Comparing Inner Planets: Cratering, Volcanoes, and Age - Prof. Jason Jackiewicz, Quizzes of Astronomy

Download Comparing Inner Planets: Cratering, Volcanoes, and Age - Prof. Jason Jackiewicz and more Quizzes Astronomy in PDF only on Docsity! Lecture 19 Geological Comparison of the Inner Planets ASTR 105G: The Planets April 2, 2009 Announcements 1. quiz today 2. Surface of the Moon lab today, read it, and bring your last lab to turn in 3. Exam Tuesday April 14 4. Observatory open house friday night at 9pm 5. Extra credit opportunity! Sunday April 26, Dr. Steve Squyres, Corbett Center, Mars Rover PI Last time ... • We talked about how important the size of a planet is for heating and cooling (and everything else) • Magnetic fields • Surface-changing processes: erosion, tectonics, cratering, volcanism • Size, distance from the Sun, and rotation rate basically determine everything about the terrestrial planets How Do We Learn Anything From These 4 Processes • The amount of craters tell us the geological activity of a planet • Volcanic activity “erases” evidence of craters • We can then “date” a planet’s surface age 1 Terrestrial Geology 1.1 Moon and Mercury Which is Which? Source of Figure 1: http://en.wikipedia.org/wiki/Image:The Moon Luc Viatour.jpg Source of Figure 2: http://en.wikipedia.org/wiki/Image:Mercury in color - Prockter07 centered.jpg Lecture 19 April 2, 2009 2 / 7 Figure 1: The Moon. Lecture 19 April 2, 2009 5 / 7 Evidence for Water (Erosion) • Too cold today for liquid water • But what about this!?3 • The surface conditions must have been much different in the past • Any water today is frozen as ice in the soil or the polar caps Missions Rovers landed in 2004: • Spirit - in a crater4 • Opportunity - in the plains5 ... still going strong and exploring. Check out this site6 Life on Mars? • No ozone layer so the ultraviolet light reaches the ground • Whatever is living there must be underground • Like him!7 1.3 Venus Different Views of Venus Source of Figure 3 is Nick Strobel’s www.astronomynotes.com Basics Very similar to Earth in many ways. But ... • Sparse and evenly-distributed craters • Not many small ones because atmosphere burns them up • Many lava plains and and volcanoes • The atmosphere is filled with the gases that volcanoes emit • No evidence of erosion because it rotates slowly and too hot for rain • No evidence of plate tectonics today, but certainly in the past (weaker mantle convection?) • Maybe a harder lithosphere because no water to soften it 3http://astronomynotes.com/solarsys/pics/mars-networksm.jpg 4http://astronomynotes.com/solarsys/spirit-site.htm 5http://astronomynotes.com/solarsys/opportunity-site.htm 6http://marsrovers.jpl.nasa.gov/mission/traverse maps.html 7http://healthcare.zdnet.com/images/ray-walston-as-my-favorite-martian.jpg Lecture 19 April 2, 2009 6 / 7 Figure 3: Venus imaged in ultraviolet light from Pioneer (left) and in radar from the Magellan spacecraft (right). 1.4 Earth Tectonics • Tectonic plates are fractured pieces of the lithosphere due to stresses by convection • Map of the plates8 • See Figure 9.45 • We know this happens because of convection? How does it happen? The Role of the Sea and Moving Plates • Earth has two types of crust • Seafloor crust is thin and dense, 5-10 km thick, and young • Continental crust is thicker and less dense, 20-70 km thick • Seafloor crust is constantly forming from mantle material rising and cooling • It slides along the mantle colliding with continental crust and gets recycled back into the mantle by subduction9 • Also seafloor spreading10 8http://astronomynotes.com/solarsys/earth-plates.gif 9http://www.wwnorton.com/college/geo/egeo/flash/2 9.swf 10http://www.wwnorton.com/college/geo/egeo/flash/2 5.swf Lecture 19 April 2, 2009 7 / 7 • Structures form from colliding plates11 Example - North America Satellite image12 • The west coast places were long ago volcanic islands in the Pacific Ocean that attached themselves to the mainland • The Midwest was once a great sea or seas that erosion slowly filled in with sediment • The mountains of California are due to subduction of plates underneath the west coast • The Appalachian mountains are due to colliding pieces of continent, and have been eroded substantially • Hawaii, a chain of extinct volcanoes, is formed from being over a hotspot13 For next time ... 1. We will talk about atmospheres of the inner planets 11http://astronomynotes.com/solarsys/plates-collide.png 12http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/North America satellite orthographic.jpg/557px- North America satellite orthographic.jpg 13http://www.wwnorton.com/college/geo/egeo/flash/2 10.swf