EXAM 2 Flashcards
What was the solar nebula?
A cold, slowly rotating cloud of gas and dust floating around in space
What was the solar nebula made of?
Dust, hydrogen, and other gases
How did gravitational collapse affect the Solar nebula?
As a nebula collapses into a protosolar disk, the disk spins faster and heats up from conservation of energy and conservation of angular momentum
How does conservation of energy and angular momentum affect solar system formation?
The temperature increased as the nebula collapsed (energy) and the solar nebula rotated faster and faster as it shrank in radius (angular momentum), directly causing the birth of the solar system and its orderly motions
What are the orderly motions of the planets?
All orbits are elliptical and circular, rotating in the same plane
All the planets revolve around the sun in a counterclockwise direction as seen from the North Pole star (Polaris)
The tilts of the axes are quite small but the planets rotate in the same direction as they orbit
What produced the orderly motion we observe in the solar system today?
A collapsing gas cloud naturally tends to heat up, spin faster, and flatten out as it shrinks in size. Thus, our solar system began as a spinning disk of gas. The orderly motions we observe today all came from the orderly motion of this spinning disk of gas
How do we explain the exceptions to the orderly motions?
Most of the exceptions probably arose from collisions or close encounters with leftover planetesimals, especially during the heavy bombardment that occurred early in the solar system’s history
What key fact explains why there are two types of planet?
Since different materials condense at different temperatures, our solar system formed different types of planets. The dividing line for the different planets in our solar system is called the frost line
What is the origin of asteroids and comets?
These small objects are leftovers from planetary accretion
How old is the Solar System and how do we know?
By studying several things, mostly meteorites, and using radioactive dating techniques, specifically looking at daughter isotopes, scientists have determined that the Solar System is 4.6 billion years old
What are chondrules?
Small, solidified droplets of molten early solar system material embedded in most stony meteorites
What is the frost line?
The zone in the Solar System far enough from the Sun where it is cold enough for ice to be stable
What are two ways to detect extra-solar planets?
Indirect observations (such as the Doppler technique, transits, and eclipses) are much more commonly used when searching for exoplanets. The Doppler technique is a good method for discovering exoplanets. It uses the Doppler effect to analyze the motion and properties of the star and planet
What is the Kepler mission?
Specifically designed to survey our region of the Milky Way galaxy to discover any planets, especially Earth-size and smaller planets, in or near the habitable zone and determine the fraction of the hundreds of billions of stars in our galaxy that might have such planets
How can we determine if an extra-solar planet has life?
The presence of oxygen in the atmosphere
Are Earth-sized planets common?
Based on an analysis of a large amount of astronomical data and with a high degree of confidence, that potentially habitable Earth-size planets around Sun-like stars are common.
Do most stars have planets?
Most stars have planets but exactly what proportion of stars have planets is uncertain because not all planets can yet be detected. That said it has been calculated that there is at least one planet on average per star
Describe the basic interior structures of the terrestrial worlds
Terrestrial planet interiors are composed of three basic parts: a dense, metallic core, a lower density solid mantle surrounding the core, and a solid outer shell called the crust. Jovian planets have a core and a fluid mantle that merges smoothly into their atmospheres
How do the interiors of terrestrial planets get hot?
In general, planets produce heat according to their size. Radioactive atoms decay in the interior, and conduction and convection transport this heat from the interior to the surface. Bigger planets have more gravity, and the pressure due to gravity helps to create a molten interior that can drive geological activity
What happens during planetary differentiation?
The separation of different constituents of planetary materials resulting in the formation of distinct compositional layers. Denser material tends to sink into the center and less dense material rises toward the surface, forming crusts
Why is planetary size so important to internal heat and geology?
Bigger planets have more gravity, and the pressure due to gravity helps to create a molten interior that can drive geological activity. Also, the bigger the planet, the longer it takes internal heat to reach the surface
What drives plate tectonics on Earth?
Convective flow in the mantle
What do continental collisions create on Earth?
Mountains and mountain ranges
How did the lunar maria form?
Large impacts fractures the Moon’s lithosphere, allowing lava to fill the impact basins
What was the composition of the original atmospheres of Earth, Venus, and Mars
Were all rich in water and carbon dioxide, with a minor contribution of molecular nitrogen
What evidence suggests a past warm and wet period on Mars?
Ancient river valley networks, deltas, and lakebeds
Is there water on Mars now? Where?
No liquid water (due to a lack of atmospheric pressure), but plenty in the form of ice in Mars’ polar caps
What causes deserts?
Weathering processes such as large variations in temperature between day and night put strains on the rocks, which consequently break in pieces. Although rain rarely occurs here there are occasional downpours that can result in flash floods
How many Hadley cells in the Earth’s atmosphere are there from the equator to the pole?
3 cells
Why don’t hurricanes form off the equatorial coast of South America?
Lack of Coriolis force
How do you use craters to determine the age of planetary surfaces?
More craters=older
Where did the CO2 in Earth’s original atmosphere go?
Locked up in sedimentary rocks, fossil fuels, absorbed by plants for photosynthesis, and dissolved in the oceans
Why isn’t there much erosion on Venus?
It’s rotation is too slow to produce weather, despite its thick atmosphere
What are the surfaces of Venus and Mercury composed of?
