Astronomy Exam #3

What is the composition and structure of the Moon?

-Composition: 43% Oxygen, 20% Silicon, 19% Magnesium, 10% Iron, 3% Calcium, 3% Aluminum. ; Structure: Mean Density of 3,346.4 kg/m3 ; Composed of a distinct crust, mantle, and planetary core. -mostly silicate rock -The Moon has one-eightieth the mass of Earth and is severely depleted in both metals and volatile materials. It is made almost entirely of silicates like those in Earth's mantle and crust. However, more recent spacecraft have found evidence of a small amount of water near the lunar poles, most likely deposited by comet and asteroid impacts.

Compare the planetary evolution of Venus, Earth, and Mars.

-Earth: heat and gravity -Venus: gravity pulled swirling gas and dust together -Mars: gravity pulled swirling gas and dust in

Summarize the evidence for and against the possibility of life on Mars.

-If there was running water on Mars in the past, perhaps there was life as well. -The Viking landers searched for martian life in 1976, with negative results, but life might have flourished long ago.

Describe how impacts have influenced the evolution of life on Earth.

-Impacts by comets and asteroids represent the only mechanisms we know of that could cause truly global catastrophes and seriously influence the evolution of life all over the planet. -Larger past impacts are implicated in some mass extinctions

What is the general composition and structure of the atmosphere on Venus? How did the greenhouse effect lead to high temperatures on Venus?

-Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead.The atmosphere of Venus is the layer of gases surrounding Venus. It is composed primarily of carbon dioxide and is much denser and hotter than that of Earth. -A runaway greenhouse effect may have been caused by the evaporation of the surface water and subsequent rise of the levels of other greenhouse gases.

Provide an overview of the composition of the giant planets as summarize by the missions sent to the gas giants

-Jupiter and Saturn are more composed of gas -Uranus and Neptune are more composed of ice -These planets have been explored by the Pioneer, Voyager, Galileo, and Cassini spacecraft. Voyager 2, perhaps the most successful of all space-science missions, explored Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989)—a grand tour of the giant planets—and these flybys have been the only explorations to date of the ice giants Uranus and Neptune. The Galileo and Cassini missions were long-lived orbiters, and each also deployed an entry probe, one into Jupiter and one into Saturn's moon Titan.

What is the internal heat sources of each of the giant planets? How are they different?

-Jupiter and Saturn have major internal heat sources, obtaining as much (or more) energy from their interiors as by radiation from the Sun. Uranus has no measurable internal heat. Neptune has a small internal energy source -Uranus and Neptune are different from the other two planets

What are the characteristics of the giant planets' magnetic fields and how were they discovered?

-Jupiter has the strongest magnetic field and largest magnetosphere of any planet, first discovered by radio astronomers from observations of synchrotron radiation. -The magnetic fields of Saturn, Uranus, and Neptune, discovered by the spacecraft that first passed close to these planets. Inside each magnetosphere, charged particles spiral around in the magnetic field; as a result, they can be accelerated to high energies. These charged particles can come from the Sun or from the neighborhood of the planet itself. -Uranus and Neptune have even greater magnetic tilts, of 60° and 55°, respectively. -Saturn's magnetic field is perfectly aligned with its rotation axis.

What is the basic physical characteristics, general appearance, rotation, composition and structure of Jupiter, Saturn, Uranus, and Neptune?

-Jupiter is a colorful and dynamic planet, rotation:9 hours 56 minutes, composed primarily of hydrogen and helium, more than five times farther from the Sun than Earth's distance -Saturn twice as far away as Jupiter, rotation: 10 hours 40 minutes, composed primarily of hydrogen and helium. -Uranus orbits at 19 AU with a period of 84 years, see no obvious cloud layer at all, but only a deep and featureless haze, rotation periods of about 17 hours -Neptune, at 30 AU, requires 165 years for each circuit of the Sun, the upper clouds are made of methane,rotation periods of about 17 hours -All four have deep atmospheres and opaque clouds and core composed of heavier materials. -Uranus and Neptune are depleted in hydrogen and helium relative to Jupiter and Saturn -Each giant planet has a core of "ice" and "rock" of about 10 Earth masses

Name the major moons of each of the Jovian planets.

