Transcript The Solar System

The Solar System
•Inner planets; geology, atmosphere
evolution
•The asteroids – scrambled and fried
•Outer planets and their mini-solar systems
of moons
•Comets: icy dirtballs or dirty iceballs?
Inner vs. Outer Planets
characteristics
Temp vs distance in solar system
All planets and the sun, sizes
How Does a Planet Retain an
Atmosphere?
• Surface gravity must be high enough and
surface temperature must be low enough
that the atmosphere molecules don’t leak
away during the 4.6 billion years since
formation.
Two Ways a Planet Loses
Atmosphere: First…
• Lighter molecules move faster, because on
average Kinetic Energy = Thermal Energy
• (½)m<v>2 = (3/2)kT
• Molecules are continually bouncing off of each
other and changing their speed, but if the average
speed is higher, a few may be speedy enough to
escape the planet’s gravity
• Hydrogen and Helium = 97% of the mass of the
solar nebula, and these are the lightest and easiest
molecules to lose
The Second way to Lose
Atmosphere…
• …maybe easier to understand - Impact Cratering!
Big comets and asteroids hitting the planet will
deposit a lot of kinetic energy which becomes
heat, blowing off a significant amount of
atmosphere all at once.
• This is a Big issue especially in dense areas (inner
solar system), and dense times (soon after
formation).
The Inner Planets
• It’s hot close to the sun. No ices. So only
the rocky material (~3% of the solar nebula)
could collect. Not hydrogen and helium
since escape velocities that are too low for
these
• Atmosphere histories for each planet are
unique…as we’ll see
Early inner planet; a ball of lava
Inner planet interiors; summary
Mercury mariner
Mercury mud cracks
Mercury fault
Mercury
• Smallest planet, only 3,000 mi across.
• 600F on daylight side, too hot to retain any
atmospheric molecules at all. Probably
doesn’t help that the sun is so close and
solar storms can rack the planet and help
carry off any atmosphere too.
• Cratering shows it hasn’t had atmosphere
for most of solar system’s history
venusHST
Venus-all
Venus lava flows
Venus-surface1
Venus-surface2
Venus-surface4
Venera-left
Venera-right
Venus
• Has thick CO2 atmosphere, 100 times
denser than earth’s. CO2 is the heaviest
common molecule.
• Greenhouse effect – CO2 transparent to
visible light coming down from the sun, but
opaque to infrared coming back off the
surface, hence heat comes in but can’t easily
escape. 900K on surface!!
• Let me draw you a picture…
Greenhouse effect
Earth – largest inner planet
• Crust divided into tectonic plates which move due
to friction against the moving molten mantle
underneath. Continental drift animation
• . Click here for animation website.
• This likely explains why the earth
has so little atmosphere. That’s one
heck of an impact event.
Atmosphere; initially rich in CO2,
methane, no oxygen
Why so little atmosphere, and why is CO2 such a tiny %
(~0.3% today)?
1. Life took out CO2 and produced O2, and organic and
inorganic processes produced CaCO3. Nice! This has been
lowering greenhouse gases at the same time the sun has
been increasing its luminosity – balance!
2. Moon created by Mars-sized planet impacting early Earth.
Evidence: (1) moon crustal age is a little younger than
Earth’s, (2) moon composition = Earth mantel
composition, (3) moon orbits ~in ecliptic, not equator
plane as you would expect if it was formed with the earth.
Folded mountains – earth and
Venus
Aurora, iceland volcano
Mt. Aetna in italy
Ozone hole
moonPlieades
moon
Moon’s surface; maria vs
highlands
Mare humorum,
Clavius 160mi across
Apollo 15 on moon1
Apollo 15 on moon
Graze reduction
marsHS
Mars globe, big craters
Mars globe, w/ v. marinaris
Olympic mons caldera
Mars valle marinaris
Mars continents
Mars solis plenum
Martian sand dunes
Mars gullies
Martian surface; pathfinder
Spirit track
Mars mud cracks
Martian rock; blueberries,
razorback
Mars crater edge - rover
Mars BurnsCliffs
Mars drilling rock
Mars frozen ice floes
Mars heart-shaped crater
phobos
Phobos mars orbiter
diemos
Asteroids – Remnants of
planet(s) roughed up by Jupiter?
