Lab6_Near Earth Asteroids

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Astronomy

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Oct 30, 2023

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LAB 6: NEAR EARTH ASTEROIDS 60pts. OBJECTIVES This laboratory is to examine information on Near Earth asteroids and possible collisions. SKILLS/COMPETENCIES  Interpret tables or graphs.  Present data by construction of charts and graphs.  Evaluate the relevancy of data. BACKGROUND ON NEOS AND NEAS Near-Earth Objects (NEOs) and Near Earth Asteroids (NEAs) are a special class of comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighborhood. Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system between the orbits of Mars and Jupiter. The scientific interest in comets and asteroids is due largely to their status as the relatively unchanged remnant debris from the solar system formation process some 4.6 billion years ago. The giant outer planets (Jupiter, Saturn, Uranus, and Neptune) formed from an agglomeration of billions of comets and the left over bits and pieces from this formation process are the comets we see today. Likewise, today's asteroids are the bits and pieces left over from the initial agglomeration of the inner planets that include Mercury, Venus, Earth, and Mars. As the primitive, leftover building blocks of the solar system formation process, comets and asteroids offer clues to the chemical mixture from which the planets formed some 4.6 billion years ago. If we wish to know the composition of the primordial mixture from which the planets formed, then we must determine the chemical constituents of the leftover debris from this formation process - the comets and asteroids. NASA's search program designed to discover 90% of the NEO population (1 km in diameter or larger) within 10 years is under way. The chart below shows the cumulative total known near-Earth asteroids versus time. NEA Lab 10 pages

NEA Lab 10 pages

LAB FIGURE 1: Near Earth asteroids up through 2005 The upper curve area shows all known near-Earth asteroids while the lower area shows only large near-Earth asteroids. In this context, "large" is defined as an asteroid having an absolute magnitude (H or brightness) of 18.0 or brighter which roughly corresponds to diameters of 1 km or larger. Programs (and year) that search for NEAs include: Lincoln Near-Earth Asteroid Research, LINEAR (1996) Near Earth Asteroid Tracking, NEAT (2001) Spacewatch (1984) Lowell Observatory Near-Earth Object Search , LONEOS (1993) Catalina Sky Surveys, CSS (2003) Japanese Spaceguard Association, JSGA (2000) Italy’s Asiago DLR Asteroid Survey, ADAS (2001) NEA Lab 10 pages

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TASK 1: INTERPRETING THE NEA GRAPH 1. (2) a. How many total asteroids were discovered by 2000? b. How many total asteroids were discovered by 2006? 2. (2) a. How many large asteroids were discovered by 2000? b. How many large asteroids were discovered by 2006? 3. (2) What was the average asteroid detection rate from 2000 to 2006 (for all NEA’s)? 4. (2) Assume that the detection rate stays the same. How many total asteroids will be discovered by 2010? 5. (2) a. As more and more of the larger NEAs are discovered, how do you think the shape of the bottom curve will change over to next 10 years? (2)b. The next 50 years? NEA Lab 10 pages

On the next page are the figures showing NEA detections as of June 2013. 6. (2) These graphs are presenting slightly different information than the graph of “Known Near Earth Asteroids” that you looked at before. Please explain the difference. 7. (2) What does Figure 1 show about the rate of discovery for all NEA’s from 2006 to 2013? 8. (2) What does Figure 2 show about the rate of discovery for large NEA’s from 2006 to 2013? 9. (1) Do these updated graphs support your conclusion for questions 5a and 5b? NEA Lab 10 pages

Figure 1: NEA’s discovered every 6 months (01/2012) Figure 2: large (>1 km) NEAS discovered every 6 months (01/2012) TASK 2: UNDERSTANDING IMPACT PROBABILITIES NEA Lab 10 pages

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From your textbook, we have Figure 3 that shows the likelihood of space debris impacting the Earth. FIGURE 3: "CURVE FROM TEXTBOOK" 10. (3) NASA is looking for asteroids one km or larger. a. What would the effects be of a one km asteroid striking the Earth? b. About how large would the crater be? c. What is the smallest-sized asteroid that could cause widespread devastation? 11. (2) a. According to Figure 3: "curve from textbook" On average, how often does a 1 km asteroid size strike the Earth? NEA Lab 10 pages