-Jupiter: Callisto, Ganymede, Europa, and Io -Saturn: Titan, Enceladus, -Uranus: Miranda, Ariel, Umbriel, Titania, Oberon -Neptune: Triton

What is the basic composition of each Jovian planet's ring system?

-Jupiter: tenuous ring of dust. -Saturn: the largest and is composed primarily of water ice. -Uranus: narrow ribbons of dark material with broad gaps in between. -Neptune: narrow and faint composed of dark materials and are thus not easy to see.

Compare tectonic activity and volcanoes on Venus with those of Earth.

-Like Earth, Venus is a planet that has experienced widespread volcanism. On both Earth and Venus, this upwelling lava can collect to produce bulges in the crust. Many of the granite mountain ranges on Earth, such as the Sierra Nevada in California, involve such subsurface volcanism. These bulges are common on Venus, where they produce large circular or oval features called coronae -On Venus' lowland plains, tectonic forces have broken the lava surface to create remarkable patterns of ridges and cracks. The planet has been modified by widespread tectonics driven by mantle convection, forming complex patterns of ridges and cracks and building high continental regions such as Ishtar.

What is the difference between rift and subduction zones?

-Plates pull apart along rift zones -Subduction: Two plates come together. Thinner ocean plate subducted under thicker continental plate

What are some distinguishing characteristics of Pluto's large moon Charon?

-Pluto also keeps its same face toward Charon. Like two dancers embracing, these two constantly face each other as they spin across the celestial dance floor. Astronomers call this a double tidal lock. -There are scattered craters in the lower part of the image, but much of the rest of the surface appears smooth. Crossing the center of the image is a belt of rough terrain, including what appear to be tectonic valleys, as if some forces had tried to split Charon apart. Topping off this strange image is a distinctly red polar cap, of unknown composition -shows evidence of geological activity. -in a retrograde orbit and has a diameter of about 1200 kilometers, more than half the size of Pluto itself. This makes Charon the moon whose size is the largest fraction of its parent planet

What are the primary types of rock that constitute Earth's crust?

-Sedimentary rocks: minerals deposited by wind or water. -Igneous rock:rock cooled from a molten state. -Metamorphic rocks: high temperature or pressure alters igneous or sedimentary rock physically or chemically -Primitive rock: the original material of the solar system.

Describe Mercury's structure and composition.

-Structure: Solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, deeper liquid core layer, and solid inner core. ; Composition: Huge iron core, Iron makes up 70% of Mercury's total weight. -Mercury's high density tells us that it must be composed largely of heavier materials such as metals

What features do we observe on the surface of Triton when Voyager 2 flew by?

-The Voyager flyby of Triton took place at a time when the moon's southern pole was tipped toward the Sun, allowing this part of the surface to enjoy a period of relative warmth(still cold basically). -the Voyager images showed that the evaporation of Triton's polar cap generates geysers or volcanic plumes of nitrogen gas

What are the general features of the surface of Venus? What do the study of craters on Venus tells us about the age of its surface?

-The more densely cratered the surface, the greater its age. The largest crater on Venus (called Mead) is 275 kilometers in diameter, slightly larger than the largest known terrestrial crater (Chicxulub), but much smaller than the lunar impact basins. -dominated by geologic features that include volcanoes, large impact craters, and aeolian erosion and sedimentation landforms.

Compare the major rings of Saturn and explain the role of the moon Enceladus in the formation of the E ring.

-a very faint, tenuous ring, called the E Ring, associated with Saturn's small icy moon Enceladus. The particles in the E Ring are very small and composed of water ice. Since such a tenuous cloud of ice crystals will tend to dissipate, the ongoing existence of the E Ring strongly suggests that it is being continually replenished by a source at Enceladus. -The ring particles are composed primarily of water ice, and they range from grains the size of sand up to house-sized boulders. An insider's view of the rings would probably resemble a bright cloud of floating snowflakes and hailstones, with a few snowballs and larger objects, many of them loose aggregates of smaller particles. In addition to the broad A, B, and C Rings, Saturn has a handful of very narrow rings no more than 100 kilometers wide. The most substantial of these, which lies just outside the A Ring, is called the F Ring.

