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