Astronomy Final
The major processes that heat the interiors of the terrestrial worlds are
(1) Heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; and (3) heat released by radioactive decay
Asteroid Belt
- 400,000 chunks of rock and metal - Together smaller than the moon - Mainly between orbits of Mars and Jupiter
Jupiter
- 5 AU from sun - Mostly H/He, no solid surface - 300x more massive than Earth - Many moons, rings
Kuiper Belt
- Beyond Neptune's orbit - 100,000 objects - Pluto and other dwarf planets
Mars
- Earth-like - Giant volcanoes, canyons, polar caps - Water flowed in past, possible life
Saturn
- Giant and gaseous - Rings - Many moons - Rings are not solid: made of countless small chunks of ice and rock
Oort Cloud
- Huge, spherical region - Trillions of objects
Comets
- Icy, rocky, small objects - Some come close to sun and develop a tail
Moons of Jupiter/Galilean Moons
- Io: active volcanoes - Europa: possible subsurface ocean - Ganymede: largest moon in solar system - Callisto: large ice ball
Ganymede
- Largest moon in solar system - Evidence of geological activity - Tidal heating and radioactive decay
Terrestrial Planet Characteristics
- Mars is largest - Close to sun - Rock and metal - Solid surface - High density
The Sun
- Mostly Hydrogen and Helium - 99.9% mass of the solar system/brightest object
Jovian Planet Characteristics
- Much larger than terrestrials - Jupiter is largest - No solid surfaces - Hydrogen, Helium, and Hydrogen compounds - Farther from sun and farther apart - Low density - Rings and many mooons
Interiors of Jovian Planets
- No solid surface - Layers under high pressure and temp - Cores made of hydrogen compounds, metals, and rocks
Earth
- Oasis of life - Only surface liquid water in solar system - Large moon
Any theory of the formation of the Solar System should explain the following:
- Patterns of motion - Two types of planets: rocky inner and gaseous outer - Rocky asteroids and icy comets - Asteroid belt, Kuiper Belt, and Oort cloud
Geological Effects of Venus
- Radar mapping: atmosphere too thick - Cratering - Volcanoes - Erosion - Tectonics - Greenhouse effect: runaway
Exceptions of Solar System Theories
- Rotation of Venus - Retrograde moons - Earth's moon
Neptune
- Similar to Uranus (except for axis tilt) - Many moons (including Triton)
Mercury
- Size of moon - At least 1 moon - Made of metal and rock; large iron core - Very hot days and very cold nights
How did terrestrial planets form?
- Small particles of rock and metal were present inside the frost line - Planetesimals of rock and metal built up as these particles collided - Gravity eventually assembled these planetesimals into terrestrial planets
Uranus
- Smaller than Jupiter/Saturn, much larger than Earth - Made of H/He gas and hydrogen compounds - Extreme axis tilt - Moons and rings
Europa
- Tidal stresses crack surface ice - Tidal heating
Io
- Volcanic activity - Tidal heating - Orbital resonances - Most geologically active world in the solar system
Venus
- We can only see thick layers of sulfur clouds - Same size as Earth, less massive - Atmospheric pressure is 90x that of Earth - Extreme greenhouse effect - Even hotter than Mercury, 470 C day and night
How did the Jovian planets form?
-Ice could also form small particles outside the frost line - Larger planetesimals and planets were able to form - Gravity of these larger planets was able to draw in surrounding H and He gases
How long ago did the planets form?
4.5 billion years ago
Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of
A golf ball to a baseball
According to current evidence, Pluto is best described as
A large member of the Kuiper belt
Atmosphere
A layer of gas that surrounds a world
A terrestrial world's lithosphere is
A layer of relatively strong, rigid rock, encompassing the crust and part of the mantle
What is the Great Red Spot?
A long-lived, high-pressure storm on Jupiter
This graph shows the frequency of impacts on Earth by objects of various sizes. According to this graph, objects large enough to cause a mass extinction hit Earth
About once every 50 million years
Jovian Magnetospheres
All Jovian planets have one but Jupiter's is the largest by far - metallic hydrogen
Weather on Jovian Planets
All have strong winds and storms
Why is the sky blue?
Atmosphere scatters blue light from sun, making it appear to come from different directions - blue light scatters more than red
Venus has a higher average surface temperature than Mercury. Why?
Because its surface is heated by an extreme greenhouse effect produced by its substantial carbon dioxide atmosphere
Aurora
Charged particles from solar wind energize the upper atmosphere near magnetic poles, causing an aurora
Solar Wind
Constant flow of charged particles
Tectonics
Convection of the mantle creates stresses in the crust called tectonic forces
Which of the following best describes the internal layering of Jupiter, from the center outward?
Core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer
From center to surface, which of the following correctly lists the interior layers of a terrestrial world?
Core, mantle, crust
What is the largest terrestrial planet?
Earth
Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere
What would happen to Earth if we somehow moved our planet to the orbit of Venus?
Earth would suffer a runaway greenhouse effect and become as hot or hotter than Venus
Newton's Third Law
Every action has an equal and opposite reaction
Newton's First Law
Every object continues in its state of rest, or of uniform motion in a straight line unless compelled to change that state by forces impressed upon it
Flyby
Flies by another world only once
Newton's Second Law
Force = Mass x Acceleration
Orbiter
Goes into orbit around another world
Which internal heat source still generates heat within the terrestrial worlds today?