What is the general composition of the atmosphere on Mars?

-atmosphere has a surface pressure of less than 0.01 bar and is 95% CO2. It has dust clouds, water clouds, and carbon dioxide (dry ice) clouds. Liquid water on the surface is not possible today, but there is subsurface permafrost at high latitudes.

What evidence has been discovered for the presence of water in the history of Mars?

-evidence has accumulated that rivers flowed on the red planet long ago. Two kinds of geological features appear to be remnants of ancient watercourses, both runoff channels and outflow channels. -Our rovers, exploring ancient lakebeds and places where sedimentary rock has formed, have found evidence for extensive surface water in the past.

Discuss the search for objects that could potentially collide with our planet.

Beginning in the 1990s, a few astronomers began to analyze the cosmic impact hazard and to persuade the government to support a search for potentially hazardous asteroids.

Describe the components of Earth's interior and explain how scientists determined its structure.

Components: The Core (Inner and Outer), The Mantle (Upper and Lower), and The Crust (Continental and Oceanic). ; Through the study of seismic waves.

Compare the basic physical properties of Earth, Mars, and Venus, including their orbits.

Earth: inner core, outer core, mesosphere, asthenosphere, and lithosphere.

Differentiate between Earth's various atmospheric layers and describe the chemical composition of our atmosphere.

Exosphere: Uppermost region of atmosphere, extremely thin air. ; Thermosphere: Second highest region of atmosphere, where ultraviolet radiation occurs. ; Mesosphere: Middle layer of the atmosphere, Air is too thin to absorb Earth's heat. ; Stratosphere: From the top of the troposphere to 31 miles above ground, contains the ozone. ; Troposphere: Lowest layer of atmosphere, contains all weather and clouds. ; Chemical Composition: 78% Nitrogen, 20% Oxygen, Mixture of small amounts of numerous other ingredients. -xray is 2, uv is 3, visible is 5

Describe the two theories of planetary ring formation.

First is the breakup hypothesis, which suggests that the rings are the remains of a shattered moon. A passing comet or asteroid might have collided with the moon, breaking it into pieces. Tidal forces then pulled the fragments apart, and they dispersed into a disk. The second hypothesis, which takes the reverse perspective, suggests that the rings are made of particles that were unable to come together to form a moon in the first place. (Rings are composed of vast numbers of individual particles orbiting so close to a planet that its gravitational forces could have broken larger pieces apart or kept small pieces from gathering together.)

Describe the causes and effects of the atmospheric greenhouse effect and global warming.

Greenhouse Effect: Caused by presence of water vapor, carbon dioxide, methane. Effects: Warms the Earth's surface. ; Global Warming: Causes: Accumulation of greenhouse gases as a result of fossil fuels. Effects: Warmer temperatures, melting poles, changes to ecosystems and environments.

Differentiate between the major surface features of the Moon.

Highlands: The lighter and heavily cratered regions of the moon. ; Lunar Mare: Large and dark basaltic plains. ; Impact Craters: Circular depressions in the surface.

Describe the major features we can observe and the geologic activity of each of the Galilean moons.

Jupiter's largest moons are Ganymede and Callisto, both low-density objects that are composed of more than half water ice. Callisto has an ancient cratered surface, while Ganymede shows evidence of extensive tectonic and volcanic activity, persisting until perhaps a billion years ago. Io and Europa are denser and smaller, each about the size of our Moon. Io is the most volcanically active object in the solar system. Various lines of evidence indicate that Europa has a global ocean of liquid water under a thick ice crust. Many scientists think that Europa may offer the most favorable environment in the solar system to search for life.

Describe the topography and features of Mercury's surface.

Mercury is similar to the Moon in having a heavily cratered surface and no atmosphere, but it differs in having a very large metal core

What is the relationship between Mercury's orbit and rotation?

Mercury rotates in a way that is unique in the Solar System. It is tidally locked with the Sun in a 3:2 spin-orbit resonance, meaning that relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun.

Describe the history of the lunar surface.

Moon was formed 4.5 billion years ago -> Volcanic plains erupted 3.3-3.8 billion years ago.

What have we learned from both manned and robotic lunar exploration?

