Basic Properties and Remote Sensing

 Density:

 

 

 

 

 

Mass - amount of matter - grams

Volume - cubic centimeters

Density - mass/volume - g./cc. (454 g/pound)

(fl. oz. = 29.6 cc)

Density: Water = 1.0 g/Cc

Alcohol = 0.8

Typical rock = 2.7     (on Earth's surface)

Iron = 7.6     (Inside Earth)

Lead = 11.3

Earth (ave.) = 5.5

Moon (ave.) = 3.4

Terrestrial Planets - close to sun: Mercury, Venus, Earth, Mars - Small thin or no atmospheres, few or no moons

Jovian (Gas Giant) Planets: Jupiter, Saturn, Uranus, Neptune - large massive atmospheres many icy moons

Pluto: Planetessimal, similar to icy moons of Jovians

 

 

 

Chemistry of Planets

 

Four types of matter:

 

Gas: Jovian Planets, solar nebula , H    He   CO2   CO     NH3      CH4

 

Ice: inner solar system - water, CO2   outer ss moons - CO     NH3      CH4

Rock: silicates, oxides of silicon, aluminum, magnesium are most common

Metal: iron, nickel, magnesium - mostly in planetary cores

 

Rocks and Minerals

 

Minerals

The principal difference - homogeneity.

 

 Mineral - a single substance

 

 Rock - several different minerals

 

Gold and silver -most famous examples of single‑element minerals in the U S

 

Also, elemental sulfur, copper, and carbon (graphite and diamonds)

 

Single compound minerals more common. Quartz (Si O2), hematite 

(Fe2O3), iron pyrite or "fool's gold" (FeS2), and calcite (CaC03)

 

Rocks:

                  

Igneous rocks formed directly by cooling from a molten state, e.g., basalts

 

Sedimentary rocks - frag­ments of other rocks cemented together, often under water

 

Metamorphic rocks -either igneous or sedimentary rocks buried far below the Earth's surface, modified by the high pressures and temperatures, then returned to surface, e.g., marble.

 

Primitive Rocks: Never melted, affected chemically or physically.

Not found on Earth, e.g., meteorites

 

Reason: larger bodies accumulate and generate heat faster than radiate it away.

Planet gets hotter - energy from accretion and radioactive decay Ž differentiation

 

V=4/3 p R3                   A=4 p R2

Planetary Atmospheres-Reducing and Oxidizing

 

Hydrogen - reducing, light molecule, held by large planets far from sun

Oxygen - oxidizing, heavier molecule, smaller planets closer to sun

 

Two ways to obtain an atmosphere:

 

Primordial - captured solar nebula gasses, (mainly H and He - light molecules, also  CO2   CO     NH3      CH4 )   also, comet strikes

 

Secondary or outgassed - released from rocks, volcanoes

 

Combination of first  two - especially Jovian planets - H and He from SN, others from core

 

Capturing and Holding the atmosphere:

 

Gas motion less than escape velocity  -

Determined by gravity & temperature of planet

 

Only solid matter, ices and rock, form solid planetary core (determines gravity) Rock (refractory, high melting point, material) small % of total mass available

 

Majority of mass as volatiles - low melting point - gasses in inner SS, ices outer SS

 

Inner SS: Temp high - only refractory elements solid - planet mass low (can't capture or hold H and He, ) Ž H,  He escape

 

Outer SS: Temp lower, cores include refractory and ices Ž cores more massive 

Capture and hold H and He - adds to mass - captures even more gas, etc.

 

 

Remote sensing

Spectroscopy

 

Use absorption lines from planetary atmosphere in reflected solar spectrum (Includes solar absorption lines)

 

Albedo: % reflected sunlight

 

Infrared spectrum (emitted from planet surface): absorption lines from planet (and Earth) only

 

Compare reflected solar to emitted infrared spectrum for planetary absorption lines