The Solar System Terrestrial Planets Earth Average distance

The Solar System

Terrestrial Planets

Earth • Average distance from the Sun: 1. 00 AU • Radius: 6, 378 km • Mass: 5. 97 × 1024 kg • Avg. density: 5. 52 g/cm 3 • Composition: rocks, metals • Average surface temperature: 290 K • Satellites: 1

Earth’s Structure • Core – highest-density material, mostly Ni & Fe • Mantle – moderate density, mostly Si, O, etc. • Crust – lowest-density rock, granite & basalt

Structure

Internal Heat Formation Geological Activity • Caused by accretion and collisions during formation • Also due to radioactive material • Convection and Cooling • Differentiation

Magnetic Field • Caused by the motion of charged particles in Earth’s molten outer core • Magnetosphere protects us from solar wind

Shaping Earth’s Surface • Cratering • Volcanism • Tectonics • Erosion

Earth’s Atmosphere • 77% N 2, 21% O 2 • Protection – X-rays are absorbed high up in the atmosphere – Ozone absorbs UV – Visible light gets through no problem

Earth’s Atmosphere Scattering • Blue light is scattered more easily than red light • Sky is blue because sunlight gets scattered to your eye from all directions • Sun look red at sunrise/set because blue light gets scattered away

5800 K Greenhouse Effect Visible Light 300 K CH 4 IR Light H 2 O CO 2 Ground

Geologically Dead Objects

The Moon • Average distance from the Earth: 384, 000 km • Radius: 1, 700 km • Mass: 7. 3 × 1022 kg • Avg. density: 3. 35 g/cm 3 • Period: 29. 5 days

Geological Features Lunar Maria Micrometeorites

Mercury • Average distance from the Sun: 0. 39 AU • Radius: 2, 440 km = 0. 38 REarth • Mass: 0. 055 MEarth • Avg. density: 5. 43 g/cm 3 • Composition: rocks, metals • Average surface temperature: 700 K day, 100 K night • Satellites: 0 • 88 day orbit, 59 day rotation

Geological Features One giant crater called “Caloris Basin”

Mars • Average distance from the Sun: 1. 52 AU • Radius: 3, 397 km = 0. 53 REarth • Mass: 0. 11 MEarth • Avg. density: 3. 93 g/cm 3 • Composition: rocks, metals • Average surface temperature: 225 K • Satellites: 2

Mars vs. Earth Similarities Differences • Day is about 25 hours long • More extreme seasons in southern hemisphere • Polar caps contain CO 2 • Only about 1% of Earth’s atmosphere, which is CO 2 • Much colder • Polar caps • Axis tilted about the same Perhaps it was more similar long ago

Martian Geology

Martian Geology • Polar ice caps • Higher elevation of southern hemisphere • Lack of craters in northern hemisphere • Tharsis Bulge, Valles Marineris

Martian Geology • Olympus Mons – The largest volcano in the solar system – Base covers an area equal to Arizona – 26 km above average surface level, 3 x the size of Mt. Everest

Water on Mars • Today the surface temperature and pressure to too low for liquid water • Polar caps • Ground water • Evidence of ancient H 2 O – Dried Riverbeds • Maybe not – Signs of erosion

What happened?

Venus • Average distance from the Sun: 0. 72 AU • Radius: 6, 51 km = 0. 95 REarth • Mass: 0. 82 MEarth • Avg. density: 5. 24 g/cm 3 • Composition: rocks, metals • Average surface temperature: 740 K • Satellites: 0

Venusian Geology • Craters, volcanoes, tectonics somewhat similar to Earth • Coronae – bulges made by hot, rising plumes of mantle • No plate tectonics

Venusian Atmosphere • Atmosphere about 90 x as thick as Earths • Made up of about 96% carbon dioxide, but virtually no water • Why should the atmosphere be different from Earth’s?

Why are the atmosphere’s different? Earth Venus • Water rained into oceans • Lacking water • CO 2 dissolved into water and then formed into carbonate rocks – Including the rocks, Earth has about as much carbon dioxide as Venus – Explains why there is more carbon dioxide in the atmosphere: cannot dissolve and become rock • Where did the water go? – UV light breaks up molecule

Runaway Greenhouse Effect

Life What is necessary?

A few examples • Liquid Water • Atmospheric Oxygen • Climate Stability • Planetary Size – Must be large enough so it doesn’t cool too quickly, preventing tectonics • Distance from Sun – Liquid Water

The CO 2 Cycle

Global Climate Change

Global Climate Change