Most of what we know about the Moon derives from the Apollo program, including 400 kilograms of lunar samples still being intensively studied.

How is ring structure affected by the presence of moons?

Much of our fascination with planetary rings is a result of their intricate structures, most of which owe their existence to the gravitational effect of moons, without which the rings would be flat and featureless. Indeed, it is becoming clear that without moons there would probably be no rings at all because, left to themselves, thin disks of small particles gradually spread and dissipate.

Describe information about Pluto's surface deduced from the New Horizons images

New Horizons image clearly shows the variety of terrains on Pluto. The dark area in the lower left is covered with impact craters, while the large light area in the center and lower right is a flat basin devoid of craters. The colors you see are somewhat enhanced to bring out subtle differences.

Why are impact craters less common on Earth compared with other planets and moons?

On Earth, impact craters are harder to recognize because of weathering and erosion of its surface.

What is the origin, size, and extent of Earth's magnetic field?

Origin: Generated by electric currents in the conductive iron alloys of Earth's core. ; Size: 65,000 Kilometers. ; Extent: 25-65 Microteslas.

Outline the origins and subsequent diversity of life on Earth.

Origins of Life: Fossilized Microorganisms that formed as early as 4.28 Billion Years ago. ; Biological Diversity: Different Plants, Animals, and Microorganisms.

How do the orbital characteristics of Pluto compare with those of the planets?

Pluto's orbit was more eccentric and inclined to the plane of our solar system than that of any other planet.

How do the rings of Uranus and Neptune differ in composition and appearance from the rings of Saturn?

Saturn's rings are broad, flat, and nearly continuous, except for a handful of gaps. The particles are mostly water ice, with typical dimensions of a few centimeters. The rings of Uranus are narrow ribbons separated by wide gaps and contain much less mass. Neptune's rings are similar but contain even less material.

Describe the top three early hypotheses of the formation of the Moon.

The fission theory—the Moon was once part of Earth, but somehow separated from it early in their history. The sister theory—the Moon formed together with (but independent of) Earth, as we believe many moons of the outer planets formed. The capture theory—the Moon formed elsewhere in the solar system and was captured by Earth.

How did a massive impact change the conditions for life on Earth, leading to the extinction of the dinosaurs?

The massive impact created an enormous ejection with amounts of dust, ash, and other materials into the atmosphere that blocked the Sun's radiation and drastically decreased Earth's temperature.

Summarize our ideas about the origin and evolution of Mercury.

The problem with understanding how Mercury formed is the reverse of the problem posed by the composition of the Moon. We have seen that, unlike the Moon, Mercury is composed mostly of metal.Early in its evolution, it apparently lost part of its silicate mantle, probably due to one or more giant impacts. Long scarps on its surface testify to a global compression of Mercury's crust during the past 4 billion years.

Explain the theory of plate tectonics.

The theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle.

How do tidal forces generate the geological activity we see on Europa and Io?

Tidal heating on Europa may have heated its interior enough to melt ice and produce a subsurface ocean. ; Tidal heating on Io produced volcanic activity.

Summarize the current "giant impact" concept of how the Moon formed.

envisions Earth being struck obliquely by an object approximately one-tenth Earth's mass—a "bullet" about the size of Mars. This is very nearly the largest impact Earth could experience without being shattered.Such an impact would disrupt much of Earth and eject a vast amount of material into space, releasing almost enough energy to break the planet apart. Computer simulations indicate that material totaling several percent of Earth's mass could be ejected in such an impact. Most of this material would be from the stony mantles of Earth and the impacting body, not from their metal cores. This ejected rock vapor then cooled and formed a ring of material orbiting Earth. It was this ring that ultimately condensed into the Moon.

How do crater counts to determine relative ages of lunar landforms?

it is possible to use the number of impact craters on its surface to estimate the age of that surface. By "age" here we mean the time since a major disturbance occurred on that surface (such as the volcanic eruptions that produced the lunar maria).

Why is the surface of Venus inhospitable to human life?

surface pressure of 90 bars and a temperature hot enough to melt lead and zinc.

What is the difference between weather and climate?

weather refers to short-term changes in the atmosphere, climate describes what the weather is like over a long period of time in a specific area. Different regions can have different climates.