ASTR001-Quiz 3
Plate Tectonics. Typical motion of one plate to another is 1 centimeter per year. At this rate, how long would it take for two continents 3000 kilometers apart to collide? What are the global consequences of motion like this?
300000000 years This slight motion means that the entire surface of the Earth can change in a certain amount of time.
Briefly describe the basic atmospheric characteristics of each of the five terrestrial worlds.
Moon and Mercury have so little atmosphere they could be considered "airless" and have no wind or weather. Venus has a thick atmosphere mostly of carbon dioxide with uninhabitable hot and harsh environment. Mars has a carbon dioxide atmosphere but has air so thin you'd die within minutes Earth has a hospitable atmosphere with water, pressure, and temperature conductive to life.
What is the nebular theory, and why is it widely accepted by scientists today?
Nebular theory is the idea that the solar system formed from the gravitational collapse of an interstellar cloud of gas (or a nebula) and it is still widely accepted by scientists as it offers explanations for the four general features of out solar system and has continued to accrue scientific evidence supporting it.
What is outgassing and why is it so important to our existence?
Outgassing is when volcanos release gas during eruptions and gas escapes from volcanic vents. All the gas in our (and Venus' and Mars') atmosphere and the water that created Earth's oceans is a result of planetary outgassing.
What was the frost line? Which ingredients condensed inside and outside the frost line? What role did it play in the formation of two distinct types of planets?
The frost line is the line beyond which it is cold enough for hydrogen compounds to condense into ices. Rock and metals condense inside and beyond the frost line and hydrogen and helium never condense.
What is the greenhouse effect? Describe how is warms the planet.
The greenhouse effect works by temporarily trapping infrared light to keep surface temperatures in range. It warms the planet by slowing the escape of infrared radiation from the atmosphere.
Why do we think Triton is a captured moon? How might its capture be relevant to geological activity?
We think Triton is a captured moon because it orbits backwards and has high inclination on Neptune's equator. It's capture is relevant to geological activity as Triton is no longer heater but was at once and it has had recent geological activity even though it is in a bounded orbit around Neptune.
Size Comparisons: How many Earths could fit inside Jupiter (assuming you could fill up all the volume)? How many Jupiters could fit inside the Sun? The equation for the volume of a sphere is (4/3)(pi)r^2.
You could fit 1407.14 Earths inside Jupiter and 896.63 Jupiters inside the Sun
Radiometric Dating. You are dating rocks by their proportions of parent isotope potassium-40 (half-life=1.25 billion years) and daughter of isotope argon-40. Find the age of the following: a) A rock that contains equal amounts of potassium-40 and argon-40. b) A rock that contains three times as much argon-40 as potassium-40.
a) 0.5K+0.5Ar=1 Rock must be one half-life, 1.25 billion years old. b) Ar=3k 3K+K=1 K=1/4 Rock must be two half-lifes, 2.5 billion years old.
Spinning up the Solar Nebula. The orbital speed of the material in the solar nebula at Pluto's average distance from the Sun was about 5 km/s. What was the orbital speed of this material when it was 40,000 AU from the Sun (before it fell inward with the collapse of the nebula)? Use the conservation of angular momentum.
angular momentum=m*v*r=m*5km/s*40000 AU =0.000634Me
Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun? a) No b) Venus is the only exception c) Venus and Uranus are exceptions
b) Venus is the only exception
How do clouds contribute to Jupiter's colors? Why are Saturn's colors more subdued? Why are Uranus and Neptune blue?
As gas rises and condenses, the different types of gas condense and form clouds on Jupiter with ammonia creating the white clouds and the ammonium hydrosulfide creates brown and red clouds which make Jupiter look brown, red, and white. Saturn's colors are more subdued because less light penetrates to the depths at which Saturn's clouds are found and the reflected light is obscured by the atmosphere. Uranus and Neptune are blue because of their methane clouds that absorb red light which makes them appear blue.
What are asteroids? What are comets? Describe the basic differences between the two, and where we find them in our solar system.
Asteroids are made up of metal and rock and orbit in the asteroid belt between Mars and Jupiter. Comets are ice rich and found in the Kuiper belt beyond Neptune's orbit or in a distant spherical region called the Oort cloud.
Two Kinds of Planetesimals. Why are there two kinds of "leftovers" from solar system formation? List as many differences between comets and asteroids as you can.
Comets are planetesimals of the outer solar system made of ice and located in the Kuiper Belt or Oort Cloud. Asteroids are planetesimals of the inner solar system made of rock and located in the asteroid belt.
What do we mean by comparative planetology? Does it apply only to planets?
Comparative planetology is studying planets by comparing their similarities and differences which also includes moons, asteroids, and comets, in addition to planets.
Describe the core-mantle-crust structures of the terrestrial world, and how they imply differentiation. What is a lithosphere, and how does lithosphere thickness vary among the five terrestrial worlds?
