year on Mercury is ____.

88 Earth days shorter than a solar day on Mercury

Mercury's orbit around the Sun is ____.

88 Earth days long elliptical in shape

Match the features to the names.

A - Craters B - Scarp C - Lava flood plains

Match the stages of evolution of a terrestrial object with the time order shown in the image.

A - Solid crust forms and is cratered by planetesimals. B - Lava floods fill large craters C - Volcanoes, uplifts, and plate motions can occur with molten mantle convection. D - Solidified mantle halts surface activity. matches E - Interior cools off and all tectonic activity stops. matches

Several properties of Earth are listed. Select the ones that are about the same for Venus.

A core made of iron-nickel and a mantle of rocky silicates Total mass of about 1 M⊕

Match each terrestrial planet with the atmosphere you might expect it to have.

A large planet with no liquid water - thick CO2 A small planet with no life - thin CO2 A large planet with liquid water and life - medium, N2 and O2

Terrestrial planets have many similarities. Select all the features that Earth and Mars have in common.

A wide variety of terrains Visible craters Polar ice caps High thin clouds

Your vehicle is stuck in a snowdrift, the tires caught in a U-shaped dip. Thinking back to Astronomy class, you recall that creating a resonance will help you get unstuck. When do you apply the gas to "rock" your vehicle out of the dip?

Apply as the car starts its forward motion.

Venus and Earth are similar in many ways. Identify all their properties that are very different.

Atmospheric composition Atmospheric density Surface temperature

Identify the layers of Mercury's interior.

C - Iron-Nickel core B - Silicate mantle A - Silicate crust

Of the following, select all the surface features that definitively suggest the Caloris Basin is the result of an impact.

Circular shape Ringed by mountains Chaotic terrain on opposite side of planet

Select all the accurate statements about Venus's rotation.

Combined with the orbital motion, it causes the solar day to be shorter than one rotation compared to the stars. It is retrograde compared to its orbit.

Select all the features we find on Venus's surface.

Continent-like masses Pancake domes Volcanic mountains

Which of the following is a consequence of Venus's crust being thicker than Earth's?

Convective motions in the interior are unable to break up the crust.

In this image of Mercury's surface, which formed first, the crater or the scarp running through it?

Crater

Match each planet with the description of its atmosphere.

Earth - Mostly nitrogen, some oxygen Venus - Very massive atmosphere, mostly CO2 Mars - Low-mass atmosphere, mostly CO2 Mercury - No atmosphere

Mars's interior is most similar to that of ____.

Earth and Venus

Of the following, select the features that Mercury and the Moon have in common.

Ejecta rays Lava flows Impact craters

What observations of the environment of Venus suggest that there are still active volcanoes on the planet?

Electrical discharges like lightning near volcanic peaks Brief increases in the sulfur content in the atmosphere Lava flows that appear fresh

True or false: Giovanni Schiaparelli observed canals on Mars.

False

True or false: Volcanoes on Venus such as Maat Mons (located to the right on the map) lie along plate boundaries, just as they do on Earth.

False - (Venus does not have plate tectonics; there are no plates)

Meteoric evidence for life on Mars includes both tiny, rodlike structures, and the presence of organic compounds, polycyclic aromatic hydrocarbons (PAHs). Which of the following are true of PAHs?

Form spontaneously given the proper mix of chemicals Substance produced when bacteria die

Some scientists believe these structures in a rock from Mars are ____.

Fossils of Martian bacteria. Results of chemical processes.

Why is the lack of large numbers of impact craters considered evidence that the volcanoes on Venus may still be active?

Frequent volcanic eruptions would cover over such craters on a ongoing basis.

Select all the features that are evidence of past geologic activity on Mars.

Giant volcanic mountains such as Olympus Mons Giant rifts such as the Valles Marineris

Select all the different types of observations that support the hypothesis that Mars once had large bodies of water on its surface.