Both terrestrial planets made of rock and metal. Mercury is more dense than Venus and thought to consist of 60-70% metal, with the rest rock.
Is Venus still geologically active?
Probably
Why is Venus so hot?
Thick atmosphere with 90 bars of CO2
Compare the greenhouse effect on Venus, Earth, and Mars
Weak on Mars, Moderate on Earth, and very strong on Venus
How do gyres affect hurricanes?
Any large system of circulating ocean currents. In these, the heat would be taken away by subsurface currents, and so the surface would become cooler, leading to less intense hurricanes
How was the Moon created?
The giant-impact theory, which states that it formed during a collision between Earth and another small planet about the size of Mars.
What happened to the dinosaurs?
An asteroid the size of a mountain struck the coast of the Yucatán Peninsula, wiping them out
What creates global wind patterns?
Atmospheric heating at the equator creates two huge equator-to pole circulation cells. Depending on the strength of the Coriolis effect, the large cells may split into smaller cells. This occurs on Earth, but not Venus or Mars
Why are there deserts?
Hadley cells and lack of moisture in the air
How does rotation affect the creation of Hadley cells?
Earth’s rotation is responsible for the Coriolis effect which breaks the two large ones into 6 smaller ones
What are the gases in Earth’s atmosphere?
78% nitrogen and 21% oxygen with trace amounts of CO2, neon, and hydrogen
Why isn’t Florida a desert?
Essentially an island in a subtropical ocean, as long as winds come from the West, humid air will maintain our ecosystem
What are monsoons?
Seasonal change in the direction of the prevailing, or strongest, winds of a region. They cause wet and dry seasons throughout much of the tropics and are most often associated with the Indian Ocean
The Earth’s atmosphere is 21% oxygen. Was this always the case?
Early in Earth’s atmosphere it had very little oxygen and then at one point it had 35%
What is the difference between the atmospheres of Earth, Mars, and Venus?
Venus and Mars lack ultraviolet absorbing stratosphere
What are the major features of the Jovian planets?
Largely composed of hydrogen, helium, and hydrogen compounds. No solid surfaces with a fast rotation and slightly “squashed” shapes. Many moons and ring systems
Why are Jovian Planets so different from terrestrial planets?
Formed in cold, outer Solar System at the centers of “mini Solar nebulas”
What are the main elements of Jovian planet atmospheres?
They do not have solid surfaces and instead are primarily composed of hydrogen and helium, with traces of methane, ammonia, water, and other gases in their atmospheres
Do Jovian planets have Hadley cells?
No, they do not
What is the Great Red Spot?
A large and long-lived, possibly permanent storm on Jupiter
How do other Jovian atmospheres compare to Jupiter’s?
Atmospheric structures are similar but each is progressively colder with distance from the Sun. Saturn is the most similar to Jupiter. Uranus and Neptune are cold enough to have a methane cloud layer, which leads to their blue colors. Seasons play a major role on Uranus
Why can active geology occur on much smaller worlds when they are made of ice rather than rock?
Ices soften and melt at much lower temperatures than rock, allowing icy volcanism and tectonics at surprisingly low temperatures
Why do we suspect a subsurface ocean on Europa?
Due to geysers of water shooting out through cracks in the moon
Describe Saturn’s rings
Most extensive ring system of any planet in the Solar system. Consist of countless small particles ranging in size from micrometers to meters, that orbit around Saturn. The ring particles are made almost entirely of water ice, with a trace component of rocky material
How can planets migrate?
Once a planet has formed in the disk, the radius of its orbit can change due to gravitational forces between the planet and material in the disk. In this way, planets can migrate from their original location, a phenomenon that can explain the diversity of exoplanets
Which Jovian planets have ring systems?
All of them
What is the difference between a meteorite and meteor
A meteor is an object and burning through the atmosphere, a meteorite is on the ground
How do other ring systems compare to Saturn’s?
Massive ring system, which is the largest and brightest
What is the origin of planetary rings?
No one theory, and can result from a variety of processes like giant collisions, tidal stripping of comets or satellites, and planetary formation
How do you identify a meteorite?
Density and Magnetism
Why are so few meteorites found in Florida?
Florida’s moisture, salt air, humidity, and dense vegetation with regular rain
What are resonances in the asteroid belt?
A region in the belt where they experience strong gravitational perturbations by the planets, particularly Jupiter-that puts the meteoroids in Earth-crossing orbits
What is a Dwarf Planet?
A celestial body that orbits the sun, has enough mass to assume a nearly round shape, has not cleared the neighborhood around its orbit and is not a moon
What is the composition of comets?
Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices
What happens to a comet as it approaches the Sun?
Some of the ice starts to melt and boil off, along with particles of dust. This makes a cloud around the nucleus called a coma which is lit by the Sun, with the sunlight pushing the material into the brightly lit tail of the comet
What is the difference between a comet’s plasma tail and dust tail?
Plasma is caused by an interaction between the solar wind and cometary plasma while the dust tail is by the solar radiation pressure to the cometary dust
Why don’t Pluto and Neptune collide?
They’re moving at different speeds
Is Pluto a Kuiper belt object?
Yes
Do asteroid/comets still collide with Earth?
The probability of a major collision is small
