Chapter 22: Planetary Geology

Chapter 22: Planetary Geology

IntroductionIntroduction Compositional Groups:

Gases: H & He Melting points near absolute zero (-273°C)

Rocks: Silicate minerals & Fe-Ni metal Melting points >700°C

Ices: Composed of Ammonia (NH3), Methane (CH4), CO2 &

H2O Intermediate melting points

Compositional Groups: Gases:

H & He Melting points near absolute zero (-273°C)

Rocks: Silicate minerals & Fe-Ni metal Melting points >700°C

Ices: Composed of Ammonia (NH3), Methane (CH4), CO2 &

H2O Intermediate melting points

The PlanetsThe Planets Inner Planets:

AKA Terrestrial Planets (like Earth) AKA Rocky Planets

Dominated by rocky materials Mercury, Venus, Earth, Mars

Outer Planets: AKA Jovian Planets (like Jupiter) Gas Giants: Jupiter & Saturn Ice Giants: Uranus & Neptune + Pluto (Rocky-Ice planet?)

Minor Planets: Asteroids, Comets & Kuiper Belt Objects

Inner Planets: AKA Terrestrial Planets (like Earth) AKA Rocky Planets

Dominated by rocky materials Mercury, Venus, Earth, Mars

Outer Planets: AKA Jovian Planets (like Jupiter) Gas Giants: Jupiter & Saturn Ice Giants: Uranus & Neptune + Pluto (Rocky-Ice planet?)

Minor Planets: Asteroids, Comets & Kuiper Belt Objects

Planetary DataPlanetary Data

Planetary AtmospheresPlanetary Atmospheres Ability to hold onto an atmosphere

depends on planet’s mass & temperature Escape velocity: minimum velocity to

escape the gravity of a plant e.g. Earth’s escape velocity = 11 km/s

Ice line: distance from Sun that is cold enough for water ice to be stable

Giant planets have thicker atmospheres b/c formed past ice line & therefore accreted ices & rock

Inner planets have thinner atmospheres b/c accreted only rock

Ability to hold onto an atmosphere depends on planet’s mass & temperature

Escape velocity: minimum velocity to escape the gravity of a plant e.g. Earth’s escape velocity = 11 km/s

Ice line: distance from Sun that is cold enough for water ice to be stable

Giant planets have thicker atmospheres b/c formed past ice line & therefore accreted ices & rock

Inner planets have thinner atmospheres b/c accreted only rock

MercuryMercury Low albedo

Reflects only 5% of sunlight

Has highly-crated highlands & smooth terraines similar to Moon

Highly eccentric orbit 46-70 million km

High density Implies large core

Tidally locked to Sun 3:2 resonance 3 days to 2 years

Low albedo Reflects only 5% of

sunlight Has highly-crated

highlands & smooth terraines similar to Moon

Highly eccentric orbit 46-70 million km

High density Implies large core

Tidally locked to Sun 3:2 resonance 3 days to 2 years

Irregularities in Mercury’s orbit helped to prove Einstein’s General Theory of Relativity

Irregularities in Mercury’s orbit helped to prove Einstein’s General Theory of Relativity

http://www.nineplanets.org/mercury.html

VenusVenus High albedo

Due to high cloud cover

Second brightest object in night sky

Nearly circular retrograde orbit

Thick atmosphere 90 atm ~470°C (melt Pb)

Pancake volcanoes

High albedo Due to high cloud

cover Second brightest

object in night sky Nearly circular

retrograde orbit Thick atmosphere

90 atm ~470°C (melt Pb)

Pancake volcanoes

Considered Earth’s twin 95% Earth’s

diameter 80% Earth’s mass Young surfaces Same bulk chemistry

& density

Considered Earth’s twin 95% Earth’s

diameter 80% Earth’s mass Young surfaces Same bulk chemistry

& density

Radar Map

Venusian Surface

http://www.nineplanets.org/venus.html

Earth-Moon SystemEarth-Moon System

Brightest object in night sky

Two types of terraines: Ancient highlands

~ Feldspar Younger Maria

~ Basalt Low density (~3.3 g/cm3)

Implies little or no core Formation by large

impact ~Mars-sized object Explains O-isotopes, low

density & chemical composition

Brightest object in night sky

Two types of terraines: Ancient highlands

~ Feldspar Younger Maria

~ Basalt Low density (~3.3 g/cm3)

