Lecture 12: Planetary Geology There are two major types of planets Terrestrial planets versus Jovian-sized planets Will focus on terrestrial planets Overview of Common Characteristics of the Terrestrial Planets Have relatively high surface temperatures - Located close to the sun (2) Have high densities (3) Are relative small compared with Jovian-sized planets (4) Have thin or no atmospheres compared with Jovian planets (5) Have few or no moons compared …

The Terrestrial Planets

Planet #1 - Mercury: Craters

Some Characteristics of Mercury Planet #1 No Moons Geologically dead - Probably for the last 3 b.y. No significant atmosphere or hydrosphere Heavily cratered - Why?

Some Venus Facts Planet #2 No Moons Geologically active - Has both volcanoes and mountain building - Has “Venus”quakes and active fault zones

Mountains on Venus

FAULT VALLEYS ON VENUS

Volcanoes on Venus

Venus: Cloud Deck

SOME FACTS ABOUT VENUS’ ATMOSPHERE Sulfuric acids rains in the upper atmosphere Surface temperature of 450 C Atmospheric pressure at the surface of 90 bars Atmosphere consists of mainly carbon dioxide (CO2 - 97.5%)

The Earth: Planet #3 We do have a Moon

Brief history of the Moon: Formed 4.5 b.y. ago - When a Mars-sized body impacted the earth and ejected material into earth’s orbit At 4.5 b.y. the original lunar crust formed (The Lunar Highlands) - Igneous rock Between 4.1 to 4.5 b.y. ago this crust was heavily bombarded by Asteroids From 3.1 to 4.1 b.y. massive volcanic activity took place forming the lunar maria (Flatlands or face in the man on the moon) At 3.1 b.y. ago the moon solidified and essentially became geologic dead

In the Beginning: Massive Collision

How do we know this much about the moon? Moon rocks

The Red Planet: Mars

Some Characteristics of Mars Planet #4 Two Small Moons (really just asteroids) Thin atmosphere (not breathable) No oceans or water on the surface - But below the surface???

Deimos: One of Mars’ Tiny Moons

MARS: MONS OLYMPUS

Planet #4 - Mars What can you infer about geologic activity on Mars? - Any active volcanoes today on Mars? - No - But, in the not so distant geologic past there were volcanoes? - About 1 b.y. ago

Asteriod: Solidified in 100 m.y. Activity Complete by 4.5 b.y. ago Mass <0.001 Earth Moon: Solidified in 1.5 b.y. Activity Complete by 3.1 b.y. ago Mass = 0.016 Earth Mars: Solidified in 3 to 4 b.y. Activity Complete by ≈ 1 b.y. ago Mass = 0.11 Earth

GENERAL PRINCIPLE OF TERRESTRIAL PLANETARY DEVELOPMENT The bigger the planetary body the longer it takes to cool. Geological activity (volcanoes, mountain building) will occur over a greater duration when planetary bodies are larger! YOU MUST be able to compare at the duration of geological activity for bodies such as asteroids, the moon, Mars, and the earth

What about the prospects for life on the Martian surface today?

Have pieces of Mars on Earth The Martian meteorites

The fossilized Martians?????

Overview of Common Characteristics of the Jovian Planets (Planets 5 to 8) Have relatively low surface temperatures - Located far from the sun (2) Have low densities Are large in their diameter compared with terrestrial- sized planets Have extremely thick atmospheres - Essentially are large gas balls Have many moons compared with terrestrial sized planets - Can be thought of as mini-solar systems

Jupiter (Planet #5): The largest planet in the solar system

Icy Balls: Ganymede a typical moon around a Jovian planet Not like the rocky moon that we have around the earth!

And what of Pluto (Planet #9 ?)