The document discusses the potential threats posed by Near-Earth Objects (NEOs) such as asteroids and comets, detailing their orbits, the impact risks they present, and historical mass extinctions linked to such events. It emphasizes the importance of tracking these objects to prevent catastrophic collisions with Earth and outlines past space missions aimed at studying them. Additionally, it highlights the need for continued research and preventive measures to mitigate potential impacts in the future.

1. It is not an Empty Space! NEOs shown in red. Main belt asteroids shown in green. Comets shown in blue.

2. Doomsday Scenario Triggered by a burst of gamma rays from a nearby exploding star (supernova). No possible defense nor remedies. Might be the cause of the Ordovician extinction. It can happen again any time.

3. Preventable Menace Comets: Short Period Long Period Near Earth Objects (NEOs): Meteoroids Near Earth Asteroids (NEA), also known as Minor Planets.

4. Comets Highly eccentric orbits with big inclination angles with the Ecliptic plane. Short-period: Comet Halley: Last visit (1986), 76 years period. Long-period comets: Hyakutake: Last visit (1996), previous (17,500 years ago), next (in 29,500 years). Hale-Bopp: Last visit (1997), previous (4,200 years ago), next (in 2380 years).

5. Comet Recipe The "ingredients" for a six-inch comet are: 2 cups of water 2 cups dry ice (frozen carbon dioxide) 2 spoonfuls of sand or dirt a dash of ammonia a dash of organic material like dark corn syrup ( Gulepp tal Harrub works fine)

6. Hale-Bopp in Maltese Skies Discovered on July 23, 1995. Closest approach to Earth, on March 22, 1997. Period: 4200 – 2380 Years.

7. Seeds of Life Theory No life without Liquid water. Comets contain plenty of ice and organic material. Impact energy is enough to melt ice into pools of hot water. Fossils of hot-water bacteria are the oldest on Earth (3.8 billion years). Comets might be the source of these oldest baths of life. Bacteria in a hot-water spring

9. Comet C/2001 Q4 (NEAT) April 18, 2004 April 19, 2004

10. Comets Bradfield and LINEAR Rising, April 25, 2004 in California

11. Comet Bradfield is passing the Sun. Photo taken by NASA's sun- orbiting satellite SOHO.

12. Comet Shoemaker-Levy 9 Discovered in March 1993. Torn into 21 pieces when it passed within 25,000 Km of Jupiter's cloud tops on July 8, 1992. Captured into orbit around Jupiter. Collided with Jupiter after two years in July 1994. Image taken by HST in 27 Jan 1994 six months before the pieces crashed into Jupiter.

13. Meteors Meteoroid Every day, Earth scoops up thousands of tons of space rock and dust (meteoroids) while going on in its orbit around Sun. Meteor A meteor is the luminous phenomenon seen when a meteoroid enters the atmosphere, commonly known as a shooting star. Meteorite A part of a meteoroid that survives through the Earth's atmosphere and reaches ground.

14. Meteorite: A Chip of Asteroid Vesta Fell in Western Australia in 1960. It has the same pyroxene signature as of Vesta. Vesta has a diameter of 525 km and is the brightest of all asteroids!

15. Near Earth Asteroids (NEAs) Amors, Apollos, and Atens. They range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles. More than 2000 Potentially Hazardous Asteroids (PHAs) larger than 1 Km in diameter. Sixteen asteroids have a diameter of 240 km or greater.

