GEO303C Lectures 1-27
Venus: Mass Distance from the sun Rotation Spin Surface temp Covered in.. Atmosphere Surface pressure
0.95 Earth mass (nearly the same size) 0.72 AU Slowest rotation of any planet - 243 days Spins backwards! 337-487 C/710-908 F (hotter than Mercury) Clouds! Thick and dry mostly CO2 100 times higher than Earth's
What are the basic stages of Solar System formation?
1) Collapse of giant gas/dust cloud 2) Formation of rotating disk 3) Condensation of solids and formation of planetesimals 4) Accretion of planetesimals to form embryos 5) Runaway growth
How can we learn about the formation of our solar system?
1) Planetary science - sizes, orbits, compositions and physical properties of our planets 2) Meteorites - provide samples of the oldest objects in the Solar System 3) Astronomy - we can learn about how starts form by looking at ongoing star formation elsewhere in our galaxy
What is the data that we have to explain the formation of the Solar System?
1) Planets isolated 2) Orbits circular/in the same plane 3) Planets and most moons travel along orbits in the same direction same direction as Sun rotates - counterclockwise 4) Not all planets rotate this way though 5) Solar System highly differentiated - Terrestrial planets are rocky and denser/Jovial planets are gassy (H&He) with lower densities
Uranus Composition Atmosphere/Why is it blue? Moons/Rings Surface temp Rotation/Orbit
15% H, little He mostly ices - uniform throughout no rocky core Blue from methane absorption of red light and has mostly hydrogen and helium 27 moons, 11 rings -212 C at surface 18hr rotation, 84 year orbit
Earth's moon: Radius Mass Density
1738km radius ~1% the mass of the Earth Lower density = 3.3 g/cm^3 vs 5.4 g/cm^3
Mercury: Radius Mass Average distance from the sun Density Cratered?
2440km radius ~6% the mass of Earth 57.9 million km - 0.39 AU 5.43 g/cm^3 Heavily cratered
Jupiter: Mass Larger than Density How many moons?
318x the mass of Earth Larger than all the other planets combined 1.33 g/cm^3 gas giant Over 39 known satellites
When did the solar system form? How do we know?
4.56 billion years ago Evidence for formation Lunar samples - up to ~4.5 Ga (Ga=giga anna = billion years) Meteorites - 4.56Ga Earth - oldest rocks 3.9 or 4.4 Ga
What is the sun's surface temperature? Core temperature?
5770K - surface 15 million K - core
Earth: Diameter Axis tilt Surface temp Atmosphere
7900 mile diameter (12756 km) 23 degree axis tilt = seasons -73 to 48 C/-100 to 120 F Thick atmosphere with a mild greenhouse effect
What is Jupiter's rotation speed?
9.9 hours = 1 day on Jupiter This is ridiculously fast
The sun is made up of what? How much (percentage wise) of each element?
92% H and 8% He
Saturn: Mass Density Atmosphere
95x the mass of the Earth Very low density (0.69 g/cm^3) <-- would float in water Massive atmosphere of H, He, and methane (like Jupiter)
The sun is _____% mass of the Solar System
99.85
<,>,=? Dust particles __ softball sized objects Softball sized objects ___ 1km planetesimals Planetesimals ___ proto-planets
=> => => collided with other planetesimals and formed
What did the Magellan spacecraft reveal about Venus' surface?
A diverse landscape with jagged mountains, abundant volcanic features yet very few craters
What does Venus' dense atmosphere produce and what does this prevent?
A run-away "greenhouse effect" which obscures the planet's surface from view. HOWEVER - the Magellan space craft revealed Venus' startling and complex surface using radar which penetrates the atmosphere
What is AU?
AU - Astronomical Unit 1AU = Earth's distance from the sun
Where can we see zonation?
Around other proto-stars
What happens as the cloud collapses in the Solar System formation process?
As the cloud collapses and spins faster it flattens into a disk with a protostar in the center
What is the atmosphere of Io like? Why is it like that?
Because of Io's volcanism, Io has a tenuous atmosphere composed primarily of sulfur dioxide.
What are Jupiter's 4 largest known satellites? What are they sometimes referred to as? Which is the biggest?
Calisto, Ganymede, Europa and Io They are sometimes referred to as Galilean satellites Ganymede is the biggest
What are Venus' clouds made up of?
Clouds of sulfuric acid and a crushing C02 atmosphere obscure a surface temperature which is hot enough to melt lead.
What do gravitational interactions between a large number of initial planetesimals lead to?
Collisions and growth of planetesimals
What is the rapid rotation combined with? What does this help produce?
Combined with convection driven by heat from the interior which helps produce the stark atmospheric banding severe and long-lived storms and unimaginable winds.
Neptune: Composition Atmosphere Rings/Moons Rotation/Orbit
Comp: Ices and rock - 15% H and little He - uniform throughout possible small rocky core Atmo:H, He and methane atmosphere = blue 4 rings/13 moons 18hr rotation/165 year orbit
What is the asteroid belt composed of?
Composed of thousands of bodies ranging from less than a km in size up to nearly 1000km
Different compounds ___________ at different temperatures. Silicates are...?
