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Phys 1810 Lecture 13:
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Planets, asteroids, comets: Use material in lecture as a
guide for topics to read about in text book on each planet.
READ BEFORE LECTURE:
– Solar System Chapt 6
– Greenhouse effect P. 166-167, P. 231
– Mars e.g. Box “More Precisesly 8-1”
– formation of the moon 8.8
– exoplanets Chapt 15
Topics include
– scale, objects
– terrestrial vs jovian
– planetary system formation including (differentiation)
– Mars
– Earth – climate change
– planetary system formation including differentiation
Jupiter’s Aurora
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• surrounding core is metallic H  B
field  aurora
• composition of core “rocky”
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the deep atmospheres of the gas giants may contain chunks of
diamond floating in liquid hydrogen/helium fluid.
carbon such as soot or graphite generated in Saturn's enormous
lightning storms will descend and be crushed into diamonds at deep
altitudes and then melted into liquid diamond near the cores of the
planets.
diamonds may be floating around inside of Saturn, some growing so
large that they could perhaps be called "diamondbergs."
Jupiter’s rings in IR
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Tour of the Solar System: Uranus
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Keck Observatory IR
Weather
• Rings
Tour of the Solar System: Neptune
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Visible +IR
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Voyager2/NASA
• Rings.
• Seasons due to inclination of
rotation axis to orbital plane.
summary
Saturn
Cassini/NASA
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Tour of the Solar System: Saturn
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Cassini-Huygens/NASA/ESA
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• How did the rings form? Three possibilities.
1. Similar to a planetary disk formation but on a
smaller scale. (We’ll do planetary disk formation shortly.)
2. Tidal forces causing orbiting low density moons
to fragment.
Saturn’s Moon Enceladus
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3) Spewing ice plumes through (“blue”)
tiger stripes
 E ring
Tour of the Solar System: Saturn
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Spitzer/NASA
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• Large Infra-red ring! (Moon Phoebe orbiting
within this ring.)
• diameter equivalent to 300 Saturns.
• ~ 20 Saturns for its vertical height.
• Too large for field of view of HST and too faint
in visual range for optical telescopes.
Saturn’s Moon Enceladus
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Other moon’s with
atmospheres:
- Enceladus
- Triton
- Io
- Titan
- Dione
• has an atmosphere
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News!
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Tour of Solar System: Saturn’s Moon Titan.
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Cassini-Huygens/NASA/ESA
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UV in false color
• Atmosphere: Note upper layer of haze.
• Thick enough to have polar vortex.
• Seasonal changes due to tilt of spin axes.
Titan Vortex is toxic
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• Spectral map
• signature of frozen hydrogen cyanide molecules
(HCN).
• T atmosphere needs to be 125K (-148C)
• suggests atmosphere of Titan's southern
hemisphere (currently Autumn) is cooling much
faster than expected.
Tour of Solar System: Saturn’s Moon Titan.
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Cassini-Huygens/NASA/ESA
Visible
+ IR
Ontario Lacus at
South Pole
• Ethane lake. Ethane created by
sunlight breaking apart methane.
• Only other solar system object
known to have liquid on the surface.
Titan: “come and go” feature in lake.
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• dark areas represent the sea, composed of
mostly methane & ethane (hydrocarbon).
• bright areas represent land surface above or
just beneath water line.
• feature in bottom middle of image could be
surface waves, rising bubbles, floating solids,
solids that are suspended just below surface
or perhaps something more exotic.
summary
Moon of Neptune: Triton
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Voyager 1989 data processed in 2014
• Triton has an atmosphere.
• possibly a Pluto-like object that Neptune
pulled into orbit.
Why study Mars instead of Venus?
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• Mars more likely to tell us how life
originated in solar system
• Venus too hostile due to its
greenhouse effect.
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Greenhouse on Earth
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• Intergovernmental Panel on Climate
Change. IPCC won Nobel Prize.
• 1000s of scientists volunteer to IPCC.
• Solar luminosity contribution to global
warming (blue line above) is small.
• increase in greenhouse gases (since
industrial revolution ~ 1750)
• See IPCC summary & FAQ on web.