16. Main Asteroid Belt Bode’s Law Remains of a planet?

17. Asteroid Gaspra The first asteroid observed in a fly-by made by a spacecraft (Galileo) in October 1991. 20 x 12 x 11 km

18. Asteroid Gaspra Rotational period of 7.04 hours

19. Kleopatra Asteroid 216 217 x 94 km Odd dumbbell shape

20. EROS Asteroid 433 14 x 14 x 40 km Visited by NEAR spacecraft in Feb. 1999.

21. Orbit of Asteroid Eros: Amos Type Asteroid

22. Collision Probability and Anticipated Damage Diameter of Asteroid Kinetic Energy Area Devastated Average Interval (Years) Death Toll (Meter) MT of TNT (Nucl. Bombs) Sq. Km Earth Person 50 10 (500 bombs) 1900 100 yr 1 million 100 75 (3,750 bombs) 7200 1000 yr 3 million 200 600 (30,000 bombs) 29,000 5000 yr 14 million 500 10,000 (0.5 million bombs) 70,000 40,000 yr 30 million 1000 75,000 (3.75 million bombs) 200,000 100,000 yr 60 million 2000 1 million (50 million bombs) undefined 1 million yr >1.5 billion All 90 yr

24. Earth Sterilizing Impact Mass Extinction Impact Civilization Threatening Impact

25. Barringer Crater, Arizona, USA Diameter: 1.2 Km Age: 50,000 Yr. Caused by a 3.5 MT Impact

26. Amguid Crater, Algeria Diameter: 450 m Age: < 100,000 Yr.

27. Morasko Craters, Poland Age: 10,000 Yr. Size: < 100 m

28. Recognized Impact Craters in Africa

29. Mass Extinction Mass extinctions resulted from drastic environmental changes that followed events such as asteroid or comet impacts or massive volcanic eruptions. They caused life loss on earth for up to 95% of all species.

30. The Five Worst Mass Extinctions Cambrian Extinction 500 million years ago. Causes unknown. Changes in sea level. Ordovician Extinction 439 million years ago. Glaciers formed. Drop in sea levels. Attributed to a supernova. Devonian Extinction 364 million years ago. Cause unknown. 70% of all species vanished. Permian Extinction 245 million years ago. Worst mass extinction. 96% of all species vanished. Attributed to volcanic activity. Cretaceous-Tertiary (KT) Extinction 65 million years ago. 70% of all species including the dinosaurs were wiped out. Attributed to a collision with a comet or an asteroid.

31. Geologic Timescale Era Period Epoch Approximate duration (millions of years) Approximate number of years ago (millions of years) Cenozoic Quaternary Holocene 10,000 years ago to the present Pleistocene 2 .01 Tertiary Pliocene 11 2 Miocene 12 13 Oligocene 11 25 Eocene 22 36 Paleocene 7 58 Mesozoic Cretaceous 71 65 Jurassic 54 136 Triassic 35 190 Paleozoic Permian 55 225 Carboniferous 65 280 Devonian 60 345 Silurian 20 405 Ordovician 75 425 Cambrian 100 500 Precambrian 3,380 600

33. Adapted from “State of the Planet” By Sir David Attenborough A BBC Production

35. Chicxulub Crater, Yucatan, Mexico Adriana Ocampo Diameter: 170 Km Age: 65 M Yr. 100 Million MT

36. K-T Boundary Raton Basin, Colorado, USA

37. Tunguska Event A cataclysmic explosion caused by an estimated 15 - 40 MT impact. Took place at 7:17 in the morning on June 30, 1908. Location: Tunguska, Taiga of Siberia, Russia. People heard the explosion from 800 Km away. The blast was more than 1000 times the atomic explosion produced in Hiroshima in 1945. First time in history to observe a mushroom cloud explosion. Could be attributed to a collision by a fragment of Comet Encke. Explosion probably took place 8 Km above surface as no crater was found. Photos taken later in 1927 Map Continue

38. Tunguska Map Go back

39. Peekskill Meteorite 12.5 Kg chondrite meteorite Hit the back of Ms. Michelle Knapp's parked car on the evening of October 9, 1992, in Peekskill city, NY. Videotaped by people attending a football game. Fireball tracks from eastern Kentucky to New York City.

40. Peekskill Video Clip

41. Why Do We Study Comets and NEOs? Early discovery of their exact orbits is the key point in protection against collisions with them. Provide important information about the origins of the solar system, and life on Earth. They contain valuable resources that can be relied upon in future colonization of the nearby planets.