Core is high-density materials at center, mantle is rocky moderately dense (of silicon and oxygen) surrounding the core, crust is lowest density rock (granite and basalt) forming outer skin. Less dense materials move up and dense materials move down causing differentiation. The lithosphere is the outer layer of cool rock. Earth and Venus have a thin lithosphere Moon and Mars have a very thick lithosphere Mercury has a thin lithosphere but it takes up 1/2 of its mantle
Why does Earth have a global magnetic field? Why don't the other terrestrial worlds have similarly strong magnetic fields?
Earth's charges particles within the molten of its liquid outer core and internal heat causes the liquid metal to rise and fall (through convection) while Earth's rotation twists and distorts the convection pattern so the electrons move around Earth's outer core like an electromagnet generating Earth's magnetic field. In order to have a magnetic field a terrestrial planet needs 1) An interior region of electrically conducting fluid (liquid or gas) like molten metal 2) Convection in the layer of the fluid 3) At least moderately rapid rotation. And none fill those requirements
Describe Earth's global wind patterns and the role of circulation cells. How does rotation affect these cells?
Earth's global wind patterns vary with latitude: equatorial wind blows from east to west, mid-latitude wings blow from west to east and high latitude winds blow like equatorial winds from east to west. The temperature of the locations of these wind patterns result in warm air being pushed to the poles and pushed cool air to the equator creating circulation cells. These circulation cells are not perfectly round flows due to Earth's rotation which is called the Coriolis Effect.
Describe each process by which atmospheres gain or lose gas. What factors control thermal escape?
Gain: -Outgassing is when volcanos release gases that have been trapped with the planet's surface. -Vaporization is when atmospheric gases condense then are vaporized into atmospheric gas -Surface ejection is when tiny impacts of micrometeorites knock individual atoms or molecules free from the surface Lose: -Condensation is when atmospheric gas is condensed into liquid states. -Chemical reactions that use gases as a component result in the loss of gas -Solar wind stripping is when particles from the solar wind strip away gas particles into space from a planet with no protective magnetosphere -Thermal escape is when a molecule of gas achieves escape velocity and flies into space. Size of planet (small=occurs more), proximity to the Sun (closer to the Sun=occurs more), and weight of gas (lightweight=occurs more) affect thermal radiation.
Summarize the processes by which planetary interiors get hot and cool off. Why do large planets retain internal heat longer than smaller planets?
Heating: -Accretion is the result of planetary contact which converts kinetic energy into thermal energy upon impact -Differentiation is when less dense material float up and denser materials move to the core converting gravitational potential energy into thermal energy through friction -Radioactive decay releases mass-energy with the atoms' nuclei which is converted into thermal energy Cooling: -Convection is when heat rises to cooler surface and cooler rocks fall into a mantle cell -Conduction carries heat through the lithosphere to the surface -Radiation cools as energy radiates into space Smaller planets have larger lithospheres making it more difficult for heat from the core to reach the surface, resulting in the thickening of the lithosphere containing convection to deeper layers until the planets cools.
Briefly summarize the geological history of the Moon. How did the lunar maria form?
Heavy cratering occurred about 4.4 billion years ago, then lava flows created volcanic plains 3-3.9 billion years ago, and heavy bombardment ended 4 billion years ago. The lunar maria formed when large bombardments occurred and these craters were filled by lava.
Describe the conveyor-like action of plate tectonics on Earth, and how it explains the differences between seafloor and continental crust.
Mid-ocean ridges occur where material rises up and creates a new seafloor crust, then makes its way across the ocean floor and is recycled into the mantle where the material is heated. The seafloor crust gets pushed into the mantle under the continental crust which forms a deep ocean trench. Continental crust does not get recycled back into the mantle.
Describe key features of Jupiter's four Galilean moons, and the role of tidal heating and orbital resonances in shaping these features.
Io is internally very hot with many volcanos. Although it should be cool, an internal heating process of tidal heating which arises from the effects of tidal forces exerted by Jupiter. As it orbits, Jupiter's tidal forces change on Io resulting in it being constantly flexed in different directions causing friction. Europa is covered in water ice with a warm core heated by weaker tidal heating than Io, but preventing any impact craters from showing. Europa also has a magnetic field. Ganymede is covered in a ice with warm water heated by radioactive decay heating and covering some craters. It also has a magnetic field. Callipso looked cratered and has no internal heat although it is suspected of having an ocean and has a magnetic field. Io, Europa, and Ganymede share an orbital resonance lining them up every 7 days and causing an elliptic orbital shape.
Two kinds of planets. The jovian planets differ from the terrestrial planets in a variety of ways. Using sentences that members of your family would understand, explain why the jovian planets differ from the terrestrial planets in each of the following: Composition, size, density, distance from the Sun, and number of satellites.
Jovian planets are gaseous (made up of metal, rock, and ice) and large in mass and size, far from the Sun and has many moons and satellites. Terrestrial planets are made up of metal and rock, small in mass and size, close to the Sun, and have few moons and no rings.
Briefly describe Jupiter's weather patterns. What is the Great Red Spot?