Images show features that appear to be dried-up river channels or lakes. Compounds that form in water have been detected using spectra. Substantial ice is currently present in the polar caps and under the surface.

Select all the features that suggest that today, Mars has a cool, mostly inactive interior.

Lack of active volcanoes Lack of a magnetic field Lack of tectonic activity

Compared to rocks on Earth, Venusian rock has little water trapped in its structure. This results in ____

Less vigorous convection. Slowly flowing lava. A thick solid crust.

The body shown has a solid metallic core about half its total radius under a rocky mantle and a slightly lighter rocky crust. The body does not have a significant magnetic field. The object is most likely ____.

Mars

Mars's atmosphere is very thin relative to that of Venus and Earth. Why?

Mars cooled more quickly, reducing its internal activity.

Currently we do not detect liquid water on Mars's surface. Why?

Mars's atmospheric pressure is so low that liquid water evaporates immediately.

Select all that are sources for Mercury's tenuous atmosphere.

Material escaping from fractured rock Captured particles from the solar wind Gas seeping from the interior of Mercury

According to one hypothesis, the _____ spin of Venus is due to tidal braking caused by its ______ atmosphere.

slow and retrograde; massive and dense

Match the planet to the effect of sunlight on its atmosphere.

Mercury - 700 K temperature, no atmosphere Venus - Absence of water vapor due to evaporation, 700 K surface temperatures thanks to the greenhouse effect Earth - All phases of water stable on the surface Mars- Low surface temperature, liquid water freezes or evaporates quickly

Why is Mercury's daytime temperature so very high?

Mercury has little atmosphere. Mercury is close to the Sun. Mercury rotates slowly.

Why is Mercury's nighttime temperature so very low?

Mercury rotates slowly. Mercury has little atmosphere.

Mercury is a relatively flat place. Its differences in elevation are much less than those of the Moon and Earth. Why?

Mercury's interior is hotter and more molten. Mercury has stronger gravity than the Moon.

Why does Mercury have little atmosphere?

Mercury's temperature is very high. Any gases present have been stripped away by the Sun. Mercury's mass is very low.

Select all the accurate descriptions of Venus's atmosphere.

More than 90% CO2 Temperature hotter than Mercury's near the surface Clouds of sulfuric acid

Match the region of the Venusian atmosphere with its description.

Near the surface - Slow-moving winds, 700 K temperatures, orange skies Middle layers - Clouds of sulfuric acid droplets Upper atmosphere - Wind speeds of 350 km/hr blowing toward the poles

Match Mars's polar caps to their features. Use "Both" if the north and south pole have that feature in common.

North - ice strata indicating "ice ages" South - colder temperatures higher altitude Both - thin layer of CO2 ice, mostly water ice

Match the Martian surface feature with its description.

Olympus Mons - Largest mountain in the solar system Tharsis bulge - Huge uplands dotted with volcanoes Valles Marinaris - 4000-km long rift Northern polar cap - Persistent region of layered ices

Select all the statements that are true about Mars's moons.

Phobos is gradually spiraling inward and may crash into the surface in some millions of years. Mars moons have peculiar orbits.

Which feature from the surface of Mars is shown in the figure?

Polar cap

Which two of the following features seen in the images suggest substantial water flow once occurred on Mars?

River valleys Wakes behind craters

Select the surface features you might find on Mercury.

Scarps (Solidified) lava floods Craters Surface stretching and wrinkling

The idea of life on Mars is not a new one. Select all the early observations that stimulated interest in the idea.

Seasonal changes in surface features Apparent canali (channels) on Mars Early satellite photos depicting water-carved riverbeds

Which of the following is the best description of Mercury's interior?

Silicate skin on a large iron-nickel core

Mercury has smaller differences in elevation than does the Moon because it has ___ gravity and a ___ core.

Stronger Molten

Why is it cold enough for ice at Mercury's poles even though the planet is very close to the Sun?

Sunlight hits the polar regions at such a low angle that heating is very inefficient.