42. Preventive Actions Early discovery of potential impactors is the key point. All what we need is six minutes to escape a certain collision. It is difficult to destroy objects of diameter more than 1 Km. Nuclear explosions in space would be used to change the speed of such objects by few cm/s, causing a change in orbit enough to send them away from Earth.

43. Detection, Cataloging, and Tracking Projects LINEAR (Lincoln Near Earth Asteroid Research) Started in 1996. MIT/ NASA/ USAF. Located Boston, Massachusetts. LINEAR NEO Search Systems

44. NEAT (Near Earth Asteroid Tracking) Started in 1995. JPL/ NASA/ USAF. Located in Hawaii. Detection, Cataloging, and Tracking Projects Discoveries are: Reported to the IAU’s Minor Planet Center (MPC). Published on NEOCP web site.

45. Flarestar Observatory, Malta Observatory Code:171. Conducting asteroid observations for the IAU Minor Planet Center (MPC). Rotation period of several asteroids has been discovered. Meade 250 mm. Schmidt-Cassegrain telescope ( CCD imaging).

46. Space Missions to Comets and Asteroids Deep Impact Launched in Jan 2004. UMD/ JPL/ NASA. Mission is to impact comet Tempel 1 in July of 2005. Stardust Launched in February 1999. Collected dust from comet Wild 2. Scheduled to return in 2006. Rosetta Launched in March 2004. ESA 10 years trip to comet Churyumov- Gerasimenko Dawn Scheduled for launch in 2006. UCLA/ JPL/ NASA. Mission to asteroids Ceres and Vesta.

47. Giotto July 1985 – July 1992. ESA Studied comet Halley. Space Missions to Comets and Asteroids NEAR (Near Earth Asteroid Rendezvous). Feb. 1996 – Feb. 1999 NASA Mission to: Comet Hyakutake. Asteroid 253 Mathilde. Asteroid 433 Eros. NEAR

48. Conclusion Cosmic impacts represent an extreme example of the class of hazards with low probability but high consequences. Unlike other natural hazards, impacts can kill billions of people and endanger the survival of civilization. Unlike other natural catastrophes, large impacts can, in principle, be avoided by deflection to alter the orbit of the projectile. The initial step in any mitigation scheme is to survey the near-Earth asteroids and determine their orbits. Everyone of us is urged to provide support at any level to such efforts. Contact your local astronomical society for more information.

49. Questions

50. Orbits: No Straight Lines in Space Launch Point UNBOUND High speed Hyperbolic Orbit Parabolic Orbit Barely Escapes: Escape Velocity BOUND – Medium Speed Elliptical Orbit BOUND Circular Orbit BOUND – Low Speed Elliptical Orbits Sun Escape Velocity = 1.4 x Circular Velocity BOUND – High Speed Elliptical Orbit

51. Orbital Elements Eccentricity of orbit = e = c/2a 0 ≤ e < 1 e = 0 for a perfect circle (foci overlap) e -> 1 as b -> 0 Semi minor axis a Semi major axis b c Distance between foci Sun Vacant focus Orbiter Semi-major axis (a) Periapsis distance = a (1 - e) Apoapsis distance = a (1+ e) Semi-minor axis (b) = a √ (1 - e ²) Period Epoch Inclination to the Ecliptic Slightly eccentric orbit Highly eccentric orbit

52. The orbiter takes the same time to travel between each pair of points of the same color. It is slow between 1 & 2 because it is far from the central body. It is faster between 3 & 4 because it is closer to the central body. It reaches its fastest speed between 5 & 6 (exactly at P) where it is closest to the central body. It sweeps equal areas in equal intervals of time, i.e. the areas of the three sectors C-1-2, C-3-4, and C-5-6 are equal. 1 2 3 4 5 6 (Sun or Planet) P C A (Periapsis) (Apoapsis) Retrograde elliptical orbit