Lecture Outlines Physical Geology, 14/e Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Plummer, Carlson & Hammersley

The Earth’s Companions Physical Geology 14/e, Chapter 23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Earth – one of eight planets that orbit the Sun in our solar system Sun – has no solid surface, but rather is a huge ball of very hot gas 75% H, 25% He overwhelming majority of mass in the solar system is in the Sun hydrogen is fusing into helium in the core of the Sun, releasing energy in the form of sunlight gravity associated with Sun’s huge mass holds planets, asteroids, and comets in their orbits Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Earth in Space

All of the planets orbit the Sun in the same direction counterclockwise when viewed from above Earth’s north pole Orbits of all planets lie within 7 degrees of the plane of Earth’s orbit around the Sun solar system is distinctly disk-shaped Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Solar System

Inner planets – small, rocky, include Mercury, Venus, Earth, Mars Outer planets – huge, include Jupiter, Saturn, Uranus, Neptune Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Solar System

Asteroids – rocky or metallic objects, ~ 1000 km or less in diameter most lie in the asteroid belt between the orbits of Mars and Jupiter Comets – icy bodies, ~1000 km or less in diameter found in two reservoirs, the Kuiper Belt and the Oort Cloud Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Small Bodies in the Solar System

Nebular hypothesis – the solar system originated from a rotating, flattened disk of gas and dust known as the solar nebula observed compositional trend from metal and rock in the inner solar system, to gases and ices in the outer solar system, supports hypothesis Sun, Moon, Earth, and meteorites all appear to have same age (about 4.6 billion years) suggesting they formed in a single event Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin of the Planets

Planetesimals – formed from dust clumped together which further clumped into planets gravity drives process differentiation Moons – originated by clumping of rings of debris around planets or by gravitational capture Atmospheres – formed either by gravitational capture of gases or from volcanic eruptions and cometary impacts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Formation of Planets & Moons

Moon – Earth’s only natural satellite, possesses no air, water or life, about ¼ the diameter of Earth heavily cratered, ancient surface records impact events for nearly the entire history of the solar system lava flows and channels observed currently no volcanic, tectonic, or weathering activity likely origin was catastrophic impact Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Earth’s Moon

Mercury – smallest inner planet, resembles Earth’s Moon in both size and appearance no atmosphere density suggests very large iron core heavily cratered, but with smooth plains and scarps Venus – hottest planetary surface in the solar system (>480° C) CO 2 atmosphere creates greenhouse effect abundant volcanoes and lava flows fractures and mountain belts suggest intense tectonic activity relatively low number of impact craters suggests recent or ongoing surface processes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mercury & Venus

Mars – diameter 1 / 2 of Earth thin CO 2 atmosphere (less 1% as thick as Earth’s) red color results from oxidized iron-rich surface frozen water and CO 2 ice polar caps abundant volcanoes and lava flows fractures and canyons suggest tectonic activity dune fields and dust storms indicate wind activity eroded channels suggest flowing water in past current conditions at surface not hospitable for life, but evidence of flowing water in past suggests a warmer and thicker atmosphere in ancient times Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mars

Show a progression of increasing geologic activity, both in the past and today, directly related to their size Water and ice more abundant on Earth and Mars Biological processes on Earth produced oxygen-rich atmosphere and abundant plants drastically affect surface conditions and weathering processes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Differences in the Terrestrial Planets

Jupiter – largest planet in the solar system composed of hydrogen and helium gases, with a small ice/rock core atmospheric clouds are composed of methane, ammonia and water ices high pressure deep in the interior, results in hydrogen compressed first into liquid, then into a liquid metal Jupiter’s largest moons: Europa, Ganymede, Io Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Jupiter

Saturn – second-largest planet in solar system, composed of hydrogen and helium gases, with small ice/rock core spectacular ring system of chunks of ice and rock largest moon, Titan Uranus – composed largely of hydrogen and helium, with small rock/ice core rotational axis and moons’ orbits tipped on side moon Miranda has unique landforms Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Saturn & Uranus

Neptune – similar in size and composition to Uranus largest moon, Triton, has ice volcanoes Pluto – recently demoted to dwarf planet status largest icy object in solar system Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neptune & Pluto

Asteroids – small, rocky bodies that orbit the Sun most lie in asteroid belt between orbits of Mars and Jupiter Meteorites – probably represent fragments of asteroids Comets – small, icy bodies that orbit the Sun Giant impacts – periodically occur when Earth sweeps up one of these remnants from formation of the solar system Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Asteroids, Comets, & Meteorites

End of Chapter 23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.