Chp 11: mercury, venus, and mars

Suppose that all of venus's volcanic activity just stopped. How would this affect Venus's clouds? How would this affect the overall Venusian environment?

with the stop of volcanic activity, the atmosphere of Venus will no longer have substantial amounts of sulfur dioxide, sulfuric acid, and other sulfur compounds into the air. b) The clouds will decrease because Venusian clouds contain almost no water but high concentrations of sulfuric acid.

Why was it difficult to determine venus's surface temperature from earth? how was this finally determined?

Venus is covered with clouds, masking radiation directly from the surface, A black body curve was constructed based on measurements of microwaves

Explain two ways that the heat within Mars helped to maintain a greenhouse effect?

-- keep water vapor in gas form rather than falling to surface as condensation and stripping atmosphere of CO2 --keep UV light from penetrating the atmosphere and stripping it of its nitrogen (h20 and Co2 atmosphere thins)

What kind of surface features are found on Mercury? How do they compare to surface features on the moon? Why are they probably much older than most surface features on Earth?

-scarps -mountains -lava flows -craters Unlike the Moon, Mercury's surface has extensive low-lying plains. These areas probably have a similar origin to the lunar maria, which were produced almost 4 billion years ago. Primordial lava flows probably also explain the plains of Mercury. As large meteoroids punctured the planet's thin, newly formed crust, lava welled up from the molten interior to flood low-lying areas.

What is a dust devil? why would you feel much less breeze on Mars than on Earth:

1. Dust devil is a rising or traveling funnel of dust, dirt or sand. Because Martian dust is so fine, it can be carried aloft and spread over the surface by Martian winds even though the atmosphere is so tenuous. A wind on Mars is only about as strong as an Earth breeze.

Why does the atmospheric pressure on Mars vary with seasons? What is the relationship between this pressure and Martian dust storms?

1. Formation of snow removed gas from the atmosphere during winter, and lowered the atmospheric pressure across Mars. Later when spring came to the southern hemisphere, the dry-ice snow evaporated rapidly and the atmospheric pressure returned to its prewinter levels. The pressure dropped again in the southern hemisphere's summer, because it is then winter in the northern hemisphere, and dry-ice snow condenses at northern latitudes.

Why is it impossible to see Mercury or Venus in the sky at Midnight?

1. Mercury and Venus are both inferior planets whose orbits around the Sun are smaller than the Earth's. They appear after sunset over the western horizon and as a morning star before the Sun in the eastern sky. But they are impossible to see during midnight because it is between the Earth and the Sun.

What are the patterns of convection in the venusian atmosphere so different form those in our atmosphere?

1. On Venus, gases in the equatorial region are warmed by the Sun, then rise upward and travel in the upper cloud layer toward the cooler polar regions. The Earth's atmosphere has a more complicated convection pattern because the Earth's rotation, which is far more rapid than Venus's, distorts the convection cells.

How did the winds trick early observers of Mars into thinking that Mars had vegetation?

1. The Italian astronomer's observations of "channels" eventually became mistranslated into English as "canals." The alleged discovery of canals implied that there were intelligent creatures on Mars. The seasonal variations in color can be explained by winds in the Martian atmosphere that blow in different directions in seasons. Therefore, many Earth-based observers reported that dark areas on Mars had the greenish hue of vegetation. It turns out that this green color is from the motion of dust covering some parts of the Martian terrain.

How did the Mariner 2 not enter venus's atmosphere but determine that it contained little water vapor?

1. The Mariner 2 saw radiation that had been emitted by the planet's surface and then passed through the atmosphere like visible light through glass. By measuring the amount of radiation, astronomers concluded that the surface temperature of Venus was more than 400 degrees Celsius. Thus, they concluded that there cannot be any liquid water on its surface, for it is completely dry.

How was the Mars Oddessey space craft able to detect water beneath the Martian surface without landing on the planet?

1. The Mars Odyssey measured the cosmic rays hitting Mars to detect any water molecules, and found that there is abundant water beneath the surface at both Martian poles.

what is the martian crustal dichotomy? what is the evidence that the southern highlands are older than the norther lowlands?

1. The Martian crustal dichotomy is the process of dividing the sphere of Mars into two northern and southern hemispheres. The evidence that the southern highlands are older than northern lowlands is that the Martian crust is about 5 km thicker in the southern hemisphere than in the northern hemisphere.

Runaway greenhouse effect? Runaway icehouse effect?

1. a) Runaway greenhouse effect refers to an increase in temperature causing a further increase in temperature. b) Runaway icehouse effect refers to a decrease in temperature causing a further decrease in temperature.

What is 3-to-2 spin orbit coupling?

