Transcript Powerpoint

EART 160: Planetary Science
NASA/JPL/Malin Space Science Systems
Last Time
• Planetary Surfaces
– Tectonics
– Stress and Strain
– Faults and Folds
Homework
• Keep your units! Make sure things come out
dimensionally.
• Watch those negative signs! Potential Energy is
NEGATIVE.
Wrong Way
Right Way
Eth  U i  U f
Eth  U i  U f
 3 GM   3 GM
   
Eth   
 5 2R   5 R
3
1
2 1
Eth   GM 
 
5
 2R R 
3
 1 
Eth   GM 2 

5
 2R  R 
2
2



3

2 1  1
Eth   GM    1 
5
 R  2 
3
1
2 1
Eth   GM    
5
2
R
3
2 1 
Eth   GM  
5
R
Emits negative
energy?
 3 GM 2   3 GM 2 
   

Eth   
 5 2R   5 R 
3
 1 1
Eth   GM 2 
 
5
 2R R 
Not Equivalent
Expressions
3
2 1 
Eth  GM 

5
 2R 
Factor of 2 here
Today
• Paper Discussion
– Mars Crust and Mantle (Zuber et al., 2001)
– Io Volcanism (Spencer et al., 2007)
• Planetary Surfaces: Gradation
–
–
–
–
–
Fluvial (Water)
Aeolian (Wind)
Glacial (Ice)
Mass Wasting (Gravity)
Sputtering (Charged Particles)
• Planetary Surfaces: Tectonics
– Elastic Flexure
Gradation
• Erosion, Transport, and Deposition of surface
materials.
– Rapid compared to other geologic processes
• Erosion – Displacement of solid material by ice,
wind, or water
– Weathering – chemical breakdown of minerals in the
rocks, often concurrent w/ erosion, but distinct
• Mass Wasting – Downslope movement of
material due to gravity
• Sputtering – Alteration of the surface due to
charged particles (solar wind)
Erosion and Deposition
• Require the presence of a fluid (gas or
liquid) to pick up, transport and deposit
surface material
• Liquid transport more efficient
• Important process on Earth, Mars, Titan,
Venus
• Aeolian: Wind
• Fluvial: Flowing Water
• Lacustrine: Lakes
• Glacial: Ice
Aeolian Features (Mars)
• Wind is an important process on Mars at the present
day (e.g. Viking seismometers . . .)
• Dust re-deposited over a very wide area (so the
surface of Mars appears to have a very homogenous
composition)
• Occasionally get global
dust-storms (hazardous
Martian dune features
for spacecraft)
• Rates of deposition/
erosion almost unknown
30km
Dust Devils
Image of a dust devil
caught in the act
Aeolian features (elsewhere)
Namib desert, Earth
few km spacing
Longitudinal dunes, Earth (top),
Titan (bottom), ~ 1 km spacing
Yardangs (elongated dunes)
Mead crater, Venus
Wind directions
Venus
Mars (crater diameter 90m)
Wind streaks, Venus
Global patterns of wind
direction can be compared
with general circulation
models (GCM’s)
Fluvial features
• Valley networks on Mars
• Only occur on ancient
terrain (~4 Gyr old)
• What does this imply
about ancient Martian
atmosphere?
100 km
30 km
• Valley network on Titan
• Presumably formed by
methane runoff
• What does this imply
about Titan climate and
surface?
Martian Outflow channels
• Large-scale fluvial features,
indicating massive (liquid)
flows, comparable to ocean
currents on Earth
• Morphology similar to giant
post-glacial floods on Earth
• Spread throughout Martian
history, but concentrated in the
first 1-2 Gyr of Martian history
• Source of water unknown –
possibly ice melted by volcanic
eruptions (jokulhaups)?
flow
direction
50km
150km
Baker (2001)
Martian Gullies
• A very unexpected discovery
(Malin & Edgett, Science 283,
2330-2335, 2000)
• Found predominantly at high
latitudes (>30o), on polefacing slopes, and shallow
(~100m below surface)
• Inferred to be young – cover
young features like dunes
and polygons
• How do we explain them?
Liquid water is not stable at
the surface!
• Maybe even active at
present day?
Lakes
Clearwater Lakes Canada
~30km diameters
Titan, 30km across
Titan lakes are (presumably)
methane/ethane
“The Rain on Titan(e) falls mainly as ethane” – Larry Esposito
Glaciation
Perito Moreno Glacier, Patagonia, Argentina
Image Credit: Luca Galuzzi - www.galuzzi.it
Glaciation not terribly common on planets
Icy satellites so cold, ice behaves as rock
Mars Polar Cap
Image Credit NASA
Erosion
• Erosion will remove small, near-surface craters
• But it may also expose (exhume) craters that were
previously buried
• Recently recognized as a major process on Mars, but
the details are still extremely poorly understood
• Below: Examples of fluvial features which have been
exhumed: the channels are highstanding. Why?
channel
meander
Malin and Edgett, Science 2003
Sediments in outcrop
Opportunity (Meridiani)
Cross-bedding indicative of prolonged fluid flows
Mass Wasting
• Movement of soil, regolith, rock downslope due
to gravity
• Occurs when gravity exceeds resisting force 
slope failure
• Downhill creep (slow, minute fluctuations)
• Landslides
• Flows (e.g. mudslides, avalanches)
• Rock falls
• Can be triggered by earthquakes, undercutting
by erosion, freeze-thaw.
• Does not require an atmosphere
Euler Crater on the Moon (Source: NASA)
Terraced crater walls due to slope failure
Ganges Chasma on Mars (Source: NASA)
Devil’s Slide, HWY 1, SF Chronicle
Anim. GIF – U. of Sannio, Italy
Types of Mass Wasting
NASA
Sputtering
• Bombardment of a material by charged
particles (ions) resulting in atoms ejected
from surface.
• Important on Asteroids and the Moon
• Why doe the Moon have no atmosphere?
• Much of Mars’ atmosphere sputtered
away.
Tectonics on Icy Moons
Iapetus has
A great ridge ‘round the middle
What is up with that?
Miranda – Broken apart
and put back together.
Iapetus said to Miranda
“You’re really no place for a lander.
Your canyons have rocks
Like the teeth on some crocs,
Whereas I’m black and white like a panda.”
Coronae on Venus
Planetary stretch mark.
Plume pushing up from below.
Gives YOU stretch marks!
Gut pushing out
Yet Another Talk!
Ross Beyer
NASA Ames Research Center
HiRISE views of Martian
Strata and Slope Streaks
Today, 3:30 pm
Earth and Marine Sciences (E&MS) Building, Room B210
Tea and snacks in the E&MS Atrium at 3:00PM
Next Time
• Done with Surfaces?
– Elastic Flexure?
• Planetary Interiors
– Heat Sources
– Cooling Mechanisms
– Geodynamics
– Seismology
– Magnetism
• Homework 3 due Monday