Select all the choices that are hypotheses of how Venus's internal heat affects its surface.

The crust is too thick to break into plates and move, but convection in the mantle causes bulges, volcanoes, and wrinkles in the crust. Heat builds in Venus's interior, melting the underside of the crust. Periodically, breaks occur and massive lava floods renew the surface. Rising plumes of melted rock stretch the surface and crack it. Domes, uplifted regions, and faults result.

Select all the statements that correctly describe this image.

The image shows evidence for past water on Mars. The little pebbles are called "blueberries.:

How does the existence of the chaotic terrain on the opposite side of Mercury from Caloris Basin support the idea that Caloris Basin formed as the result of an impact?

The impact created earthquake waves that traveled around the crust and converged on the opposite side of the planet.

Select the reasons why Mars's southern polar ice cap experiences larger changes than the northern ice cap.

The southern hemisphere has a higher average altitude than the northern hemisphere. Because of Mars's eccentric orbit, southern winters are colder than northern winters.

Venus has a rotational period of 243 days and an orbital period of 225 days. It spins backward (retrograde) compared to the orbital motion. Select all the consequences of these properties.

The stars that rise, rise in the west. The solar day is shorter than the rotation period. The Sun rises in the west.

Which of the following is true of Venus's atmosphere and weather?

The surface temperature is in excess of 700 K.

Why must water rise as a vapor to a high altitude in the atmosphere of Venus be be photodissociated?

The ultraviolet light that dissociates the water molecules cannot penetrate to the surface.

Select all that are true about the Martian moons.

They are only a few tens of kilometers across. They are named Phobos and Deimos. Their surfaces have craters and dust.

Mercury's orbital period is 88 Earth days. Its rotational period is 58.6 Earth days. From this and the figure, we can infer that ____.

Tidal interactions between the Sun and Mercury have been important The solar day (noon to noon) is 176 days Mercury spins three times for every two orbits

Mercury's solar day is twice as long as its year. True or false: As a result, sometimes the Sun travels backward across the sky during the day.

True - The Sun moves backward near perihelion, when the orbital motion changes the Sun's position faster than the rotation

How long does it take from sunrise to sunrise on Mercury?

Two orbital periods, a total of 176 Earth days

The composition of Mars's current atmosphere is most similar to that of which planet or moon?

Venus

The interiors of Venus and Earth are different in many ways. Match the characteristic to the planet.

Venus - slow convection, dry interior rock, thick solid crust Earth - runnier lava, plate tectonics

The reason for Venus's slow and retrograde spin is unknown. Identify hypotheses put forward by scientists to explain this behavior.

Venus was struck by a huge planetesimal, changing Venus's rotation. Tidal forces from the Sun and other bodies changed the tilt of the rotational axis.

Which statement best describes water on Venus?

Venus's water evaporated in the heat. Molecules drifted to the upper atmosphere and were split by ultraviolet light. The hydrogen escaped to space.

Identify reasons why we don't expect current missions to find liquid water surface of Mars.

Very low atmospheric pressure No rainfall Temperatures well below freezing point of water

What was the first mission to land on Mars with a goal of searching for evidence of life?

Viking

Match the missions to Mars to their descriptions.

Viking 1 & 2 - First successful landers; took pictures in 1976 Pathfinder - Launched the Sojourner rover to explore a dead flood plain Curiosity - Largest rover on Mars's surface, exploring geology and searching for ancient life Spirit & Opportunity - Rovers explored valleys, plains, and craters, analyzing rocks and soil

Why does the Tharsis bulge suggest that Mars' interior has been hot fairly recently?

Volcanoes in and around the bulge appear to be geologically young. The bulge is believed to have formed from material rising from the interior toward the surface.

How have we mapped the surface of Venus?

We have bounced radar off the surface from satellites and Earth.