Greenhouse on Earth
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• Details about these plots:
Note: these are not
• black line == measured data  T is rising. predicted values.
• Computer simulations use laws of physics &
assumptions. Uncertainties width.
• Blue: Modelling just natural forces (includes variation in
sun’s luminosity) – stable T.
• Pink: Modelling both natural forces & impact of human
beings – match observed T better.
New IPCC report – trends continue
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Greenhouse on Earth
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• These are measurements over time
of amount of each green house gas.
• Notice the “spike” is much higher in
value than the uncertainties in the
measurement.  spike is not an
error.
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Sun’s Influence: On Earth
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Summary: The sun has influence
throughout the solar system &
our distance from it allows liquid
water. However the solar cycle &
activity is not responsible for
global warming. Human activity is
a likely cause.
• Check the King’s Centre for
Visualization in Science for
interactives on climate change:
http://www.kcvs.ca/site/projec
ts/climate.html
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Greenhouse Effect
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• Most light from sun is near-IR +
visible.
• IR trapped by greenhouse gases +
H2O clouds.
• recirculated for decades.
Venus has CO2 in atmosphere
(volcanic outgassing) + too hot for
oceans
-- CO2 not converted to rocks
runaway Greenhouse Effect.
 inhospitable to life
 Mars of interest for life, colonization, etc.
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Mars
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• NASA/Viking
Tour of the Solar System: Mars
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Mars Global Surveyor Mars Orbiter Camera
NASA/JPL/Malin
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Radius ~ ½ of Earth’s; Mass ~ 1/10 of Earth’s.
Water ice crystals over volcanoes
Pole has water ice and CO2 ice.
Red soil due to iron.
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• ESA/Mars Express
Cydonia Region
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summary
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• NASA’s Spirit
and
Opportunity
rovers.
Tour of the Solar System: Mars
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Spirit Rover/NASA
• Typical surface temperature is -55C
to -63C
• Winnipeggers would survive!
• Sometimes up to +20C.
summary
Olympus Mons
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• Evidence Mars cooled rapidly.
– Different tectonic activity
– B fld 1/800 Earth’s
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Viking Observations
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• Misinterpreted as a sculpted face.
Stereo Camera on Mars Express
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• Movement of the crust raised this
feature, called a massif.
summary
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Example of Wind Action in Crater.
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Escape Velocity of molecules in atm.
More Precisely Box 8-1
Depletion of Upper Atmosphere
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• Charged particles from sun (solar wind)
ionize molecules.
• splits O from H (H escape)
• solar wind drags ions away
• Maven – new mission
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• Depletion by:
– UV photon heating  escape velocity to
atoms
– UV photon ionizing  charged particles
– Solar wind ionizing  charged particles
– ions dragged away by solar wind
• A factor that does not play a role in depletion
of the Martian atmosphere is outgassing from
volcanoes.
Martian Atmosphere.
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• Given the atmospheric pressure can
liquid water currently exist on the
surface of Mars?
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• Water Ice in a crater.
Mars and Water
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Mars Global Surveyor Mars Orbiter Camera
NASA/JPL/Malin
• Water ice crystals over volcanoes
• Pole has water ice and CO2 ice.
summary
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Vallis Marineris
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• Vapour
Current Phases of Water on Mars.
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• Clouds
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Tour of the Solar System: Mars
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Viking/NASA
• Atmosphere is 1/150 of Earth’s (~ 1%)
• 95% CO2
• Pressure < 60% ice sublimates into gas
summary
Tour of the Solar System: Mars
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Viking/NASA
• Vapour and clouds – settle in valleys and channels.
• Currently no detection of liquid water, though rivers
may have flowed in the past when the atmosphere
was denser.
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Outflow Channels
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• Abundances  95% CO2 on Mars.
• Using current abundances & working
backwards in time & using escape
velocity  denser atmosphere in past.
• Also probably similar to composition
of Earth’s early atmosphere.
Look for evidence of liquid water in the past.
Curiosity Rover --- 7 Minutes of Terror
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