• Giant gap from Mars to Jupiter, plenty big
enough to house another planet. But
instead…
• Thousands of bits and pieces of rock
• Resonances and orbit crossings led to
collisions, or maybe never came together in
the first place (tidal stretching)
• Total mass is less than that of Mars
The Outer Plants:
Hydrogen/Helium Giants
• 97% of early solar nebula was hydrogen and
helium, roughly the composition of the
outer planets
• Cold temperatures, high mass allow these
light atoms to be held by gravity for these
4.6 billion years
• Rocky cores surrounded by deep layers of
H, He.
Jupiter,Saturn,Uranus,Neptune
lineup
Jupiter layers
Jupiter redspots
Jupiter storms
Jupiter IR, excess heat
Jupiter + Io
Io globe
Io globe closer in
Io volcano
Io pele
Io volcano closeup
Io surface hi res
Io cutaway
Europa cracks
Europa interior cutaway
Lake Vida Antarctic
Callisto ice spires
Ganymede globe gray
Callisto globe
Callisto cratering
Jupiter small rocky moons
saturnHST
Saturn hst2
Saturn rings
Mimas and rings
Cassini division close up
Saturn dragon storm
Saturn aurorae
Saturn aurorae sequence
Titan haze from side
Titan color
Titan b&w oceans
Titan shorelines
titan
Titan ocean+canyon
Titan impact crater
Titan bouldersColor
phoebe
Enceladus-all
Enceladus surface wedge
Enceladus surface
Enceladus surface2
Enceladus cracks
Mimas
Rhea cassini
iapetusWalnut
saturnMoonEpithemus
Uranus, rings in ir
Uranus,ringsHST
oberon
Miranda lowres
Miranda hi res
Miranda bullseye
Miranda cliff
Neptune HST
Neptune great dark spot
triton
Beyond Neptune – cold and
dark!
• No planets beyond Neptune, instead, the
Kuiper Belt of large comets…
• “rocks” of light elements (hydrogen,
oxygen, nitrogen, carbon, chlorine…) are
called “ice” and melt at very low
temperatures.
• Globs of this stuff, mixed with plenty of
dust and dirt, are called “Comets”!
Hyakutake sahuaro
Hyakutake fisheye
Hyakutake long fl lens
K4 LINEAR
K4 LINEAR; longer exposure
C/NEAR with SOHO
Comets – A Tale of Two Tails
• Comets swing by the sun on big arcing orbits.
• The gas is blown back rapidly, since gas atoms are
very light. Gas tail is very straight and moves very
fast – gas atoms left comet very recently.
• Dust tail is yellowish and often curved, as the dust
grains move very slowly, showing the history of
the comets path over a longer history.
C/Machholz
C/Hale-Bopp
C/Hale-Bopp Jtree
C/Bradfield & LINEAR T7
C/IkeyaZhang and M31
Comet surface - artist
Halley closeup
C/Borrelly closeup
C/Wile closeup/ composite
Comet P57 breaking up
S4 LINEAR breakup b&w
S4 LINEAR breaking up
S4 LINEAR up close
S4 LINEAR4
S4 pieces
SL9 string of comets
Crater chain on moon
Comet TempleTuttle; Leonids
parent
Uniform vs Leonid meteor
streams
Leonids ’99 Ayers antiradiant
Leonids ‘01
Leonids ’01 fisheye
Leonids ’01 fisheye2
Leonids ‘02
Leonids Jtree
Leonids ’02 anti radiant
Leonids ’02 from space
Leonids ‘02, lake moon
DeepImpact
KBO’s
Sedna, quaoar, pluto, earth/moon
Asteroids – Remnants of
planet(s) roughed up by Jupiter?
• Giant gap from Mars to Jupiter, plenty big
enough to house another planet. But
instead…
• Thousands of bits and pieces of rock
• Resonances and orbit crossings led to
collisions, or maybe never came together in
the first place (tidal stretching)
• Total mass is less than that of Mars
asteroidTrails
Inner SS known asteroids all
Pallas occultation
Radar of 3.5km NEO
AnnFrank from Stardust
Eros, whole thing
Eros Landing Site
Eros surface
gaspra
Ida and Dactyl to scale
Asteroid close encounters have changed some
orbits, creating a population of earth-crossing
asteroids. Those that haven’t already hit us,
probably will in the (hopefully distant) future,
Causing….
Trouble!
Daylight fireball
Michelle’s car
Fresh Russian Crater
MeteorCrater, Arizona
Chixilub crater