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ASTR103 - Sun, Mercury, Venus, Earth, Mars

Test 2 - Topics on Weeks 1 - 10; emphasis on Weeks 6 - 10.
SUN - Three layers
SUN - Photosphere
Bright visible surface of the sun. It is a thin layer of gas from which Earth receives most of the sun's light.
SUN - Chromosphere
Visible just above the photosphere, is a thin layer of bright gas
SUN - Corona
Sun's faint outer atmosphere
SUN - Convection
Occurs when hot fluid rises and cool fluid sinks
SUN - Solar wind
Gas flows away from the sun in a breeze.
Pass Earth at 300 to 800 km/s, with gusts as high as 1000 km/s.
SUN - Positron (e+)
Particle emitted when two hydrogen nuclei (two protons) combine
SUN - Neutrino (v)
Subatomic particle having an extremely low mass and a velocity nearly equal to the velocity of light
SUN - Deuterium
Heavy hydrogen nucleus
SUN - Convective zone
Packet of energy is carried outward as circulating gas. Rising hot gas carries energy outward but sinking cool gas is a necessary part of the cycle that results in the net transport of energy outward.
SUN - Sunspots
Cool spots on the sun's surface caused by strong magnetic fields.
SUN - Sunspot cycle
11-year cycle becoming more numerous, reaching a maximum and then becoming much less numerous
SUN - Zeeman effect
Gives astronomers a way to measure the strength of magnetic fields on the sun and provide evidence that sunspots contain strong magnetic fields.
SUN - Affects of sunspots on Earth's climate
Intensity of sunspots cycle can very from cycle to cycle and appears to have almost faded away during the Maunder minimum (late century). Seems to have affected Earth's climate.
SUN - Active regions
Evidence is clear that sunspots are part of this region dominated by magnetic fields that involve all layers of the sun's atmosphere
SUN - Dynamo effect
When an electrical conductor rotates and is stirred by convection, it can convert some of the energy flowing outward as convection into a magnetic field.
SUN - Solar activity
Activity is magnetic.
SUN - Prominences
Arched shapes of solar activity produced by magnetic fields. When two arches encounter each other a reconnection can release powerful eruptions called flares.
SUN - Filaments
Prominences seen from above
SUN - Flares
Tremendous energy can be stored in arches of magnetic field when two arches encounter each other a reconnection can release powerful eruptions
SUN - Coronal Mass Ejections
CMEs can trigger communications blackouts and auroras
SUN - Coronal holes
In some regions of the solar surface, the magnetic field does not loop back. these high-energy gases from this area of the sun flows outward and produces much of the solar wind.
Innermost planet in the solar system
Passes through phases like the moon and Venus
MERCURY - Rotation
Tidally coupled with Sun
Rotating period - 59 days
Orbital period - 88 days
Period of rotation is 2/3 its orbital period
MERCURY - Resonance
Slowed rotation and coupled its rotation to its revolution
MERCURY - Surface
Temperatures extreme related to proximity to Sun
Daytime temps can exceed 700 K (800 F); 500 K is usual high temps
Shadow/night temps cool to 100K (-280 F) due to no atmosphere
Looks like Earth's moon
Uniform gray
MERCURY - Lobate scarps
Great curved cliffs found on Mercury
As high as 3 km and reach hundreds of km across surface. Believed to have been produced by tidal stresses generated when sun slowed Mercury's rotation.
MERCURY - Plains
Mercury has two different kinds of plains; Intercrater and smooth.
MERCURY - Intercrater plains
Less heavily cratered areas on Mercury. Marked by meteorite crates less than 15 km in diamter and secondary craters produced by chunks of ejecta from larger impacts. Plains are not saturated by craters.
MERCURY - Smooth plains
Smaller region on Mercury appear to be younger than the intercrater plains. They have fewer craters and appear to be lava flows that occurred after most cratering had ended.
MERCURY - Interior
Large metallic core
60% denser than Moon
Impact theory explains the small planet size and dense world with an unusually large core
Venus is a twin to Earth (size, density, composition)
Covered by thick clouds preventing observations from earth
Dry and hot surface
Very slow rotation (243 Earth days to rotate once)
Retrograde (backward) direction
VENUS - Atmosphere
96% carbon dioxide; 3.5% Nitrogen; .5% Water Vapor (Sulfuric Acid, Hydrochloric acid, Hydrofluoric acid)
Thick cloud made up of sulfuric acid droplets an microscopic sulfur crystals
Clouds much higher and more stable than Earth's
Cool upper atmosphere
Hot lower atmosphere
VENUS - Atmospheric circulation
Highly stable
Rotates in 4 days
Planetwide wind patterns
Believed to be related to the planet's slow rotation
VENUS - Surface
470 C/880 F temp
Atmospheric pressure 90 times than Earth's
No ozone layer
Once had significant amounts of water
Mountains, plains and some craters
VENUS - Greenhouse
Carbon dioxide is transparent to light but opaque to infrared heat radiation. For this reason, Venus' surface is hotter than Mercury. Since Venus has no significant amount of water now, the carbon dioxide isn't absorbed.
