EART 160: Planetary Science NASA/JPL/Malin Space Science Systems

Planetary Surfaces –Tectonics –Stress and Strain –Faults and Folds Last Time

Homework Keep your units! Make sure things come out dimensionally. Watch those negative signs! Potential Energy is NEGATIVE.

Wrong Way Right Way Not Equivalent Expressions Emits negative energy? 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 for spacecraft) Rates of deposition/ erosion almost unknown 30km Martian dune features

Dust Devils Image of a dust devil caught in the act

Aeolian features (elsewhere) Namib desert, Earth few km spacing Yardangs (elongated dunes) Mead crater, Venus Longitudinal dunes, Earth (top), Titan (bottom), ~ 1 km spacing

Wind directions Venus Wind streaks, Venus Global patterns of wind direction can be compared with general circulation models (GCM’s) Mars (crater diameter 90m)

Fluvial features Valley networks on Mars Only occur on ancient terrain (~4 Gyr old) What does this imply about ancient Martian atmosphere? 30 km Valley network on Titan Presumably formed by methane runoff What does this imply about Titan climate and surface? 100 km

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)? Martian Outflow channels 50km flow direction 150km Baker (2001)

Martian Gullies A very unexpected discovery (Malin & Edgett, Science 283, , 2000) Found predominantly at high latitudes (>30 o ), on pole- facing 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 Titan, 30km across Clearwater Lakes Canada ~30km diameters 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 - Mars Polar Cap Image Credit NASA Glaciation not terribly common on planets Icy satellites so cold, ice behaves as rock

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? Malin and Edgett, Science 2003 meander channel

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