Descriptive Astronomy 101
Planetary Geology


Planetary Geology

Planet means _______________
Study of planets is still in the field of Astronomy
Recent probe and exploration have moved planetary studies into the realm of Geology

Exploration

Telescopic Observations
Human Exploration - Apollo 11, 12, 14, 15, 16, 17
Planetary Probes (excluding Earth orbiting)
Mercury: Mariner, Messenger
Lunar: Pioneer, Luna, Ranger, Surveyor, Lunar Orbiter, PFS, Hiten, Hagoromo, Clementine, Lunar Prospector
Mars: Mars, Zond, Mariner, Cosmos, Viking, Phobos, Mars Observer, Mars Global Surveyor, Mars Pathfinder, Nozomi, Mars Climate Orbiter, Mars Polar Lander, Mars Odyssey, Mars Express, Spirit, Opportunity
Asteroids: NEAR, Hayabusa, Deep Space 1
Outer Planets: Pioneer, Voyager, Galileo, Cassini
Comets: Giotto, Stardust, CONTOUR, Rosetta

Additional information can be found at the Planetary Geology - Exploration page.

Interior Structure

Differentiated interior: density layering

Core
Terrestrial:
Jovian:

Mantle
Terrestrial:
Jovian:

Crust
Terrestrial:
Jovian:

Atmosphere / Ocean
Terrestrial:
Jovian:

Tectonic Activity

Deformation and structural behavior of crustal material.
Heat from the core drives convection in the mantle.
Sources of Heat?
Mantle convection creates stress in the crust causing it to deform
Tectonic activity only occurs in planets with warm interiors.
Why?

Tectonic Stress

Stress is any force which acts to deform rocks.
Compression -
Tension -
Shear -

Volcanism

Heat from the core migrates towards the crust and causes mantle and crustal material to melt.
Molten or melted material is called ___________.

Volcanism

Magma is hot, therefore less dense than the surrounding material
What happens to the magma?
1)
2)
If the magma rises through the crust and reaches the surface:
1)
2)

Types of Volcanic Rock

There are 3 main types of volcanic rock
Basalt: mafic composition, dark color - rich in Fe, Mg and Ca, poor in silica (SiO4)
Andesite: intermediate composition, medium color - moderate amounts of Fe, Mg, Ca, Al, K, Na, and silica
Rhyolite: felsic composition, light color - rich in silica, Al, K and Na, poor in Fe, Mg and Ca

Types of Lava Flows

Pahoehoe - very fluid flows - low viscosity; ropy surface appearance; basalt
Aa - higher viscosity than pahoehoe; surface consists of spiny, angular clinkers; basalt, andesite
Pillow Lava - basalt lava flows; form when eruption or flow occurs underwater
Block flows - surface consists of angular blocks; andesite, rhyolite, obsidian

Impact Craters

Impact crater:
Small craters (simple craters) are <16 km diameter; smooth bowl- or cone-shaped interiors (some with flat bottoms) - exterior deposits slope away from rim
Large craters (complex craters and basins) - roughly circular, terraced rims with a central peak or ring peak, surrounded by hummocky debris; >16 km diameter

Impact Basins

The term applied to craters larger than 200 km is basin
Similar structure to large craters, but bigger
- roughly circular
- terraced rims with a central peak or ring peak
- surrounded by hummocky debris
- multi-ringed
- lava flows often fill the basin bottom

Cratering Process - Simple Craters

1)
2)
3)
4)
5)
6)

Cratering Process - Large Craters and Basins

1)
2)
3)
4)
5)
6)

Erosion

The mechanical and chemical destruction of the land (weathering) and the removal or transportation of material by flowing liquid (water), flowing or moving solids (ice, glaciers, impactors) or moving gas (wind).

Space Weathering

The alteration of the surface of small bodies unprotected by an atmosphere.
Iron nanoparticles are formed by the evaporation of minerals during micrometeorite impacts or exposure of the surface to the solar wind
Iron nanoparticles then condense onto nearby mineral surfaces
Importance of this process: