Astronomy Week 10

Based on what you learned about Venus, select all of the correct statements from the following list.

Due to being closer to the sun and therefore slightly hotter than Earth when it first formed, Venus' water vapor could not condense to form oceans. This lack of carbon dioxide-absorbing liquid water has caused Venus to sufferer a runaway greenhouse effect;

In size and mass, Venus is very similar to Earth;

Venus' atmosphere is much thicker than Earth's, and much hotter.

Based on what you learned about Mars and its moons, select all of the correct statements from the following list.

Mars has polar ice caps;

Mars seems to have been much more Earth-like in the past;

Mars' moons are most likely captured;

Mars is smaller than Earth and Venus, but bigger than Earth's moon;

Very large canyons and volcanoes show us that Mars is geologically active.

*couldn't get this question exactly right

Why might we expect Venus and Earth to be similar?

Both planets are about the same size, density, and have the same chemical composition.

Which gas is most abundant in the atmospheres of Venus and Mars?

carbon dioxide (CO2)

In these two radar-generated maps of the surface of Venus, you can see that the geology of Venus is dominated by which of the following?

volcanism

Measurements from orbiting spacecraft suggests that Mars had a magnetic field in its past. How could Mars lose its magnetic field?

Mars has cooled to the point that it no longer has a fluid interior.

What evidence do we have that Mars had much more liquid water at its surface in the past than it has today?

The deuterium-hydrogen ratio is 5.5 times as high as on Earth; Martian meteorites must have formed from lava that was up to 1.8% water; We see large, dry outflow channels and valley networks on the surface of Mars; and The deuterium-hydrogen ratio is 5.5 times as high as on Earth and Martian meteorites must have formed from lava that was up to 1.8% water.

The layered rock and spherical concretions seen here are evidence that water once flowed on the surface of which of the following?

Mars

List several ways that Venus, Earth, and Mars are similar. (Select all that apply.)

All three are composed mostly of rock and metal; All three are terrestrial planets; All three have atmospheres; All three have volcanic activity on their surfaces.

List several ways that they are different. (Select all that apply.)

Only Earth has liquid water on it's surface; All three undergo large-scale surface changes through the different mechanisms.

Compare the current atmospheres of Earth, Venus, and Mars in terms of composition.

Earth's atmosphere is composed mostly of nitrogen and oxygen, while Venus and Mars have atmospheres that are mostly carbon dioxide.

Compare the current atmospheres of Earth, Venus, and Mars in terms of thickness (and pressure at the surface).

Venus has the thickest atmosphere, while Mars has the thinnest.

Compare the current atmospheres of Earth, Venus, and Mars in terms of the greenhouse effect.

Venus has an ongoing runaway greenhouse effect, while Mars has a runaway refrigerator effect. The Earth is currently seeing an increase in the greenhouse effect.

Venus and Earth are nearly the same size and distance from the Sun. What are the main differences in the geology of the two planets? (Select all that apply.)

What might be some of the reasons for these differences?

Earth experiences significantly more erosion than Venus; Only Earth appears to experience plate tectonics.

There is no precipitation or high winds on Venus, meaning there is a lot less erosion on the planet than there is on Earth.

Which is something that Venus and Earth have in common?

size, mass, and surface gravity

Which is something about Venus and Earth that is different?

surface temperature, atmospheric pressure, and atmospheric composition

What evidence can you give that Venus once had more water than it does now?

Where did that water come from?

Where did it go?

the relatively large abundance of deuterium in the atmosphere

It came from volcanic degassing.

It was broken up by ultraviolet radiation from the Sun.

Why doesn't Mars have folded mountain ranges like the ones on Earth?

The tectonic processes that formed mountains on Earth did not occur on Mars.

Why doesn't Earth have large volcanoes like those on Mars?

Tectonics carries mountains away from volcanic hot spots before they can grow too big.

What were the canals on Mars eventually found to be?

How do they differ from the outflow channels and valley networks on Mars?

optical illusions

The outflow channels and valley networks really exist, while the canals do not.

Propose an explanation for the nearly pure carbon dioxide atmospheres of Venus and Mars. (Select all that apply.)

Why is Earth's atmosphere different?

As Venus and Mars lost most of the liquid water they initially had, carbon dioxide was not dissolved in the water and thus not converted to sediments, and therefore it stayed in the atmosphere;

Carbon dioxide was probably released from molten rocks during lava flows, or it could have been produced when rocks were melted when many meteorites struck the surfaces of Venus and Mars.

Earth has liquid water, which dissolved much of its initial carbon dioxide and converted it to sediments like limestone.

Rank the planets Earth, Venus, and Mars in the following orders.

(a) decreasing size

(b) increasing mass

(c) decreasing number of moons

(a) Earth, Venus, Mars

(b) Mars, Venus, Earth

(c) Mars, Earth, Venus

Rank the planets Earth, Venus, and Mars in the following order.

(a) increasing distance from the sun

(b) decreasing surface temperature

(c) increasing atmosphere pressure

(a) Venus, Earth, Mars

(b) Venus, Earth, Mars

(c) Mars, Earth, Venus

Evidence suggests that Mars had a greater abundance of atmospheric carbon dioxide in the past than it has today. How could Mars have lost some of its atmospheric carbon dioxide?

Some carbon dioxide solidified and is part of the polar ice caps and the solar wind can ionize and strip gas molecules from the upper atmosphere.

What are the advantages of using radar imaging rather than ordinary cameras to study the topography of Venus?

What are the relative advantages of these two approaches to mapping Earth or Mars?

Radar imaging allow scientists to better view the surface of Venus.

This strategy is useful for mapping Earth, but not Mars.

Why is there so much more carbon dioxide in the atmosphere of Venus than in that of Earth?

The carbon dioxide on Earth dissolved in the ocean water and is now found in sea sediments.

Why is there so much more carbon dioxide in the atmosphere of Venus than in that of Mars?

The escape velocity for carbon dioxide on Mars is smaller than on Venus.

Compare Mars with Mercury and the Moon in terms of overall properties. What are the main similarities and differences? (Select all that apply.)

Mars is more dense than the Moon, but less dense than Mercury;

All three have a significant amount of frozen water at their poles;

Unlike the Moon and Mercury, Mars has both a metallic core and a silicate mantle.

*couldn't get this question exactly right

Is it likely that life ever existed on either Venus or Mars? Justify your answer in each case.

The conditions on Venus have always been too hot and dry for life, but Mars was once wetter and warmer, and may have harbored life several billion years ago.

We believe that Venus, Earth, and Mars all started with a significant supply of water. Explain where that water is now for each planet.

for Venus...

for Earth...

for Mars...

mostly lost into space

mostly in oceans and ice fields

mostly in permafrost and polar caps

The process by which Venus became so much hotter than the Earth is called _____.

the runaway greenhouse effect

One of the most impressive features of the geology of Mars is an uplifted area about the size of North America, with volcanoes on it, which is called the _____.

Tharsis Bulge

The largest volcano on Mars is called _____.

Olympus Mons (Mt. Olympus)

Valles Marineris is a wide, deep network of chasms stretching for some 2500 miles on the surface of Mars. How do we believe such a big set of canyons formed originally?

it was caused by tectonic pressures from deep within the planet

What makes astronomers believe that Mars once had rivers and running water?

images from orbiting spacecraft reveal ancient channels that look like dried-up river beds on Earth (and our rovers show geological formations made by running water)