Impact Crater Lab

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Anne Arundel Community College *

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Geology

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Oct 30, 2023

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Modeling Impact Craters P REPARATION Before beginning this lab,  Read Tarbuck et al. (2015) Chapter 22 pp 667 to 668, and Sections 22.2 & 22.5  Read Class 12 Plate Tectonics and Impact Craters (Online in the Canvas Content for Module 2 Week 6.)  Optional: Read the introduction to impact craters: at https://pubs.er.usgs.gov/publication/70168934  Read the Introduction to the Lab section below.  Take the Pre-Lab Quiz on Canvas before the class for which this lab is to be performed. L EARNING O BJECTIVES The activities in today’s lab are geared toward the following competencies and learning objectives: Compare processes that change Earth’s crust to those on other planets, within our solar system and beyond Learning Objectives: d. Explain the factors affecting the appearance of impact craters and ejecta e. Compare processes on Earth to those on other planets Competency 5: Identify the processes involved in learning Learning Objectives: a. Identify current understandings and/or long-held beliefs that are incorrect. b. Revise beliefs based on the results of experiments. c. Make connections between lecture and lab experiments. d. Participate in a community of learners. I NTRODUCTION A number of planetary probes, both those sent out to look (the Mariner and Voyager series) and the stunning observations made from Earth, have caused us to realize that Solar System objects other than the Moon are substantially cratered. Craters can shed light on the history of the Solar System, even though most craters on Earth have long eroded away or been destroyed by tectonic plate activity, or were never created on the gas and ice giants, bodies without solid surfaces Tremendous energies are involved to produce a crater on a planetary surface. For the Moon, most of the craters visible in a modest telescope were produced by masses of thousands to millions of kilograms hitting the surface with speeds of up to 70 kilometers per second! The energy released upon impact is so great that any known substance would be disintegrated into

atoms, and vaporized to a large extent. (See the Astronomy Workshop website http://janus.astro.umd.edu/astro/impact/ for specific examples.) The kinetic energy (KE) released is measured in terms of kinetic energy, calculated as ½ mass times velocity squared, or ½ mv2. KE=1/2*m*v 2. Where: KE (Joules), m (kg), and v (meters/second) Notice that, as the mass of the impactor increases, so does the KE released. And, if the velocity of the impactor increases, the KE goes up as the square of the velocity. For example, the Barringer Crater impactor in Arizona is estimated to have had a mass of 10 billion kg (10,000,000 tons), coming in at a speed of 36,000 km/hr, (22,370 miles/hr) which released about 4 x 10 16 Joules of energy. This is ten times the energy of the USA’s most powerful nuclear weapon (Wikipedia, 2013). Since it is unwise (and expensive!) to shoot objects with the mass of a mountain at high speeds in our lab, we must make a model of an impact with more modest masses and speeds. We want to minimize resistance in the material used for the “meteoroid” and “surface”, so the material used should have a very low tensile strength – like wheat flour. A “meteoroid” of flour falling from a height onto a “surface” of flour can provide a nice approximation to an impact crater. It’s more important that you make and report careful, well-documented observations rather than get the “right” answer. You are expected to provide complete and accurate descriptions of the conditions and results of the various tests made during this lab. Part 1. Flour Crater Experiment See the ‘Crater Impact Example’ PowerPoint for examples of videos. EXPERIMENTAL SETUP This lab has been modified to be set up and performed at home using materials that can be found in the kitchen and/or obtained from the grocery store for reasonable prices. (The material not used in the lab can be used for preparing meals or the like.) Consider, potentially, that your students will be repeating this same lab at home for you. Do not wash flour down your sink drain, throw the powder into a waste receptacle. Obtain: 1. the crater container- an unbreakable plate or bucket (put a towel on the table or floor under the crater container to catch the spill over) 2. sand—1 cup (optional- use only if flour is not available) 3. flour-- about 2 to 3 cups 4. two small meteorites or small rocks around 1-inch x 1-inch diameter or 0.5 x 1-inch (approximate).

Methodology. Place the flour in the center of the bowl and use your fingers in a raking motion to create as steep a cone as possible. DO NOT PACK. Maximize the angle of repose for the mixture. It is important to have steep sides to allow the meteorite to inflict as much damage as possible- after-all it makes for a good movie. Using Figure 1 as a guide, locate your phone on the outside edge of the crater container for a closeup view of the impact site (it can be in the bowl as well- position for the best close-up) Practice a few impacts with a meteorite to establish the technique and method that you need to coordinate the video and meteorite release. Rebuild the cone each time you practice so that the cone is as steep as it can be when you take to video. Do not pack the surface unless you intend to make it part of your experimental conditions. Record in SLOW MOTION. Figure 1. Impact Crater Equipment Arrangement Procedure Record the height on the meter stick that will be your ‘atmosphere reentry point’. Produce 2 SLOW MOTION videos (5 to 10 seconds long) one for each meteor size that demonstrate the impact of the meteorites on the impact cone. One video will use the large meteorite and the second video will use the small meteorite. The meter stick provides a launching point for both meteorites so that the results are comparable. Do not add any extra speed to the meteorite launch, as that will invalidate the comparison of the two meteorites. Repeat the impacts until two really good impacts are recorded. Rebuild the impact cone for each attempt. Do not pack the surface of the material. Take an overhead photo of the pre-impact mound and a final photo of the post impact area for each meteorite. Drop Elevation Meter Stick A Meteor Path Camera Bucket/Plate B Field of view Impact Point

