Slide 1Menace from Outer Space
It is not an Empty Space!
NEOs shown in red. Main belt asteroids
shown in green. Comets shown in
blue.
Slide 2Menace from Outer Space
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.
Slide 3Menace from Outer Space
Preventable Menace
Comets:– Short Period– Long Period
Near Earth Objects (NEOs):– Meteoroids– Near Earth Asteroids (NEA), also known as
Minor Planets.
Slide 4Menace from Outer Space
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).
Slide 5Menace from Outer Space
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)
Slide 6Menace from Outer Space
Hale-Bopp in Maltese Skies
Discovered on July 23, 1995.
Closest approach to Earth, on March 22, 1997.
Period: 4200 – 2380 Years.
Slide 7Menace from Outer Space
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
Slide 8Menace from Outer Space
Slide 9Menace from Outer Space
Comet C/2001 Q4 (NEAT)
April 18, 2004 April 19, 2004
Slide 10Menace from Outer Space
Comets Bradfield and LINEAR Rising, April 25, 2004 in California
Slide 11Menace from Outer Space
Comet Bradfield is passing the Sun.Photo taken by NASA's sun- orbiting satellite SOHO.
Slide 12Menace from Outer Space
Comet Shoemaker-Levy 9
Image taken by HST in 27 Jan 1994 six months before the pieces crashed into Jupiter.
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.
Slide 13Menace from Outer Space
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.
Slide 14Menace from Outer Space
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!
Slide 15Menace from Outer Space
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.
Slide 16Menace from Outer Space
Main Asteroid Belt
Bode’s Law
Remains of a planet?
Slide 17Menace from Outer Space
Asteroid Gaspra
The first asteroid observed in a fly-by made by a spacecraft (Galileo) in October 1991.
20 x 12 x 11 km
Slide 18Menace from Outer Space
Asteroid Gaspra
Rotational periodof 7.04 hours
Slide 19Menace from Outer Space
Kleopatra Asteroid 216Kleopatra Asteroid 216 217 x 94 km Odd dumbbell shape
Slide 20Menace from Outer Space
EROS Asteroid 433EROS Asteroid 433
14 x 14 x 40 km
Visited by NEAR spacecraft in Feb. 1999.
Slide 21Menace from Outer Space
Orbit of Asteroid Eros: Amos Type Asteroid
Slide 22Menace from Outer Space
Diameterof Asteroid
Kinetic EnergyArea 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
Collision Probability and Anticipated Damage
Slide 23Menace from Outer Space
Slide 24Menace from Outer Space
Earth Sterilizing Impact
Mass Extinction ImpactCivilization Threatening Impact
Slide 25Menace from Outer Space
Barringer Crater, Arizona, USA
Diameter: 1.2 Km Age: 50,000 Yr. Caused by a 3.5
MT Impact
Slide 26Menace from Outer Space
Amguid Crater,Algeria
Diameter: 450 m Age: < 100,000 Yr.
Slide 27Menace from Outer Space
Morasko Craters, PolandAge: 10,000 Yr.Size: < 100 m
Slide 28Menace from Outer Space
Recognized Impact
Craters in Africa
Slide 29Menace from Outer Space
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.
Slide 30Menace from Outer Space
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.
Slide 31Menace from Outer Space
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
Slide 32Menace from Outer Space
Slide 33Menace from Outer Space
Adapted from“State of the Planet” By SirDavid AttenboroughA BBC Production
Slide 34Menace from Outer Space
Slide 35Menace from Outer Space
Chicxulub Crater,Yucatan, Mexico
Adriana Ocampo
Diameter: 170 Km Age: 65 M Yr. 100 Million MT
Slide 36Menace from Outer Space
K-T Boundary
Raton Basin, Colorado,
USA
Slide 37Menace from Outer Space
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
Slide 38Menace from Outer Space
Tunguska Map
Go back
Slide 39Menace from Outer Space
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.
Slide 40Menace from Outer Space
PeekskillVideo Clip
Slide 41Menace from Outer Space
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.
Slide 42Menace from Outer Space
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.
Slide 43Menace from Outer Space
Detection, Cataloging, and Tracking Projects
LINEAR (Lincoln Near Earth Asteroid Research)
– Started in 1996.– MIT/ NASA/ USAF.– Located Boston,
Massachusetts.LINEAR NEO Search Systems
Slide 44Menace from Outer Space
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.
Slide 45Menace from Outer Space
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).
Slide 46Menace from Outer Space
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.
Slide 47Menace from Outer Space
Giotto– July 1985 – July 1992.– ESA– Studied comet Halley.
NEAR (Near Earth Asteroid Rendezvous).
– Feb. 1996 – Feb. 1999– NASA– Mission to:
• Comet Hyakutake.
• Asteroid 253 Mathilde.
• Asteroid 433 Eros.
NEAR
Space Missions to Comets and Asteroids
Slide 48Menace from Outer Space
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.
Slide 49Menace from Outer Space
Questions
Slide 50Menace from Outer Space
Orbits: No Straight Lines in SpaceLaunch Point
UNBOUNDHigh speedHyperbolic Orbit
Parabolic OrbitBarely Escapes:Escape Velocity
BOUND – Medium Speed Elliptical Orbit
BOUNDCircular Orbit
BOUND – Low SpeedElliptical Orbits
Sun
Escape Velocity =
1.4 x Circular Velocity
BOUND – High Speed Elliptical Orbit
Slide 51Menace from Outer Space
Orbital Elements
Eccentricity of orbit = e = c/2a0 ≤ e < 1e = 0 for a perfect circle (foci overlap)e → 1 as b → 0
Semi minor axis
Slightly eccentric
orbit
Highly eccentric orbit
aSemi major
axis
b
cDistance between foci
SunVacant focus
Orbiter
Semi-major axis (a) Periapsis distance = a (1 - e) Apoapsis distance = a (1+ e) Semi-minor axis (b) = a √(1 - e²)
Period Epoch Inclination to
the Ecliptic
Slide 52Menace from Outer Space
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
34
5
6
(Sun or Planet)
PC
A
(Periap
sis)
(Ap
oap
sis)
Retrograde elliptical orbit
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