Quark’s Holiday Tour Part II: the Inner Planets of Sol N. Lindsley-Griffin, 1998 Mars Venus Terra Mercury Jupiter

Composition - All have: metallic core siliceous mantle basaltic crust Relatively dense: g/cm 3 Different history from Jovians All shaped by: 1. Impact cratering 2. Volcanism 3. Tectonism 4. Erosion and deposition Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 Geology of Terrestrial Planets Quark’s Holiday Tour Terra (“Earth”) Venus Mars Luna (“Moon”) Mercury

A planet’s evolution is controlled by how long internal heat lasts Luna (Earth’s Moon) is small, became quiet 3 b.y. ago Terra (“Earth”) is large, stilll hot, remains dynamic today N. Lindsley-Griffin, 1999 Evolution of Terrestrial Planets Quark’s Holiday Tour

Venus - carbon dioxide Earth - nitrogen/oxygen Mars - carbon dioxide Venus - runaway greenhouse effect No plate tectonics Too much Solar energy Earth - plate tectonics recycles oxygen by subducting and remelting oceanic lithosphere and sediments Carbon dioxide trapped biogenically Size and mass just right to maintain internal heat that drives tectonic cycle Mars - water, oxygen locked up in rocks No plate tectonics Too small to hold dense atmosphere Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 Atmospheres - Venus, Earth, Mars Quark’s Holiday Tour

Crater Density and Age of Surface Many craters on older, original lunar crust (anorthosite brecciated by repeated impacts) Fewer craters on younger crust of basalt in the lunar mare (dark colored basins) Crater density provides relative dating for lunar surfaces N. Lindsley-Griffin, 1999 LUNA Quark’s Holiday Tour B A CD b.y. ago Crater Density (arbitrary units)

MARS: Tectonics Quark’s Holiday Tour Huge rift valleys (grabens) cut the northern hemisphere Valles Marineris, largest canyon in the solar system, is 4500 km long, 2-7 km deep, formed by crustal rifting N. Lindsley-Griffin, 1998 Tharsis Bulge, shield volcanoes Valles Marineris, a graben

MARS: Olympus Mons Quark’s Holiday Tour Largest volcano in the solar system Shield Volcano Summit Caldera Larger than the entire Hawaiian islands No linear track (therefore no plate tectonics) N. Lindsley-Griffin, 1998

MARS: Atmosphere Quark’s Holiday Tour Atmosphere is thin, rich in CO 2 Iron in rocks has weathered to red oxides Winds produce ventifacts and dune fields, deposit wind-blown sediments N. Lindsley-Griffin, 1998

MARS: Climate and Ice Caps Quark’s Holiday Tour Strongly elliptical orbit causes huge variation in seasons Average temp. -55°C (-67°F), but ranges from winter low of -133°C (-207°F) to summer high of 27°C (80°F) Ice caps wax and wane with the seasons, causing 25% change in global atmospheric pressure N. Lindsley-Griffin, 1998 Ice caps at both poles are carbon dioxide (“dry ice”) with dust and minor water ice.

MARS: Water Cycle Quark’s Holiday Tour Liquid water cannot exist on surface today No water cycle active today Evidence of water erosion and deposition in the past Major climate change N. Lindsley-Griffin, 1998

MARS: Water Cycle Quark’s Holiday Tour Large floods Small river systems Large lakes or even oceans N. Lindsley-Griffin, 1998 Nirgal Vallis, a runoff channel Fault-bounded canyon Runoff caused by impact?

VENUS: Atmosphere Quark’s Holiday Tour Pressure: 90 atm. Dense clouds of CO 2 and sulfuric acid conceal surface Runaway greenhouse effect traps solar heat at surface Surface temperature 500 o C (melts lead) N. Lindsley-Griffin, 1998

VENUS: Radar View of Surface Quark’s Holiday Tour No rivers, oceans Surface 500°C - greenschist metamorphism No plate tectonics - only hot spot volcanism N. Lindsley-Griffin, 1998

VENUS: Mountains and Faults Quark’s Holiday Tour Linear features are tension cracks (normal faults) Structures are horsts and grabens like the Basin and Range Province Form over rising or sinking mantle plumes N. Lindsley-Griffin, 1998 Normal Faults Grabens

VENUS: Volcanoes, Lava Flows Quark’s Holiday Tour Radar images show large shield volcanoes Entirely basaltic crust - no granite Fresh, uncratered lava flows N. Lindsley-Griffin, 1998 Sif Mons, a shield volcano Bright radar images are rough aa lava Dark lava flows are smooth, less reflective, pahoehoe lava

Maat Mons Volcano, Venus The entire surface of Venus is covered by 500 m.y. basalt Suggests a catastrophic resurfacing event Sparse impact crater density -little modification since then Older Lava Flow Younger Lava Flow Younger Impact Crater N. Lindsley-Griffin, 1998

MERCURY Quark’s Holiday Tour Closest planet to Sol Smaller than all other planets except Pluto No atmosphere Rotates only 3 times in 2 of its years N. Lindsley-Griffin, 1998

MERCURY: Geology Quark’s Holiday Tour Surface very old, heavily cratered, similar to Luna Huge lava plains like Lunar maria N. Lindsley-Griffin, 1998

Sol: Close Approach Quark’s Holiday Tour As we zoom around Sol on our way to Terra…. N. Lindsley-Griffin, 1998 Dark sunspots are relatively “cool” regions Solar flare or prominence

TERRA - LUNA Quark’s Holiday Tour The moon Luna is 1/4 the diameter of Terra Some scientists consider these to be paired planets like Pluto - Charon Luna’s relatively great mass affects ocean tides on Terra N. Lindsley-Griffin, 1998

LUNAR GEOLOGY Quark’s Holiday Tour Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 Terrae, or lunar highlands (red color), the older crust under basalt lava flows Maria, or lunar lava flows, (blue and orange color) are the younger lowlands Tycho crater: Rays of young ejecta cut across older features

LUNAR METEORITE IMPACT Quark’s Holiday Tour Large crater excavated by impact. Meteorite disintegrates, debris scatters all around. Secondary craters formed by impact of larger ejecta fragments. Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999

ORIGIN OF LUNAR MARIA Impact forms normal faults and ring fractures around crater Basaltic magma forms by pressure-release melting, ascends through fractures to fill crater. Result: younger, less cratered basaltic maria. Houghton-Mifflin, Dolgoff, 1998; N. Lindsley-Griffin, 1999 LUNAR METEORITE IMPACT Quark’s Holiday Tour

Crater Density and Age of Surface Many craters on older, original lunar crust (anorthosite brecciated by repeated impacts) Fewer craters on younger crust of basalt in the lunar mare (dark colored basins) Crater density provides relative dating for lunar surfaces N. Lindsley-Griffin, 1999 LUNA Quark’s Holiday Tour B A CD b.y. ago Crater Density (arbitrary units)

TERRA: Unique! Quark’s Holiday Tour Oxygen-rich atmosphere Over 70% surface is water Plate tectonics recycles oxygen and water Only known life in Solar System (but is it intelligent?) N. Lindsley-Griffin, 1998

TERRA: Intelligence? Quark’s Holiday Tour Hope for the future: The U-manz (Terrans) are building a space station. - a primitive step towards exploring the universe - people and nations who were enemies not long ago are working together. Let’s hope they finish growing up before they invade us! N. Lindsley-Griffin, 2000

THAT CONCLUDES OUR TOUR Enjoy your Holiday! Quiz pts. extra credit over the locations on this tour of the solar system - will be active until 5:00 PM Wednesday Dec. 13 N. Lindsley-Griffin, 1998