VENUS - Volcanism
Volcanoes on Venus are shield volcanoes produced by hot-spot volcanism and not by plate tectonics.
Large size volcanoes due to repeated eruptions at the same place in the crust.
VENUS - Coronae
Circular bulges up to 2100 km in diameter containing volcanic peaks and lava flow. Appear to be caused by rising currents of molten magma below the crust that create an uplifted dome and then withdraw to allow the surface to subside and fracture.
VENUS - Rotation
Nearly all planets in our solar s
ystem rotate counter-clockwise (as seen from the north). Uranus and Venus are the exception.
VENUS - History
It is believed that Venus does not have a magnetic field and is therefore unable to protect itself from solar winds.
Intermediate size terrestrial planet. Twice diameter moon, little more than half Earth's diameter. Smaller sized caused it to cool faster than Earth. Most of the atmosphere has leaked away and it's carbon dioxide atmosphere is less than 1% as dense as Earth's.
MARS - Canals
Martian day approximately 24 hrs 40 mins, axis tipped 25.2 degrees, has seasons about the same as winter/summer contrast as Earth. Based on ancient observations, it was believed that intelligent life forms lived on Mars due to what appeared to look like canals on the planet. However, these "canals" are actually optical illusions.
MARS - Atmosphere
95% of air on Mars is Carbon dioxide; few % of Nitrogen and Argon. (Similar to Venus)
Reddish color of Martian soil is caused by iron oxides (rusts).
Contains almost no water vapor or oxygen
Density about 1% of Earth's
Water can exist in Mars only as ice or vapor
Winds are strong enough to produce dust storms that envelope entire planet
Polar caps are frozen carbon dioxide ("dry ice") with frozen water underneath
MARS - Geology
Nights are deadly cold but hot summer days are comfortable.
Weather, complex geology, and signs that water once flowed surface
Mars is divided into two parts: Southern highlands and Northern lowlands
MARS - Southern highland
Heavily cratered, number of craters show they are old
MARS - Northern lowlands
Smooth and free of craters that they must have been resurfaced no more than a billion years ago. Scientist believe volcanic floods filled the northern lowlands ad buried craters. Evidence suggest this region were once filled by an ocean of liquid water.
MARS - Volcanoes
Volcanoes on Mars are shield volcanoes that form over hot spots of rising magma below the crust. The largest volcano in the solar system is on Mars called Olympus mons
MARS - Water
Evidence shows there was once water on Mars. it can not exist in the current conditions because it would evaporate in the atmosphere.
MARS - Outflow channels
Appear to have been cut by massive floods carrying 10,000 time more water than the Mississippi River
MARS - Valley networks
Look like meandering riverbeds that may have formed over long periods of time. Located in the old, cratered, southern hemisphere and are very old.
MARS - History
Most of the activity of Mars creation happened in the first part of total existence; three periods - Noachian, Hesperian, Amazonian
MARS - Noachian period
From formation until 3.7 billion years ago
Crust battered during heavy bombardment
Flooding by great lava flows, smoothed some regions
Volcanism active in Tharsis and Elysium regions
Valley networks formed during this period
when water fell as rain or snow
Oceans or lake may have formed during this period; however we don't know how long they existed
MARS - Hesperian period
Extended from 3.7 billion years ago to 3 billion years ago
Massive lava flows covered some regions
Most of outflow channels date from this period
Suggests the loss of atmosphere drove Mars to become deadly desert world with water frozen in its crust
Volcanic heat or lg impacts melted subsurface ice, water could have produced violent flooding and shaped the outflow channels
MARS - Amazonian period
From 3 billion years ago to present
Planet has lost much of internal heat
Core no longer generates magnetic field
Crust is too thick to be active with plate tectonics, hence no folded mountains
MARS - Moons
Mars has two moons believed to have been asteroids that were captured.
Named Deimos and Phobos shaped like potatoes.
Low density
Heavily cratered
MARS - Moons 3 principles of comparative planetology
1-Some satellites are probably captured asteroids
2-Small satellites tend to be irregular in shape and heavily cratered
3-Tidal forces can affect small moons and gradually change their orbits
EARTH - 4 stages of planetary formation
EARTH - Differentiation
Separation of material according to density
EARTH - Cratering
Can not begin until solid surface is formed
Phase happens during heavy bombardment
EARTH - Flooding
Radioactive decay continue to heat interior and caused rock to melt in the upper mantle, the molten welled up through rocks and flooded basins with lava then with water to form today's oceans
EARTH - Evolution
Has continued for the past 3.5 billion years
does not stop due to plate tectonics and erosion
EARTH - Unique qualities
1 - Abundant amounts of water
2 - Presence of life
EARTH - Water
Covers 75% of surface, no other planet in solar system has this element on the surface. Rare material in most planets.
EARTH - Life
No evidence of this on other planets in the solar system. Humankind actively altering our planet.
EARTH - Interior
Information about the make up of the earth is studied through seismic waves measured during earthquakes; look at Pressure P Waves and Shear S Waves. Information confirm that interior consists of three parts: Central core, thick mantle, thin crust.
EARTH - Pressure P Wave
Travel as a sequence of compressions and decompressions. As waves passes, particles of matter vibrate back and forth parallel to the direction of wave travel.
EARTH - Shear S Wave
Waves move as displacements of particles perpendicular to the wave's direction of travel. Waves distort the material but do not compress it.
EARTH - Core
S waves prove the core is mostly liquid with the size being approx 55% of Earth's radius. Mathematical models predict the core is hot (6000 K); dense ( 14g/cm^3) and composed of iron and nickel. Inner core is solid and is about 22% of Earth
EARTH - Mantle
Seismic data shows the mantle is not molten but not solid either, it behaves like plastic (material with properties of a solid but capable of flowing under pressure. Mantle is most plastic just below the crust
EARTH - Crust
Rocky crust is made up of low-density rocks and floats on the denser mantle. Crust is thickest under the oceans, where it is only about 10 km thick. Crust is brittle and can break when it is stressed.
EARTH - Magnetic field
Magnetic field direct result of its rapid rotation and its molten metallic core. Internal heat forces the liquid core to circulate with convection while Earth's rotation turns it about an axis. Core is highly conductive iron-nickel alloy. Process called dynamo effect, same process that generates solar magnetic field in the convective layers of the sun.
Protects from solar wind by deflecting it
EARTH - Active Crust
Motion of crust and erosive action of water makes Earth's crust highly active.
Plate tectonics - motion of crustal plates - produces much of geological activity on Earth.
Continents of Earth have moved - where one land mass at one point, have separated into the different continents of today.
Most of geological features of today are recent products of Earth's active surface.
EARTH - Atmosphere
It is believed that Earth formed very rapidly and went straight to a secondary atmosphere (volcanic) and never had a hydrogen-rich primeval atmosphere.
EARTH - Early atmosphere (carbon dioxide)
As the early atmosphere cooled, the water condensed to form the first oceans. Carbon dioxide is easily soluble in water and the first oceans began to absorb atmospheric carbon dioxide. Once in solution, carbon dioxide reacted with dissolved substances in the sea water to form mineral sediments in the ocean floor, freeing the seawater to absorb more carbon dioxide.
EARTH - Early atmosphere (oxygen)
When Earth was young, its atmosphere had no free oxygen (not combined with other elements). Oxygen is reactive and quickly forms oxides in soil and other substances dissolved in water. Only action of plant life keeps a steady supply of oxygen in Earth's atmosphere via photosynthesis which makes energy for plants by absorbing carbon dioxide and releasing oxygen. There is oxygen on Earth's atmosphere because of life (not the other way around).
EARTH - Ozone layer
Earth's lower atmosphere is not protected from ultraviolet radiation by a layer about 15-30 km above surface that exists because the atmosphere contains abundant ordinary oxygen from which the ozone is made.
EARTH - Greenhouse effect
Concentration of CO_2 in Earth's atmosphere is important because CO_2 can trap heat in this process. Earth's atmosphere is transparent to sunlight, and when the ground absorbs the sunlight, it grows warmer and radiates at infrared wavelengths. However, CO_2 makes the atmosphere less transparent to infrared radiation, so infrared radiation from the warm surface is absorbed by the atmosphere and cannot escape back into space. That traps heat and makes Earth warmer.
EARTH - Global warming
The increased concentration of CO_2 (thought to be caused by humans burning fossil fuels) is increasing the greenhouse effect and warming Earth.
EARTH - Albedo
Fraction of the sunlight hitting it that gets reflected away. Planet with albedo of 1 would be white, albedo of 0 would be black. Earth is .39 meaning reflects into space 39% of sunlight that hits it.