AST101 CH 9

Why does Mercury have little atmosphere?

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

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

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

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

Why is Mercury's daytime temperature so very high? (Select all that apply.)

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

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

Mercury rotates slowly. Mercury has little atmosphere.

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. Instructions

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

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

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

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

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

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

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

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

Results of Venus's greenhouse effect include ____.

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

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

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

The surface temperature is in excess of 700 K.

Mercury's orbit around the Sun is ____.

-88 Earth days long -elliptical in shape

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

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

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

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

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

One year on Mercury is ____. (Select all that apply.)

-shorter than a solar day on -88 Earth days

Evidence that Mercury has a molten core includes ____. (Select all that apply.)

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

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

1- moon 2- mercury 3- earth

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

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

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. Instructions

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. Instructions

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

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

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

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

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 Which of the following is true

One (solar) day on Mercury is ____. (Select all that apply.)

176 Earth days. an extremely long solar day

Compared to rocks on Earth, Venusian rock has little water trapped in its structure. This results in ____. (Select all that apply)

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

Match the features to the names. Instructions

A- Craters B- Scarp C- Lava Flood Planes

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 density Surface temperature Atmospheric composition

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

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

How are Mars's north and south polar caps similar? (Select all correct answers.)

Both caps are mostly water ice. Both caps shrink during the Martian spring and summer.

Identify the layers of Mercury's interior.

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

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.

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

Earth and Venus

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.

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

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

Ejecta rays Impact craters Lava flows

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 Reason: Correct. Venus does not have plate tectonics; there are no plates.

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 features that occur on Venus but are not found on Earth.

Grids of narrow cracks Pancake domes

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 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. Substantial ice is currently present in the polar caps and under the surface. Compounds that form in water have been detected using spectra.

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

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

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 the surface features you might find on Mercury.

Surface stretching and wrinkling Craters (Solidified) lava floods Scarps

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

Tharsis bulge

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

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

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

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 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.

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

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

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 ____. (Select all that apply.)

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

True or false: Mercury's odd rotation gives it an extremely long solar day. During that time, the Sun's motion across the sky appears to nearly stop then reverse direction slightly when Mercury is near perihelion.

True

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

Two orbital periods, a total of 176 Earth days Reason: The combination of Mercury's 58.7 Earth day rotation period and its 88 Earth day revolution period results in a two-orbit solar day.

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

Venus Reason: Yes. Note, however, that Venus's atmosphere is many, many times more dense.

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

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

Which of the following is true of Venus's crust?

Venus has a thick crust that holds heat

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.

Match the missions to Mars to their descriptions. Instructions

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

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

Volcanic mountains Continent-like masses Pancake domes

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

Wakes behind craters River valleys

How have we mapped the surface of Venus?

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

Typical weather conditions on Mars are ____.

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

Evidence that Mercury has a molten core includes ____.

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

The temperatures at Mercury's poles ____.

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

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

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

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

crater

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 Reason: Yes. Brightness goes as 1/2

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

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

lava domes

The search for life on Mars is concentrated on finding ____. (Choose all that apply.)

liquid water microscopic life

Mars's atmosphere is still steadily eroding due to charged particles from the Sun, because Mars doesn't have a strong enough _______________ field to deflect the solar wind.

magnetic

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

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

radar penetrating the thick clouds images capture by robotic landers

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

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 a _______ _______ effect.

runaway greenhouse

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

slow and retrograde; massive and dense

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

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 Reason: Angular size is inversely proportional to distance.

__________is Earth's closest neighbor that is so bright that if the air is very clear, you can sometimes find it in broad daylight.

venus

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

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

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