Asteroids attack the Earth – myth, speculation, or real danger?

1. Asteroids attack the Earth – myth, speculation, or real danger? Ruslana Glazman, Sharet school/ASTROTOP, Netanya, Israel

2. Main questions in the project: • How do we find asteroids in the sky? • How do we estimate the orbit of discovered asteroids? • What are asteroids and comets, and what is the difference between them? • Where do asteroids live? Do they live in the same area as comets? How do they arrive here? • What is the probability that an asteroid impact will cause a disaster in the very near future? Is the probability different depending on the amplitude of the catastrophe (affecting a region, country, or the whole planet)? • When was the last accident caused by asteroid or comet?

3. Asteroids: How to find asteroids in the sky?Data sources. • Method - permanent survey of a sky region by numerous groups in the world: NEO – Near Earth Objects search. • Sources of my observational matter: Eudoxos Obs., Cephalonia, Greece: D-Space network of robotic telescope (1) ; Wise Obs., Mitspe Ramon, Israel, with David Polischuk (2) (1) (2)

4. Asteroids: How do we find asteroids in the sky?Data analysis and identification of objects. EUDOXUS (D-Space) – Asteroid 2017 Mitspe Ramon – NEO search ( 3 clicks)

5. How do we estimate the orbit of discovered asteroids or comets? • Orbit is an ellipse • Parameters: a, b, i, ω,  • Eccentricity: • Aphelion = farthest distance = Ra, • Perihelion = nearest distance = q = Rp • Observing the asteroid over time in several positions gives the parameters of its orbit: 3 2 1 4 a b i ω Ω Ra α1,δ1,t1 α2,δ2,t2 α3,δ3,t3 ……….. αn,δn,tn

6. What are asteroids and comets, and what are differences between them? • Asteroids are stones (up to 1000 km). Asteroids have no tails. Meteorites are asteroids, falling to Earth. Their chemical contents are carbonaceous chondrite (~93%),iron (4%). • Comets are lumps of ice and frozen snow, covered by dark dirty spots of dust. The dark spots heat up when near the Sun, eject gas and dust, and form tails (two tails of dust and gas, separated by the pressure of solar wind)

7. Where do asteroids live? Do they live in the same area as comets? • We studied thedistribution of all asteroids and comets by distance (a) , inclination to ecliptic (i), and eccentricity (ε) (source:http://ssd.jpl.nasa.gov/?sb_elem, “Small-Body Orbital Elements”, catalog of Jet Propulsion Laboratory, NASA & CALTECH) Examples: AsteroidsComets

8. Where do asteroids live? Do they live in the same area as comets? Conclusions: • Orbitsofasteroids are localized in belts. Main belt - between Mars and Jupiter in interval between 2 AU and3.5 AU. Secondary narrow belt is on Jupiter’s radius 5 AU – “Jupiter Trojans”. Scattered external belt is on the same distance as Pluto (Kuiper belt) – is Pluto one of them? • The asteroid orbits in the main belt are near ecliptic plane with low inclination (i<30) and are circle-like (low eccentricity). • The main belt is fragmented on its inner side and splits (possible result of resonance with gravitational disturbances of planets and proper instability of the asteroid’s belt). • Inner asteroids (Near Earth) are rare and are scattered randomly in space from Venus to the Main belt (where they are ejected from the Main Belt as a result of collisions). • Comet’s orbits are divided in two groups: • External comets up to thousands AU with high eccentricity and high inclination (“hedgehog” distribution) – “Oort cloud” • Inner comets with perihelion > 4 AU with low eccentricity and inclination (“disc” distribution) like the asteroids These locations originate from a sequence of different stages in the Solar System’s origin from a primary gas-dust cloud to its present state