Implies little or no core Formation by large

impact ~Mars-sized object Explains O-isotopes, low

density & chemical composition

http://www.nineplanets.org/moon.html

cygnus.colorado.edu

MarsMars 1% Atm of Earth

CO2 rich

Ice caps (H2O & CO2) Evidence of liquid water Has highest mt. &

longest, deepest valley in Solar System

1% Atm of Earth CO2 rich

Ice caps (H2O & CO2) Evidence of liquid water Has highest mt. &

longest, deepest valley in Solar System

Phobos

Deimoshttp://www.nineplanets.org/mars.html

Viking Image

Pathfinder Image

JupiterJupiter

Largest planet in Solar System Bands of clouds & storms

Convection of atm Radiates more heat than

receives from Sun Rotates in 10 hours At least 28 moons

Largest planet in Solar System Bands of clouds & storms

Convection of atm Radiates more heat than

receives from Sun Rotates in 10 hours At least 28 moons

Io http://www.nineplanets.org/jupiter.html

Europa

SaturnSaturn Second largest planet in

Solar System Has well-developed ring

system Bands & storms

Similar to Jupiter’s At least 30 moons,

including “sheppard moons” Titan has thick atmosphere

Second largest planet in Solar System

Has well-developed ring system

Bands & storms Similar to Jupiter’s

At least 30 moons, including “sheppard moons” Titan has thick atmosphere

Titan

http://www.nineplanets.org/saturn.html

Mimas

UranusUranus

Twin with Neptune Slightly larger in

diameter Slightly smaller in mass

Rotates 90° to orbit around Sun

At least 15 moons Miranda shows greatest

At least 9 rings

Twin with Neptune Slightly larger in

diameter Slightly smaller in mass

Rotates 90° to orbit around Sun

At least 15 moons Miranda shows greatest

At least 9 rings

Miranda

Rings

http://www.nineplanets.org/uranus.html

NeptuneNeptune Twin with Uranus Blue due to methane in

atmosphere Bands & storms

Giant Dark Spot has disappeared

At least 13 moons Triton has atmosphere

Retrograde orbit Similar in reflectance spectra

to Kuiper Belt Objects & Pluto Ice volcanoes

Twin with Uranus Blue due to methane in

atmosphere Bands & storms

Giant Dark Spot has disappeared

At least 13 moons Triton has atmosphere

Retrograde orbit Similar in reflectance spectra

to Kuiper Belt Objects & Pluto Ice volcanoes

Triton

http://www.nineplanets.org/neptune.html

Pluto-Charon SystemPluto-Charon System

Highly eccentric & inclined orbit

Highest satellite:planet radius ratio

Similar reflectance spectra to Kuiper Belt Objects Also to Centaurs &

primitive asteroids

Highly eccentric & inclined orbit

Highest satellite:planet radius ratio

Similar reflectance spectra to Kuiper Belt Objects Also to Centaurs &

primitive asteroids Charonhttp://www.nineplanets.org/pluto.html

HST image

HST image

Minor PlanetsMinor Planets Asteroids:

Mostly between Mars & Jupiter Kuiper Belt Objects:

AKA Trans-Neptunian Objects Discovered in 1992 Source of Short-Period Comets

Oort Cloud Comets: Spherical Cloud on edge of Solar System Theoretical, proposed in 1950 Source of Long-Period Comets

Asteroids: Mostly between Mars & Jupiter

Kuiper Belt Objects: AKA Trans-Neptunian Objects Discovered in 1992 Source of Short-Period Comets

Oort Cloud Comets: Spherical Cloud on edge of Solar System Theoretical, proposed in 1950 Source of Long-Period Comets

AsteroidsAsteroids First discovered in 1801

Named Ceres Several hundred thousand

have been discovered Several 1000

discovered each year Classified by composition

& albedo 75% are C-type

Darkest, C-rich 17% are S-type

Moderate, metal + silicates

5% are M-type Brightest, mostly metal

First discovered in 1801 Named Ceres

Several hundred thousand have been discovered Several 1000

discovered each year Classified by composition

& albedo 75% are C-type

Darkest, C-rich 17% are S-type

Moderate, metal + silicates

5% are M-type Brightest, mostly metal Itokaw

a

243Ida

951Gaspara 253Mathild

e

433Eros

http://near.jhuapl.edu/iod/20000214f/index.html

http://www.psi.edu

http://www.nineplanets.org/asteroids.html

Kuiper Belt ObjectsKuiper Belt Objects

Sedna

http://hubblesite.org/newscenter/archive/releases/2004/14/image/a

en.wikipedia.org/wiki/50000_Quaoar

Quaoar

Oort Cloud CometsOort Cloud Comets

~50,000 AU from Sun ~ 1 light year

Source of long period comets > 200 years

Materials scattered out from interaction with Jupiter & Saturn

~50,000 AU from Sun ~ 1 light year

Source of long period comets > 200 years

Materials scattered out from interaction with Jupiter & Saturn

www.solstation.com www.wikipedia.co

m

gatornet.chapin.edu

www.britannica.com

Meteorites: Time CapsulesMeteorites: Time Capsules Nebula Heterogeneous Formation Sequence

CAIs, Chondrules, fine-grained materials Some melted Some wet Some hot Some both hot & wet Organic materials present

Nebula Heterogeneous Formation Sequence

CAIs, Chondrules, fine-grained materials Some melted Some wet Some hot Some both hot & wet Organic materials present

Meteorite ClassificationMeteorite Classification

Metallic Basaltic Pallasites

Igneous

Achondrites

Carbonaceous Ordinary Enstatite

Primitive

Chondrites

Metallic Basaltic Pallasites

Igneous

Achondrites

Carbonaceous Ordinary Enstatite

Primitive

Chondrites

Chondritic ~ Solar Composition

Chondritic ~ Solar Composition

Martian MeteoritesMartian Meteorites Are probably from Mars b/c:

Young & basaltic Recent volcanism (130 to 1300 Ma)

O-isotopes: if one from Mars, all from Mars

Gas bubbles trapped in glass Composition ~ Viking measurements N2, CO2, H2, He, Ar, Kr, Xe & isotope

ratios

Are probably from Mars b/c: Young & basaltic

Recent volcanism (130 to 1300 Ma) O-isotopes:

if one from Mars, all from Mars Gas bubbles trapped in glass

Composition ~ Viking measurements N2, CO2, H2, He, Ar, Kr, Xe & isotope

ratios

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Carbonate Globbules

Also: PAHs

~900oC or <80oC ?

~ Antarctic meltwaterNot spatially near CO3’s

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Orange: Ca, Mn-richInner Black: Mg-rich

White: Fe-richOuter Black: Fe, S-rich

(where mt is)

Life on Mars?Life on Mars?

Oxygen IsotopesOxygen Isotopes

Life on Mars?Life on Mars?

SEM prep artifact?

Too small for DNA?

Terrestrial contamination

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Shergotty

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Life on Mars?

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ALH84001 Terrestrial

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Etched Volcanic GlassEtched Volcanic Glass