Condense; rock forming minerals
What are the 2 models of formation for the Jovial planets?
Core accretion Gravitational instability
What are Saturn's rings composed of?
Countless small icy particles ranging in size from ~1m - <1 micrometer
What might be the home to earliest life forms on Earth and how does this relate to Jupiter's moon Europa?
Deep-sea hydrothermal vents may have been home to the earliest life forms. This is related to Europa because similar vents beneath Europa's icy crust could provide a habitat for life
Europa: Density Composition Surface
Denser than Ganymede and Calisto (2.99 g/cm^3) Made primarily of rock Surface is icy which is only lightly cratered and lightly covered with a very complex network of cracks, ridges and grooves
What are many young stars surrounded by? Does this include our sun?
Disks of dust and gas, just as our sun was 4.5 billion years ago
Pluto: Diameter Rotation/Orbit Surface
Dm: 1,413 miles - 2/3 size of Earth's moon (lower mass) R: 6 1/3 days; 248 year elliptical Surface of water and methane ice and frozen nitrogen
What do dust bunnies have to do with the birth of our Solar System?
Dust bunnies are small clumps of dust that are held together by static electrify and felt like entanglement
There is a lot of ______ tied up in chemical bonds. What is this a result of?
Energy. This is what happens when you combine hydrogen and oxygen
What is on the surface of Io that can extend hundreds of km into space?
Eruption of Pele volcano
How long did the formation of the solar system take?
Evidence for the initial presence of now extinct short-lived radioactive isotopes in the early solar system suggest the whole process from start to finish took <50 Ma for the terrestrial planets
Mars has evidence of what 2 things in it's past?
Extensive volcanism and water
What happens in Step 2 of the Nebular Hypothesis?
Flat rapidly rotating disk with a proto-sun The cloud spins more rapidly as it collapses because of conservation of angular momentum
What is step 3 in the Nebular Hypothesis?
Gas and dust collide to form planetesimals The enveloping disk of gas and dust forms grains that collide and clump together into small chunks of planetesimals
How did we get a solar system?
Gravitational accretion: planetesimals attract stuff Large protoplanets dominate, grow rapidly and clean up the area
Mars: Mass Distance
His favorite planet not counting Earth 11% of Earth's mass 1.5 AU = ~50% as much solar energy
What landed on the surface of Titan in Jan. 2005? What did we learn about the world of Titan from this? What are the materials similar to?
Huygens probe; Images that were sent during the descent revealed a world of methane rain and hydrocarbon rivers and lakes of pre-biotic organic soup; These ingredients were probably instrumental in the origin of life on Earth
What is Jupiter's atmosphere primarily composed of?
Hydrogen and Helium (although methane and other gases are also present)
Triton Surface Atmosphere
Ice volcanos - geysers and ridges and valleys The atmosphere is thin made of nitrogen and methane
Why is Venus compared to Earth?
It can be considered our evil twin because it is so similar in size, composition and distance from the Sun
What is special about Enceladus' surface? What does this tell us about the surface? What else can be found on the surface of Enceladus?
It has Tiger Stripes which are cracked features about 130km long and 40km apart that run roughly parallel to each other that tell us that the icy moon is between 10-1000 years young You can also find geysers of water jet from the surface of Enceladus
What happens on Jupiter's equator?
It is really windy. The winds can reach velocities of up to 150 m/s
What is condensation?
It is the process by which solid grains formed as the initially hot solar nebula began to cool (like snow flakes forming in a cloud)
Why is Venus' rotation special?
It rotates backwards!
What is special about Uranus' axis?
It spins on an axis that is inclined almost 90 degrees
How was the proto-planetary disk heated?
It was heated by accretion of material falling onto the disk (release of gravitational energy), by friction and by the growing proto-sun
Europa's proximity to ______ and ______ _________ with other Galliean satellites results in _______ __________. What does this do to Eurpoa's interior?
Jupiter; gravitational interaction; tidal heating Warms Europa's interior
What does runaway growth lead to?
Leads to the formation of a small number of large objects from the initial large population of planetesimals
What is unique to Earth's surface?
Liquid water and lots of it!
The lunar crust can be divided into the dark colored lowlands (______) and light colored ________ ____________ highlands.
Mare; heavily cratered
How did we get a Solar System? Where were the lower temperatures and what was involved?
Metallic elements(Mg, Si, Fe) condensed into solids at high temps and combined with Oxygen to make tiny grains Lower temperatures (H, He, CH4, H20, N2 ices) were at the outer edges
How old is the sun?
Middle aged = 4.5 billion years old and will probably keep going another 5 billion or so
Calisto: Composition Surface Active/Inactive
Mixture of rock and ice Heavily cratered Inactive for a long time
What are Saturn's moons like?
Most of it's satellites are icy worlds composed of water, CO2 and methane ice
Why is the Earth less heavily cratered than the moon?
Most of the records of bombardment of Earth has been erased by processes of tectonics, weathering, erosion and sedimentation.
Is Jupiter just a failed star? What is the minimum mass for nuclear fusion?
