Impact Cratering MARS EDUCATION PROGRAM David A. Hardy Impact cratering overview: What we will learn about impact craters today: • Causes of impacts - meteorites! • Impact craters in our solar system • Formation of craters • Different parts of a crater • How do craters can change over time • Craters as dating tools MARS EDUCATION PROGRAM • Meteorites on Mars Leonid Meteor Shower Spain November 2002 MARS EDUCATION PROGRAM Juan CarlosCasado Meteor or “shooting star” is the visible path made by a object from space as it travels through a planet’s atmosphere. MARS EDUCATION PROGRAM Sophie DesRosiers, Planétarium de Montréal Meteor or meteorite? QuickTime™ and a YUV420 codec decompressor are needed to see this picture. S. Eichmiller StarChild, NASA Meteorite breaking up as it travels through the atmosphere Peekskill Meteorite October 9, 1992 Peekskill, New York MARS EDUCATION PROGRAM Bill Menke Meteorites are objects from space (meteoroids) that reach a planet’s surface. Iron meteorite Boy hit by a meteorite Arizona Uganda, Africa R.A. Langheinrich Meteorites Collection Dutch Meteor Society MARS EDUCATION PROGRAM Rudolf Reiser Largest meteorite discovered on Earth Namibia, Africa What are meteoroids? Pieces of other Space planets dust Meteoroids NASA/JPL Comets Cécile Engrandare particles of rock, metal and/or ice in space. MARS EDUCATION PROGRAM NASA/JPL Asteroids Rudolf Reiser Most meteoroids are materials left over from the formation of our solar system 4.5 billion years ago! MARS EDUCATION PROGRAM Don Dixon Where do most asteroids come from? Asteroid Belt Ida MARS EDUCATION PROGRAM NASA/JPL Where do most comets come from? Halley’s comet Max-Planck-Institut fur Aeronomie MARS EDUCATION PROGRAM NASA/JPL What happens when a large meteoroid hits a planet? MARS EDUCATION PROGRAM Andrew C. Stewart MARS EDUCATION PROGRAM Why are they important? Meteor Crater, Arizona How do craters form? Impact craters are formed! USGS THEMIS Image, Mars NASA/JPL/ASU Earth’s Moon MARS EDUCATION PROGRAM NASA/JPL Mercury MARS EDUCATION PROGRAM NASA/JPL Mars MOLA topographic map MARS EDUCATION PROGRAM NASA/JPL Mimas, moon of Saturn Herschel Crater Evidence of giant impacts! MARS EDUCATION PROGRAM NASA/JPL Are there impact craters on Earth? MARS EDUCATION PROGRAM Sophie DesRosiers, Planétarium de Montréal Lonar Impact Crater India Impact Craters on Earth Manicouagan Impact Crater Quebec, Canada Google Earth Wolf Creek Impact Crater N Western Australia, Australia MARS EDUCATION PROGRAM Ronald W. Hayes, USGS David McKinnon Best preserved impact crater on Earth! Holsinger meteorite (1400 lbs) Meteor Crater Winslow, Arizona Impact 50,000 years ago MARS EDUCATION PROGRAM Geoscience Research Institute Martin Hellman Sophie DesRosiers, Planétarium de Montréal Chicxulub impact crater Yucatán Peninsula Impact 65 million years ago Gravitational anomaly map MARS EDUCATION PROGRAM NASA / LPI / V.L. Sharpton MARS EDUCATION PROGRAM Lunar and Planetary Institute How do impact craters form? Cinder Lakes Flagstaff, Arizona MARS EDUCATION PROGRAM Meteorites impact on Mars! Crater Formation: Meteoroid Planet surface Planet surface 1. Meteoroid traveling 10-15 kilometers/second strikes the surface of a planet Ejecta 2. Shock waves compress the rocky surface and the Shock waves Contact - Compression meteoroid is vaporized MARS EDUCATION PROGRAM Sophie DesRosiers, Planétarium de Montréal Crater Formation: Ejecta Planet surface 3. Intense shock waves travel through the ground, breaking up and melting surrounding Shock waves rock Molten rock Crater Vapor Ejecta curtain Excavation 4. Crater is formed as shock waves and ejecta expand Shock waves outward MARS EDUCATION PROGRAM Sophie DesRosiers, Planétarium de Montréal Crater Formation: Ejecta 5. Shock waves die out and ejecta settles forming a Fractured rock blanket around the crater rim Fractured rock Ejecta blanket Uplifted Breccia rim Modification 6. Crater is fully formed and is modified by gravity, erosion