Jupiter exhibits the Coriolis Effect, but due to the speed of rotation the circulation cells split into many alternating bands of rising and falling air with wind speeds highest around the equator and all the boundaries between bands of rising and falling air. Occasionally, large storms interrupt Jupiter's wind patterns. The Great Red Spot is a giant storm somewhat like a hurricane while winds circulate in a high-pressure region region and its has been ongoing for 2 centuries.
Why does Jupiter have so much more internal heat? What generates internal heat on other jovian planets?
Jupiter is contracting causing such high internal heat. Saturn's heat is a result of differentiation due to helium rain. Neptune is also likely contracting, and Uranus emits essentially no excess internal energy (just as much as it receives from the Sun).
Why isn't liquid water stable on Mars today and why do we nontheless think it flowed on Mars in the distant past?
Liquid water is unstable because due to the temperature and pressure, water immediately evaporated or freezes into gas or solid states. We think there was once water on Mar due to the observations of eroded shorelines, and ended craters that look like they once edged crater lakes. There is also mineral evidence of water.
Disappearing Moon. Io loses about a ton (1000kg) of sulfur dioxide per second to Jupiter's atmosphere. a) At this rate, what fraction of its mass would Io lose in 4.5 billion years?
Lose 1.42x10^20 kg Io's mass= 8.93x10^22 It would lose 0.15% of Io's mass
Briefly explain why icy moons can have active geology at much smaller sizes than rocky worlds.
Since the icy moons were formed far from the Sun, they contain ices that can melt or deform at lower temperatures than rocky worlds, so even when they've cooled, they can still experience geological activity.
What is the solar wind, and what roles did it play in the early solar system?
Solar wind is a stream of charges particles continually blown outward in all directions from the Sun. In the early solar system, the solar wind cleared away the vast majority of hydrogen and helium gas in the solar nebular, preventing planets from accruing additional ice and changing its composition.
The Role of Reflectivity. By assuming 0% and 100% reflectivity (respectively), find the maximum and minimum temperatures for a planet at 1 AU. What reflectivity would be necessary to keep the average temperature exactly at the freezing point? Compare to Earth's actual reflectivity in Table 10.2.
T=280K[(1-reflectivity)/d^2]^(1/4) [0%] 280 K [100%] 0K 9.4% reflectivity would result in the planet staying at freezing point
What are the basic differences between terrestrial and jovian planets? Which planets fall into each group?
Terrestrial planets are small in mass and size, are close to the Sun, are made up of metal and rock, and tend to have few moons and no rings. Mercury, Venus, Earth, and Mars are terrestrial planets. Jovian planets are large in mass and size, are far from the Sun, are made of hydrogen and helium compounds, and have rings and many moons. Saturn and Uranus are Jovian planets.
What is a magnetosphere? Describe its role in protecting any atmosphere form the solar wind and in creating auroras.
The magnetosphere is a strong magnetic field surrounding Earth that acts as a protective bubble from solar winds. The magnetosphere deflects the particles of the solar wind, except for the few that get through in the poles which move along the magnetic field lines in charged particle belts, and charged particles trapped in the magnetosphere create light auroras when particles collide within the atmosphere.
Briefly describe the patterns of motion that we observe among the planets and moons of our solar system.
The planets in the solar system orbit clockwise around the Sun and the Sun rotates clockwise. All planets rotate clockwise except for Venus and Uranus which move counterclockwise. The moons of the planets orbit in the direction that their planets rotate.
Why is the sky blue? Why are sunrises and sunsets red?
The sky is blue because gas molecules scatter high energy blue light more effectively than lower energy light so that only blue light gets scatter thus blue light reaches our eyes from all directions. At sunrise and sunset, sunlight has to travel through more atmosphere resulting in the blue light getting scattered away leaving only red light to color the sky.
Describe the atmosphere and surface features of Titan. How is Titan's landscape similar to Earth's? How is it different?
Titan's atmosphere is so thick, visible light cannot pass through and it is mostly nitrogen, but has normal pressure and is extremely cold. The climate is wet, but with methane instead of water. Titan is like the Earth's desert southwest where infrequent rainfall results in water evaporating or sinking into the ground.
Asteroid Orbit. Ceres, the largest asteroid, has an orbital semimajor axis of 2.77 AU. Use Kepler's third law to find its orbital period. Compare your answer with the value in Table 7.1 and name the planets that orbit just inside and outside Ceres' orbit.
p^2=a^3 p=4.61 years Mars, Venus, Earth and Mercury orbit inside Ceres' orbit and Jupiter, Saturn, Uranus, Neptune, and Pluto and other dwarf planets orbit outside Ceres' orbit.
Collapsing Cloud. The time it takes for a cloud 100,000 AU in radius to collapse in "free fall" to form a new star is half the time it would take an object to orbit the star on an extremely elliptical orbit with a semimajor axis of 50,000 AU. Use Kepler's third law to find the collapse time, assuming the star has the same mass as the Sun.
p^2=a^3 p^2=125,000,000,000,000 p=11,180,339.89 years