13-to-2 spin-orbit coupling explains that the planet makes three complete rotations on its axis for every two complete orbits around the Sun. The Sun's gravitational force on the near side of Mercury's long-axis is greater than the force on the far side. This tends to twist the long axis to point toward the Sun. Therefore, from one perihelion to the next, alternate sides of Mercury face the Sun. The Doppler Effect experiment proved this rotation to be true. (Mercury has a tidal bulge and points toward the Sun at perihelion where the Sun's gravitational pull is strongest.)

Viking Landers

1TExplhe Viking Landers may have failed to detect any biochemistry on Mars because the regolith has literally been sterilized. Hence, we cannot yet tell whether life ever existed on Mars, or whether it might yet exist elsewhere on or beneath the planet's surface.

What explanation has been offered for the unusual magnitude of Venus's rotation rate?

A large impact early in its history may have slowed Venus's rotation rate to its present value.

Why is it reasonable to assume that the primordial atmospheres of Earth, Venus, and Mars were roughly the same?

Atmospheres are thought to originate by outgassing throughvolcanoes. Because Venus, Earth,and Mars had extensive volcanism, it is reasonable to assumethat the primordial atmospheres ofthe planets were similar. However, each atmosphere evolvedin a unique way determined by theplanet's size and distance from the Sun.

How do craters reveal evidence for water-ice beneath the martian surface?

Just beneath crater impacts halfway between the North pole and equator, water is shown.

Larry Niven described 'the dark side" of mercury as the coldest place in the solar system. What assumption did he make about the rotation of mercury?

Larry Niven assumed that Mercury exhibited synchronous rotation with the Earth. However, Rolf B. Dyce and Gordon H. Pettengill proved using Doppler Effect that as Mercury rotates, one side of the planet approaches the Earth, while the other side recedes from the Earth.

Why is it best to view Mars near opposition?

Mars is closest to Earth when it is at opposition.--Because Mars's orbit is not circular, some oppositions find it closer to Earth than others.

Why do astronomers think Mercury has a very large iron core?

Mercury has a very high average density. The only abundant material with a high enough density to result in this average is iron. 1. Scientists believe that the higher uncompressed density means that Mercury has a larger proportion of iron than the Earth. Several other theories have been proposed to account for Mercury's high iron content. For example, one theory suggests that it was caused by a large planetesimal striking Mercury, or another theory stating that only iron-rich minerals could have condensed into solids with such high condensation temperatures.

Why can't you see any surface features on Mercury when it is closest to Earth?

Mercury is at inferior conjunction when it is closest to us. It is in "new" phase, and the surface is dark.

Describe the evidence of recent volcanic activity on Venus & Mars.

Most of the volcanoes on Venus are probably inactive at present, just as is the case with most volcanoes on Earth. However, the discovery of presence of such young lava flows suggests that Venus has some present-day volcanic activity. b) Unlike lava flows on Venus, most of the lava flows on Mars have impact craters on them. Most Martian lava flows are very old and that most of the volcanoes on the red planet are no longer active.

Explain discoveries of liquid water in relation to the Spirit and the Opportunity rover missions to mars.

Olivine and pyroxene break down if they are exposed to liquid water. But observing that they were still found among the sulfur salts, this proves that liquid water never existed in that area. b) The Opportunity discovered outcrops of sedimentary rocks on the plains of Sinus Meridianii. These rocks are heavily laden with sulfur compounds, strongly suggesting that they were produced by the evaporation of sulfur-rich water. It also found spheres of

What geologic features (or lack there of) on Mars have convinced scientists that that extensive plate tectonics did not significantly shape the present martian surface? Does Mars have any plates now?

One plate system: Mars lacks the global network of ridges and subduction zones that plate tectonics have produced on the Earth. Hence, the entire crust of Mars makes up a single tectonic plate.

Would a full Phobos or Deimos cast shadows on the martian surface? why or why not?

Phobos appears several times brighter in the Martian sky than Venus does from the Earth, while Deimos appears about as bright from Mars as Venus does from the Earth. These Martian moons are asteroids-- low density & low carbon content-- and would not reflect enough light to cast shadows

What magnetic features might indicate that Mars might have experienced plate tectonics in the past?

Presence of magnetic stripes that display alternating directions of magnetic fields in the crust... plate tectonics and magnetic dynamo are exhibited in this process

If Mercury is the closest planet to the sun and has such a high average surface temperature, how is it possible that ice might exist on its surface?

Radar observations detected patches at mercury's north and south poles that are unusually effective at reflecting radio waves. It has been suggested that these patches may be regions of water ice deep within craters where the Sun's rays never reach

Carbon dioxide accounts for about 95% of the present-day atmospheres of both Mars and Venus. Why, then, is there a strong greenhouse effect on Venus but only a weak greenhouse effect on Mars?