9. Location of planets and asteroids and the law of Titius- Bode • The law of Titius Bode explains the range of distances between the Sun and the planets: • Explanation – resonance orbits, stable opposite to gravitational disturbances • N=- – Mercury, N=1 – Venus, N=2 – Earth • N=3 – Mars, N=5 –Jupiter, N=6 – Saturn • N=7 – Uranus, N=8 – Pluto, N=9 – Sedna • Main Asteroid Belt is in position n=4 exactly. • What is it – remnant from former planet’s explosion (Phaeton) or primary blocks for future planet building? • Now, astronomers reject Phaeton’s hypothesis (deficit summary mass, chemical content of meteorites, Jupiter influence). • Answer – asteroids and comets are “junk” of primary matter, remained after construction of the solar system.

10. What is the probability to have a disaster from asteroid impact in the near future? • Data for analysis comes from craters from past impacts. Source of data: database of asteroid craters identified on Earth: http://www.unb.ca/passc/ImpactDatabase/CIDiameterSort2.htm

11. Asteroid impact and its sequences • Velocity of asteroid in collision– 10-20 km/sec • Energy of explosion comes from the kinetic energy of a stopped asteroid = mV2/2. Correspondent energy of explosion convert to: • Heating and evaporation of the asteroid/comet matter (chondrites / ice) • Emission of overheated gas • Shock wave and mass ejection into atmosphere and space • Plastic deformation of the Earth matter with earth quakes and strong seismic waves

12. Distribution of impact craters by amplitude and ages Planetary Catastrophe events (craters about 100 km - disaster region 10,000 km) Power: Million Megaton TNT The largest crater - 800 km, 3 million years - Africa. Another example- 300 km, 65 million years, Chicxulub, Mexico - Dinosaur’s killer (?) The last event - million years ago – Sweden – 130 km Mean time interval – 50-100 million years Regional Catastrophe events (craters about 10 km, disaster region 100-1000 km) Power: Million Megaton TNT The last event – 13,000 years ago – Iraq Mean time interval –1-3 million years Local Catastrophe events (craters 100 m - 1 km, disaster regions - ten kilometers) Power: 100-1000 Megaton TNT The last event – 100 years ago – Siberia, Tunguska (atmospheric explosion with disaster region - 40 km) Mean time interval - about thousands years

13. Conclusions • Asteroids and comets are stone and ice remnants of building junk from the period of the solar system construction. • They are situated in belts and clouds. • A small part of them were scattered from their belt as a result of a collision with another one and entered Earth orbit. • A small part of these guests has the probability to collide with the Earth. • Possible impact may be from Planetary catastrophe (one in tens millions of years), regional catastrophe (one in a few millions of years, and local catastrophe (one in a thousand – tens thousands of years) • Last local event was in 1908 in empty region in the East Siberia, “Tunguska”. Region of destruction – 40 km. Now more then 30,000 people live in this region (!). Where can we find a place for the next impact with minimum negative sequences? • Asteroid attack is real source of danger for a period of thousand years.

14. Who is waited to be the next visitor? • NEO – Near Earth Objects program = permanent monitoring of the all sky by network of telescopes for timely discovery and identification of potentially dangerous asteroids/comets • Apophis= 2004 MN4:size 400 m, disasters region = 100 kilometers, expected probability of impact = 1/1000 years It was discovered June 19, 2004 as a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a large probability that it would strike the Earth in 2029 (3%) = class 4 in Torino Scale of Impact hazards. Later (2006) orbit was calculated more exactly and possibility of impact in this transition was excluded (minimal distance about 30,000 km = just below the altitude of geosynchronous satellites (!!!), but without capture. • Data of the next transition is April 13, 2029, Apophis will be observed by naked eye. • Gravitational disturbances of Apophis orbit during transition near the Earth may shift it in new orbit with high probability of the impact. Next transition in 2036 may be dangerous. Apophis in Mitspe Ramon observation [David Polischuk (2004)] ? ?

15. One from the possible scenarios of impact catastrophe from “Deep Impact” (God forbid !!!)