Astronomy Ch 10

Compare Mars with Mercury and the Moon in terms of overall properties. What are the main similarities and differences?

Mars is larger so it has atmosphere. Mars also has water The density of Mars and the internal or bulk composition is intermediate between the Moon and Mercury, with a metallic core and silicate mantle—

Why is Mars red?

Its surface rocks (iron) were rusted by oxygen.

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

On Earth, carbon dioxide is dissolved in oceans, but there are no oceans on Venus. Mars is smaller than Earth and Venus, so the escape velocity for carbon dioxide is smaller so its easier for gas to escape

Describe the current atmosphere on Mars. What evidence suggests that it must have been different in the past?

consists mostly of carbon dioxide, but is very thin, less than 1% of Earth's atmosphere. water on Mars in the past means that the atmosphere was thicker and warmer, or water would have evaporated away very quickly.

What evidence is there that Venus was volcanically active about 300-600 million years ago?

there are craters on Venus that are 300-600 million years old, and the surface has not changed so it was only active in that time

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

Venus and Mars water left atmosphere (evaporated in sun) or froze (on parts with no sunlight)

in what way is the high surface temperature of Venus relevant to concerns about global warming on Earth today?

Carbon dioxide increasing on earth could lead to similar conditions Venus in a long time due to greenhouse effect.

Contrast the mountains on Mars and Venus with those on Earth and the Moon.

Earth and Venus have extensive mountains of both a volcanic and tectonic origin but Venus has taller ones because it has less erosion. On Mars, all the large mountains are volcanoes, and on the Moon, the rings of mountains were produced by impacts. Mars has tallest because the smaller the planet the larger the mountains.

What evidence do we have that there was running (liquid) water on Mars in the past? What evidence is there for water coming out of the ground even today?

Images from orbiting spacecraft of runoff channels and outflow channels all show evidence of formation by running water. Several dry basins contain minerals that only form with water. dark streaks that got longer over the course of several days showed spectra of hydrated salts, and may be evidence of saltwater on Mars today.

What is a dust devil? Would you expect to feel more of a breeze from a dust devil on Mars or on Earth? Explain.

It is a whirlwind. Mars has thinner air so you would not feel the whirlwind as much as on earth

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 (radio waves) can penetrate Venus' planetary cloud cover. The same technique is used to map the surface of Earth for areas that are generally shrouded in clouds. radar mapping from orbit is more accurate at determining altitudes of features on Mars (but not necessary).

What is the composition of the polar caps on Mars?

Seasonal ice caps are made up of dry ice, or crystals of frozen carbon dioxide; the northern residual cap is water ice, the southern permanent ice cap is made predominantly of water ice with a covering of carbon dioxide ice.

How might Venus' atmosphere have evolved to its present state through a runaway greenhouse effect?

Sun evaporated water on Venus, releasing carbon dioxide. The carbon dioxide prevented infrared radiation from escaping the planet, leading to a rise in temperatures and of water and release of carbon dioxide. Sunlight would break up water vapor molecules higher in the atmosphere into hydrogen, which escaped the planet, and oxygen, which combined with surface rocks. The loss of water reduces the planet's ability to absorb carbon dioxide.

Near the martian equator, temperatures at the same spot can vary from an average of -135 °C at night to an average of 30 °C during the day. How can you explain such a wide difference in temperature compared to that on Earth?

The thin martian atmosphere does not shield the surface from sunlight during the day and does not retain heat to keep the surface warm at night.

Describe two anomalous features of the rotation of Venus and what might account for them.

Venus has retrograde rotation about its axis, opposite to the direction of spin of most other planets; its rotational period is longer than its orbital period, so its day is longer than its year. Venus collided with another large body that altered its orbit and rotation

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

Venus is too hot and dry for life. At just the time life was forming on Earth, the conditions on Mars were apparently rather similar so it could have had life (not today tho because of atmosphere.

Suppose that, decades from now, NASA is considering sending astronauts to Mars and Venus. In each case, describe what kind of protective gear they would have to carry, and what their chances for survival would be if their spacesuits ruptured.

Venus is too hot suit would have to be cooled but even then they would die. Mars would need pressure suit with air to match earth, heating systems, and protection from solar ultraviolet light. And thick enough to not be ruptured by dusty winds

List several ways that Venus, Earth, and Mars are similar

Venus, Earth, and Mars are similar in that they consist of rock and metal for the most part; they are terrestrial planets all have atmospheres and greenhouse effect All have volcanic activity

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

arth's atmosphere is about 4/5 nitrogen and 1/5 oxygen; Venus' atmosphere is mostly carbon dioxide, with a pressure about 90 times higher than Earth; Mars' atmosphere is also mostly carbon dioxide, with a pressure only about one hundredth that of Earth. Venus has had an ongoing runaway greenhouse effect, leading to extraordinarily high surface temperatures.

What is the composition of clouds on Mars?

dust clouds; water-ice, and frozen carbon dioxide crystals (dry ice).

Explain the runaway refrigerator effect and the role it may have played in the evolution of Mars.

gravity is not strong enough to hold a gaseous atmosphere, so the atmosphere would have gotten thinner as gas escaped. This would lead to lower temperatures, and more gas would have frozen and deposited out of the atmosphere, lowering temperatures still further. The thinner atmosphere and colder temperatures would lead to the loss of most water from the planet, except for water ice, and underground saltwater.

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? What might be some of the reasons for these differences?

the geology of Earth is dominated by plate tectonics, Venus has "blob tectonics," where the rising of hot material from within plays a dominant role in sculpting its surface. Venus is also different from Earth in having a much lower level of erosion, because no precipitation and surface wind speeds are very low.