The atmosphere of Venus is many times denser than the atmosphere of Mars. There is not enough carbon dioxide on Mars to cause a significant greenhouse effect.

What is flake tectonics? Why does Venus exhibit flake tectonics rather than platetectonics?

The convection currents in Venus's interior are more vigorous than inside the Earth. The Venu-sian crust is much thinner than the continental crust on Earth. Rather than sliding around like theplates of the Earth's crust, the thin Venusian crust stays inroughly the same place but undergoeswrinkling and flaking.

What is the evidence that the surface of Venus is only about 500 million years old?

The evidence that Venus is only about 500 million years old is that there weren't too many craters found on Venus's surface. Venus was more heavily cratered in its youth, but localized activity in its crust has erased the older craters.

Is it surprising that mercury has a global magnetic field? What does a 58.646-day rotation period of Mercury imply that the planet can have only a weak magnetic field?

The existence of magnetic field on Mercury is a surprise because the cratered surface of Mercury shows evidence of a lack of geologic activity with no internal heat that powers such activity. But the existence of magnetic field shows that the planet has some internal heat left within its core. Mercury's very slow rotation of 58.646 days proves that Mercury can only have a weak magnetic field.-- Because Mercury's magnetic field is much weaker than that of the Earth, it is not able to capture particles from the solar wind. Therefore, it has no structures like the Van Allen belts that surround the Earth.

How do we know that the scarps on Mercury are younger than its lava flows? How can you tell that a scarp in figure 11-7 is younger than the vertically distorted crater at the center?

The scarps on Mercury's surface were probably formed as the planet cooled and contracted. And they must have formed relatively late in Mercury's history, after the lava flows had ended and after the planet had solidified to a substantial depth beneath the surface. On Figure 11-10, you can tell that the scarp is older than the crater because the floors of those craters were flooded by lava from the interior and they became distorted when the scarp formed.

Why is mars red? why is the color of a martian sky butterscotch?

The surface of Mars is very rich in iron oxides, and when it is exposed to sunlight, it creates the red-colored rust throughout the entire planet's surface. b) Mars appears to have a permanent haze of dust, which remains suspended in the air after duststorms. The dust is the mineral limonite, a brown iron oxide, the same mineral that forms most of the Martian surface. That is why the Martian sky is always a butterscotch tan color.

Do venus and mars have continents like those on earth?

The topographies of both Venus and Mars differ in important ways from that of our Earth. On Venus, 60% of terrain lies within 500m of the average elevation, while Mars has scattered continents among low-lying ocean floors. enus's continents compared to Earth's. Venus has two continents, Aphrodite Terra and Ishtar Terra. These continents are vertical displacements in Venus's relatively weak crust due to internal pressure. The crust of Venus is probably too thin to beak up into independent plates the way Earth's crust has. Thus, the Earth-like continents, formed by plate collisions or subductions are absent on Venus.

Explain why mercury does not have a substantial atmosphere.

There are two reasons for Mercury's lack of an atmosphere. First, because it is small and of low total mass, Mercury exerts a weak gravitational pull on any gases which might be bound to a more massive planet in a permanent atmosphere. Second, because Mercury is so close to the sun, its daytime temperatures are very high, about 800°F. Such high temperatures cause any gas molecules which might otherwise be gravitationally bound in an atmosphere to dance around so rapidly as to exceed Mercuriy's escape velocity, and therefore to escape!

Carbon Dioxide accounts for 95% of the present atmospheres of Mars and Venus, why then is there a strong greenhouse effect on venus and only a weak effect on Mars?

There is a stronger greenhouse effect on Venus because its intense sunlight gives a thick atmosphere, while Mars's weak gravity and feeble sunlight give it a thin atmosphere to have less greenhouse effect.

Why was it so difficult to determine the rate and direction of venus's rotation? How were these finally determined?

Venus is covered with clouds, so the observation of surface features is not possible. Doppler shifts from approaching and receding limbs were measured for radar waves (which can penetrate the cloud layer).

Compare the volcanos of venus, earth, and mars. Cite the evidence that hot-spot volcanism is or was active on all three worlds.

Volcanoes on Venus have gently sloping sides known as a shield volcano. Martian volcanoes are less numerous than those on Venus, but also shield volcanoes. Most volcanoes on Earth are found near the boundaries of tectonic plates, where subducted material becomes molten magma and rises upward to erupt from the surface.

Why is it impossible for liquid water to exist on Mars today/ if liquid water existed on mars in the past, what must have been different?

With the average surface temperature on Mars of 250 K and the pressure at 0.006 atmosphere, water can exist as a solid ice and as a gaseous water vapor, but never as a liquid. Hence, it never rains on Mars and there are no bodies of standing water anywhere on the planet.

The best time to observe Mercury without a telescope is when it is

at greatest eastern or western elongation and farthest from the Sun.