b. A 100 meter diameter asteroid? 12. (2) Based on the graph in figure 4 (the curve from the textbook), do you think the NASA NEO programs using a one km size search criteria is the right decision? Why or why not? 13. (2) Do you think Figure 3 might change as more asteroids are discovered? Why? TASK 3: INTERPRETING IMPACT DATA 14. (4) How do you think astronomers get their estimates of impact rates? (This is a question about what you think. All thoughtful, well-written answers will receive full credit.) One tool for making predictions about impact rates is to study impact events on Earth through astroblemes. An astrobleme is an impact crater (impact basin) is usually a circular depression on the surface of a body caused by a collision of a smaller body (meteorite, asteroid, comet) with the surface. In the center of craters on Earth a crater lake often accumulates, and a central island or peak caused by rebounding crustal rock after the impact is usually a prominent feature in the lake. NEA Lab 10 pages

15. (6) Fill in the data for the fourth column in the table below: Name Location Crater Diameter Estimated Impactor Size (crater diameter / 10) Age (years) Vredefort South Africa 300 km 2 billion+ Sudbury Canada 250 km 1.85 billion Chicxulub Mexico 170 km 65 million Popigai Russia 100 km 35.7 million Manicouagan Canada 100 km 214 million Acraman Australia 90 km 590 million Chesapeake Bay US 90 km 35.5 million Puchezh- Katunki Russia 80 km 167 million Morokweng South Africa 70 km 145 million Kara Russia 65 km 70 million Beaverhead US 60 km 600 million Tookoonooka Australia 55 km 128 million Charlevoix Canada 54 km 342 million Siljan Sweden 52 km 361 million Kara-Kul Tajikistan 52 km 5 million Montagnais Canada 45 km 50 million Araguainha Brazil 40 km 244 million Woodleigh Australia 40 km 364 million Mjølnir Norway 40 km 142 million Saint Martin Canada 40 km 220 million Carswell Canada 39 km 115 million Clearwater West Canada 36 km 290 million Manson US 35 km 73.8 million Yarrabubba Australia 30 km 2 billion Slate Islands Canada 30 km 450 million Shoemaker Australia 30 km 1.63 billion Keurusselkä Finland 30 km 1.8 billion Mistastin Canada 28 km 28 million Clearwater East Canada 26 km 290 million Nördlinger Ries Germany 25 km 14.8 million Steinheim crater Germany 3.8 km 15 million Gatun structure Panama 3.0 km 20 million Lonar Crater India 1.8 km 52,000 Meteor Crater US 1.2 km 49,000 NEA Lab 10 pages

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(Arizona) Odessa US 0.2 km 50,000 16. (6) Now, you’ll use the table of astrobleme data to make your own estimates about the frequency of impacts. a. Do you think that this is a complete record of impacts on Earth? Explain why or why not. b. Show all your work and/or explain your method for using the information from the table to calculate: how often we should expect to be hit by an object 9-10 km in diameter; how often we should expect to be hit by an object 4.5-5.5 km in diameter; and how often we should expect to be hit by an object 2.8-3.2 km in diameter. 17.(3) How do your estimates compare to the information from Figure 3: "curve from textbook"? Be specific and, if your estimates a different, explain why you think this might be. NEA Lab 10 pages

18.(3) Now go to https://cneos.jpl.nasa.gov/ Spend some time familiarizing yourself with this website and some of the terminology used for building tables of NEA’s. Check out the NEO Basics, Sentry and Asteroid Watch “Quick Links” on the menu on the left side of the page. Click on the NEO Groups link. What is the orbital criterion for an object receiving an NEO designation? What is the difference between an NEC and an NEA? What are the specific criteria for designating an object as a PHA? 19.(3) Now click on the Life on Earth link. What event occurred ~65mya? Briefly describe how this event created conditions responsible for the evolution of humans. 20.(5) Now return to the main menu and click on the Close Approaches link. Then click on the NEO link. Examine the table that’s automatically generated. Find the object with the lowest CA (Closest Approach) LD (Lunar Distance) value. Record its name, CA date and time, LD nominal and minimal distances, its velocity and size. Given the information in Figure 4 above, what would be the result of an impact if this object were to strike downtown Denver? Now find the largest object in the NEO table and record the same info as for the one above. How would the result of this object striking Denver be different? 21.(2) Now change the Table settings to Future Only and Nominal Distance <=1LD. Over the next 25 years find the object will have the closest approach to Earth and list the characteristics like you did question 20. What damage would this object likely to produce if it was to impact the downtown Denver area? NEA Lab 10 pages

NEA Lab 10 pages

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