Plants and animals changed Earth's early atmosphere from one like Venus's to our present one by ____.

absorbing CO2 into their structures, leaving behind N2 and O2

The temperatures at Mercury's poles ____.

are about 100 K all the time because they receive very little direct sunlight

Liquid water can alter a planet's surface and atmosphere by ____.

changing the chemical makeup of planetary rock causing erosion of surface rock absorbing atmospheric gases when it falls as rain

A likely weather report for summertime on Mars would be ______.

cool with gentle breezes, temperatures just above freezing. Good chance of dust storms

Estimates using ____ suggest the last time there was substantial liquid water on Mars was _________ years ago.

crater counts; 3 billion

Mercury's orbit is the most elliptical of any of the planets, with the distance from the Sun differing by almost a factor of two between closest approach (perihelion) and farthest (aphelion). Consequently, the intensity of sunlight at Mercury must vary by a factor of ____.

four, largest at perihelion

We expect surface tectonic activity only if a planet ____.

has a fluid interior with convection near the surface

Select each piece of evidence that supports the idea that Mars has water ice today.

ice revealed by digging up the Martian surface measurement of gamma rays coming from below the surface images showing a lake of ice inside a crater

Select all the methods astronomers have used to observe the surface of Venus.

images capture by robotic landers radar penetrating the thick clouds

On Earth, water vapor condenses in the troposphere, the lowest layer of the atmosphere, and travels no higher. If water vapor travels very high in a planet's atmosphere, ____.

it is dissociated by ultraviolet light, and the hydrogen is lost to space

The unusual circular features in this image of the surface of Venus are called ___ ___

lava domes

Olympus Mons (pictured) is the largest volcano in the Solar System, yet it exists on the modestly sized planet Mars, which has relatively few, but relatively large, volcanoes. This can be explained by the idea(s) that ____.

small planets cool quickly, and Mars developed a relatively thick crust with a small number of weak spots

Typical weather conditions on Mars are ____.

temperatures well below freezing gentle breezes, sometimes stronger wind high, thin clouds

In Earth's ozone layer, ultraviolet light breaks up O3 into O2 and free O atoms, which later recombine to form O3. In Venus's atmosphere, H2O rises to the top and is similarly broken up by ultraviolet light. The process is called photodissociation. On Venus, the atoms do not re-form into water because ____.

the freed hydrogen atoms are too light for Venus's gravity to hang on to, and many escape to space. The oxygen eventually combines with carbon

If there had been liquid water on Mars during the last 3 billion years, then ____.

the large number of craters would show evidence for erosion by water

Astronomers can tell a meteorite came from Mars when ____.

the mineralogy of the meteorite matches that of Mars gas trapped within the meteorite matches the Martian atmosphere

Evidence that Mercury has a molten core includes ____.

the presence of a magnetic field a slight wobble in Mercury's rotation

Mercury's orbit is the most elliptical of any of the planets, with the distance from the Sun differing by almost a factor of two between closest approach (perihelion) and farthest (aphelion). Consequently, the apparent diameter of the Sun as seen from Mercury must vary by a factor of ____.

two, largest at perihelion - (Angular size is inversely proportional to distance)

Over millions of years, life on Earth removed much carbon dioxide from Earth's original atmosphere and deposited oxygen in it by ____.

using CO2 dissolved in water to make shells plants absorbing CO2 to grow converting H2O into O2

The dominant source of a terrestrial planet's atmosphere is most likely ____.

volcanic eruptions

Because the crust of Mars does not shift like Earth's, ______.

volcanoes forming over hotspots never move away from the hotspots and thus grow very large

This image of the Martian surface shows evidence for ____.

water

The polar vortices in Venus' atmosphere behave most like ____.

water running down a drain

Mars's atmosphere is still steadily eroding due to ___ from the Sun. Mars doesn't have a strong enough ___ field to prevent this.

wind magnetic

Astronomers can tell that Mercury's core is molten because Mercury ___ as it spins on its axis and because it has a ___ field.

wobbles magnetic