and sedimentation over Fractured rock geologic time. MARS EDUCATION PROGRAM Sophie DesRosiers, Planétarium de Montréal Impact crater morphology: THEMIS Visible Image impact crater on Mars Central Peak (cp): visible in mostly large craters, the floor of the crater can rebound or get uplifted during the impact Wall (w): the steepest part, where loose debris can fall to the floor Floor (f): the bottom of the crater which can collect debris from the sides of the crater U S Rim (r): where rock is folded above original A / L P surface J SA/ A N Satellite View Ejecta (ej): material from inside the crater that gets thrown out during impact surface ej r w cp crust f MARS EDUCATION PROGRAM Side View of a Crater Where do we find craters on Mars? Hellas Planitia Mars Largest crater in solar system! MARS EDUCATION PROGRAM MOLA map 2,100 kilometer diameter NASA/JPL Craters unique to Mars: Rampart (“splosh”) craters Tooting Crater, Mars Lobate ejecta MARS EDUCATION PROGRAM Victoria Crater, Mars NASA/JPL NASA/JPL Endurance Crater, Mars Mars Exploration Rover Opportunity’s Landing site August 2004 MARS EDUCATION PROGRAM NASA/JPL NASA/JPL Craters are windows into a planet’s geologic past Craters expose rock layers for scientists to study THEMIS images NASA/JPL/ASU NASA/JPL/ASU HiRISE mosaic NASA's Mars Exploration Rover Opportunity examined the rim of Victoria Crater; note the layers of impact breccia (fragments thrown out MARS EDUCATION PROGRAM of crater during impact). NASA/JPL NASA/JPL-Caltech/Cornell/U.S. Geological Survey How are impact craters modified on Earth and Mars? Impact crater, Mars • Eroded (wind, water, tectonism, and volcanism) • Covered or filled in (water, vegetation, sediments, landslides, lava, and ejecta) Victoria Crater, Mars NASA/JPL Lonar Crater, India MARS EDUCATION PROGRAM Tiku Ravat MARS EDUCATION PROGRAM THEMIS 1N, 70E Wind streaks Martian craters: Modification by wind THEMIS 44N, 38.3E NASA/JPL/ASU Sand dunes (dark areas) ASU NASA/JPL/ THEMIS 19N, 284.9E Yardangs (ridges) NASA/JPL/ASU MARS EDUCATION PROGRAM THEMIS 43.6N, 296.4E Channels and deposition of sediments Martian craters: Modification by water sediments NASA/JPL/ASU THEMIS 16N, 329.6E Streamlined Islands NASA/JPL/ASU THEMIS 36.3N, 292.8E Gullies NASA/JPL/ASU MARS EDUCATION PROGRAM THEMIS 12.6N, 83.8E 12.6N, THEMIS Martian craters: Modification by Modification craters: Martian gravity Slumps (slumping and landslides) and (slumping NASA/JPL/ASU THEMIS 0N, 313.4E 0N, THEMIS rim crater Landslides NASA/JPL/ASU MARS EDUCATION PROGRAM THEMIS 0N, 0E THEMIS 0N, 1. Cross-cutting relationships feature cutisolderthan whatcutit.” Using cratersasdatingtools NASA/JPL/ASU THEMIS 29.7N, 1.7E THEMIS 29.7N, -“The -“The NASA/JPL/ASU 288E THEMIS -54N, 3 2 1 NASA/JPL/ASU Using craters as dating tools 2. Cratering rate - the more 70N craters there are on a surface, the older the surface. Which is surface is older? 0N U S A / L JP / A S A THEMIS 14.1N, 287.9E N U S A / L P J / MARS EDUCATION PROGRAM A S THEMIS 36.8N, 42.7E A N 70S 0E NASA/JPL MARS EDUCATION PROGRAM3. Crater modification modified a crater, the older it is. THEMIS 69.1N, 273.6E Using craters as dating tools NASA/JPL/ASU - generally, the more craters Which appear older? THEMIS 44N, 38.3E NASA/JPL/ASU Determining the age of a crater Well defined crater with little to no modification Preserved Partially modified crater, but floor, central peak, rim, walls, and ejecta are still visible Modified Mostly eroded or covered crater; MARS EDUCATION PROGRAM features difficult to see Destroyed NASA/JPL/ASU Are there meteorites on Mars? MARS EDUCATION PROGRAM NASA/JPL NASA/JPL Iron meteorite found on Mars! By Mars Exploration Rover Opportunity in January 2005 “Heat Shield Rock” NASA/JPL Impact craters help us understand: • The geologic history and age of a planet’s surface • How geologic processes work on different worlds, and • The importance of impacts in planetary formation and evolution MARS EDUCATION PROGRAM.