NOT A FAILED STAR Min. mass ~75x that of Jupiter
What do the few impact craters on Venus' surface tell us?
No craters less than 3km (meteoroid ~ 30m across) Atmospheric filter The surface is active and the volcanic activity is causing resurfacing
What is Pluto considered now? When did it lose its status?
Now a dwarf planet; 2006
What is the sun powered by?
Nuclear fusion in the core
What do observations from astronomy reveal about where stars are formed? What is the place of formation like?
Observations from astronomy reveal that stars are formed primarily from giant "Molecular Clouds" This place is cold, dense (by the standards to space) and clouds of dust and gas concentrate in the spiral arms of our Galaxy.
How big is the sun in diameter? The sun is how many km from us?
Over 1 million km in diameter 150 million km away from us
How do we know that the proto-planetary disk was initially hot?
Refractory phases called CAIs (Calcium-Aluminum Inclusions) formed by condensing from hot gas. Aside from being especially close to the sun round chondrules formed by flash heating/melting of dust accumulations, probably because of the shock waves in the disk
What are the cores of the outer planets like? How big are they? What are their atmospheres like?
Rocky cores several Earth masses in size Dense atmospheres of H2 and He similar to sun, but enriched in heavier gases relative to solar composition.
Ganymede: Composition Surface Active/Inactive
Similar to Calisto (mixture of rock and ice) Heavily cratered in some areas and in others not so much. Also there are massive fractures and grooves cut across the planet. More past active than Calisto because of all the fractures and grooves
The sun is the source of what?
Solar wind and space weather
What is special about Pluto's orbit?
Sometimes it is inside Neptune's orbit and when it gets closer to the Sun the heat produces an atmosphere
Io: Tidal heating Active/Inactive Density Composition Surface
TIDAL HEATING HAS GONE MAD Most volcanically active body in the SS High density (3.53 g/cm^3) Rocky composition No impact craters because the surface is constantly being reworked by volcanism
What is step 4 in the Nebular Hypothesis?
Terrestrial planets form from planetesimals The terrestrial planets build up by multiple collisions and accretion of planetesimals by gravitational attraction. Giant outer planets grew by gas accretion
What is going on in the spots of Neptune?
The Great Dark Spot had a storm and there is a Pretty Good White Spot (Scooter) which zips around every 16 hours
Venus and Mars are two extremes of what?
The Greenhouse Effect
What lies between the orbits of Mars and Jupiter?
The asteroid belt
Where do most meteorites derive from?
The asteroid belt
What might Europa's crust be hiding?
The icy crust might be quite thick which would be hiding an ocean of liquid water several hundred km thick
Is Enceladus still active?
The moon's southern pole is still active with geological activity as recent as 10 years ago.
How did Saturn's rings get like that?
The rings may be the result of the catastrophic breakup of a satellite due to impact
Why do Saturn's rings have gaps and grooves?
These are a result of the gravitational interactions with "shepherd" satellites
What do Enceladus' tiger stripes do? How does the crystallization process come into play?
They act like vents and spew vapor and fine ice water particles this crystallization process is what helps us pin down the age of the features
Comets are made of what?
They are dirty snowballs - small objects of ice, gas, dust, tiny traces of organic material
How do the largest objects grow in the formation of the solar system?
They grow fastest and clear their orbits by canibalizing other planetesimals in their region of space
What do planetary compositions reflect?
They reflect this temperature driven compositional zonation.
What do numerical models from astronomical observations and findings in meteorites show?
They show that peak temperatures in the inner solar system would have been hot enough to evaporate all solids
How does this disk form?
This disk forms due to the accelerated spinning of the gas/dust cloud that results from contraction
What is the name of Saturn's largest moon? Why is it said that it's appearance is deceiving?
Titan; It's bland featureless appearance is the result of a thick hazy nitrogen atmosphere that also contains methane and hydrocarbons
What happens in the first step of the Nebular Hypothesis? What are the forces involved? What happens if gravity wins?
We start with a large cloud of ~99% gas (mostly H2 and He) and dust. Forces acting to collapse the cloud: Gravity Forces acting to prevent collapse: Gas pressure; turbulence; magnetic fields. If gravity wins, we've started the process of star formation.
Is the moon impacted often?
YES. It has been bombarded frequently and still continues to get bombarded 500 million years after the formation of the solar system
Is the Earth geologically active? What are the layers of the Earth?
Yes. Solid inner core, liquid outer core, mantle, crust then magnetic field
Chemical energy is nothing compared to...?
energy released from nuclear fusion
Metals condense at...? Ices condensed in...?
high temperatures; the colder outer portions of the disk, but not inward of the "snow line"
The pressure and temperature in the sun's core is so high that...
hydrogen atoms fuse together to form helium
Earth undergoes ______ has a _______ core. Earth is the perfect place for ______ to evolve.
plate tectonics; liquid metal; life
Young _______ _________ complex terranes suggest that Europa's surface has been reworked by ___________.
sparsely cratered; cryovolcansim
Mars used to be ____ and _____ during the 1st billion years but today it is _____ and ______.
warm; wet; cold; dry