Heat from radioactive decay
From Nebula to Disk
Heating, spinning, flattening, and then disk
This painting shows a very large object colliding with Earth. What is thought to have happened as a result of this collision?
It blasted away debris that then accreted in Earth's orbit to form the Moon
What is the significance of this image?
It shows an actual disk of material orbiting another star, providing strong evidence the planets really do form in such disks
How does the strength of Jupiter's magnetic field compare to that of Earth's magnetic field?
Jupiter's magnetic field is about 20,000 times as strong as Earth's
Jovian Planets
Jupiter, Saturn, Uranus, Neptune
Probe/Lander
Lands on surface
Where did asteroids come from?
Leftover from the accretion process
This photograph was taken on the surface of another world in our solar system. What world is it?
Mars
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
Mars's interior has cooled so much that its molten core layer no longer undergoes convection
Angular Momentum
Mass x Velocity x Radius - Does not change under force of gravity
Terrestrial Planents
Mercury, Venus, Earth, Mars
The cores of the terrestrial worlds are made mostly of metal because
Metals sunk to the centers a long time ago when the interiors were molten throughout
The transit method searches for extrasolar planets by
Monitoring stars for slight dimming that might occur as unseen planets pass in front of them
Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is
Much larger
If we could put all the asteroids in the asteroid belt together, their total mass would be
Much less than the mass of Mercury
Most of the solar system's planets:
Orbit sun in the same direction, rotate in same direction as they orbit the sun
Gaps in the asteroid belt (often called Kirkwood gaps) are caused by
Orbital resonances with Jupiter
All the following statements are true. Which one makes it possible to learn of the existence of extrasolar planets without seeing the planets themselves?
Planets exert gravitational tugs on their stars that cause stars to orbit around the center of mass of their planetary systems
Gravitational Collapse
Regions of clouds compress due to shock waves produced by other stars, these regions collapse under their own gravity and stars eventually form
Sample Return Mission
Returns a sample of another world's surface to Earth
Mars has two moons that are most similar in character to
Small asteroids
Nebular Theory
States that our solar system formed from the gravitational collapse a giant interstellar gas cloud - the solar nebula
Great Red Spot
Storm on Jupiter that is twice as wide as Earth - Has existed for at least 3 centuries
Consider the following statement: "Rocky asteroids are found primarily in the asteroid belt and Kuiper belt, whereas icy comets are found primarily in the Oort cloud." What's wrong with this statement?
The Kuiper Belt contains icy comets, not rocky asteroids
Frost Line
The boundary in the solar nebula beyond which ices could condense; only metals and rocks could condense within the frost line
Radioactive Decay
The breakdown of a radioactive element, releasing particles and energy
What counts as an "exception to the rule" in being unusual for our solar system?
The diameter of Earth's moon is about 1/4 that of Earth
Which characteristic of Earth explains why we have an ultraviolet-absorbing stratosphere?
The existence of photosynthetic life
When you see the bright flash of a meteor, what are you actually seeing?
The glow of heated air surrounding a small particle as it burns up in our atmosphere
According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?
The jovian planets began from planetesimals made only of ice, whereas the terrestrial planets began from planetesimals made only of rock and metal
A large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why cloud spins faster as it shrinks in size?
The law of conservation of angular momentum
Which of the following best why we see horizontal "stripes" in photographs of Jupiter and Saturn?
The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds
This figure summarizes the geological histories of the terrestrial worlds. Based on this figure, what can you conclude?
The most important factor in a planet's geological history is its size
Outgassing
The process of releasing gases from a planetary interior, usually through volcanic eruptions
Law of Universal Gravitation
The scientific law that states that every object in the universe attracts every other object - Describes orbits of the planets and comets around the sun - Explains tides - Used to send rockets into space
This image shows Pluto photographed by the New Horizons spacecraft in 2015. What did scientists find most surprising when they saw this image?
The smooth areas and other features suggesting relatively recent geological activity
Inertia
The tendency of an object to resist a change in motion
Why are terrestrial planets denser than jovian planets?
The terrestrial planets formed in the inner solar nebula, where only dense materials could condense
Why does Jupiter have three distinct layers of clouds?
The three layers represent clouds made of gases that condense at different temperatures
Which of the following is not a general characteristic of the four jovian planets in our solar system?
They are higher in average density than are the terrestrial planets
Comets with orbits that take them through the inner solar system shed sand- to pebble-size particles that then follow the comet around its orbit. How do these particles affect Earth?
They are the particles that produce meteor showers
Which of the following best explain what we think happened to outgassed water vapor on Venus?
Ultraviolet light split the water molecules, and the hydrogen then escaped to space
Captured Moons
Unusual moons of some planets may be captured planetesimals
Greenhouse Effect
Visible light passes through the atmosphere and warms a planet's surface; atmosphere absorbs infrared light from surface, trapping heat
Which of the following is an example of convection?
Warm air expanding and rising, whereas cooler air contracts and fall
Origins of Earth's Water
Water may have come to Earth by way of icy planetesimals
Erosion
Weather-driven processes that break down or transport rock
Differentiation
When the planet is still very hot, heavier elements sink to the center and lighter elements float above
Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?
Your meteorite is a fragment from the core of a large asteroid that shattered in a collision