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Questions Diagrams 1 and 2. Profile and Topography for each meteorite. Use the diagram as a guide to draw your full-page results for each meteorite. Insert the photographs at low transparency as a backdrop to draw upon to identify the profile and topography. Use the ‘Crater Impact Example’ PowerPoint for guidance. Use this Topological Review for more information , use this info to create your own contour map for your impact area. Use centimeters as your elevation units. Diagram 1. Before Impact Show the location of impact and identify the debris fields Diagram 2. After Impact 1. Describe the large meteorite and the small meteorite 2. Describe the large impact crater a. a. Dimension 2.25in x 2in b. Depth of impact 1.25in c. Spread of material (ejecta or debris) 26in d. Was the meteor buried or exposed at the impact site? Exposed 3. Describe the small impact crater a. Dimension 1.5in x 1in b. Depth of impact 2in c. Spread of material (ejecta or debris) 7in d. Was the meteor buried or exposed at the impact site? Buried 4. Compare the two impact craters for shape and other curiosities using profiles and topographies While both meteorites created impact craters the craters themselves were very different. The small meteorite created a small deep whole but didn’t have too much ejecta. The large meteorite had a much bigger impact. This meteorite basically leveled the mountain that was once there. The crater itself ended up being shallow but wide and the ejecta spread much farter al the way around the impact site. 5. Sketch a picture of your crater on paper and insert the .png or .jpeg file in your word document. Profile before Topography Rul er Rul er Profile after Debris Field Impact Debris Field Size Small Large Shape Almost spherical oval Weight (g) 5.7 45 Material Rock Rock

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Part 2. Out of this World Craters The major check on a scientific theory is to compare its predictions to observations of the phenomenon under investigation. Carefully study the maps of the respective planet or moon and use a tabular format to list areas of agreement and disagreement with the model craters produced in this lab. PLANET (updated 7/12/21) POINTS OF AGREEMENT POINTS OF DISAGREEMENT MERCURY http://www.space.com/18040-mercury- craters-cookie-monster-photo.html (Moskowitz, 2012) -impact ridge -no central peak -no rays -no impact basin -multiple impacts -minimal ejecta MOON (LUNA) https://apod.nasa.gov/apod/ap180507.html (NASA 2018) -rays -impact ridges -ejecta -central peaks -depth of impact MARS https://www.jpl.nasa.gov/news/nasa-mars- orbiter-examines-dramatic-new-crater (NASA JPL) -rays -small size -ejecta -impact ridges -central peak -very large spread out rays EUROPA http://www.lpi.usra.edu/resources/europa/thic kice/ Use the second, compound image (Comparison of impact crater…). (LPI ) -impact ridges -ejecta -multiple rings -central peak Points of agreemen t contain descriptions of craters similar to this lab, i.e., impact ridge, ejecta blanket, diameter, and so on. Points of disagreement contain descriptions of craters not aligned with this lab, i.e., tidal crust, blast zones and so on. Some differences may be the result of our limited scope. Question 1 : Do real craters show any specific features that were not seen in your experiments? The real craters sometimes seemed to have multiple rings from impact and the material ofe meteorite sometimes collapses on itself creating central peaks. Question 2 : Can you find any examples of the features you produced in your model experiments on real planets? Include specifics about which features and which planet or moon. This crater reminds me of the crater created by my large meteorite. It is Sunset Crater Volcano in Arizona on Earth. It looks similar to me because it looks like it landed on some kind of mountain and severely leveled out the mountain leaving high ridges but a shallow basin. Question 3 : Describe how you would change this lab to make it more realistic or interesting. I would say maybe instead of a steep hill almost creating a taller flatter shape to see how the crater effects a flatter surface while still having room to create a crater with depth.

Acknowledgement Beth Hufnagel adapted this lab from the “Modeling Impact Craters” lab developed by Leslie J. Tomley, San Jose State University ( ljtomley@email.sjsu.edu ). Further revisions were made by J. Kline and K. Koester (Feb 2007), J. Barbour (Jan 2012) and P. Hill (Oct 2020) References Jet Propulsion Laboratory (JPL) (2012). A Spectacular New Martian Impact Crater. Retrieved February 23, 2014 from http://www.jpl.nasa.gov/spaceimages/details.php ? id=PIA17932 Lunar and Planetary Institute (LPI) (n.d.). New Measurements of Impact Crater Topography Show that Europa has a Thick Ice Shell: Comparison of impact crater morphology on Ganymede and Callisto (top row) and on Europa (bottom row). Retrieved February 23, 2014 from http://www.lpi.usra.edu/resources/europa/thickice/ Moskowitz, C. (2012). Mercury Craters look like Cookie Monster in NASA Photo. Retrieved February 23, 2014 from http://www.space.com/18040-mercury-craters-cookie- monster- photo.html NASA Near Earth Object Program (1969). Impact Crater Chain on Moon Apollo 11. Retrieved February 23, 2014 from http://neo.jpl.nasa.gov/images/moonchain.jp g. Wikipedia (2013). B83 Nuclear Bomb. Retrieved October 14, 2013 from http://en.wikipedia.org/wiki/B83_nuclear_bomb Space.com (2020) Retrieved Oct 2, 2020 from https://www.space.com/41696-moon- crater-moretus-amazing-photo.html

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