menace from outer space

Menace from Outer Space

It is not an Empty Space!

NEOs shown in red. Main belt asteroids

shown in green. Comets shown in

blue.


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.


Preventable Menace

Comets:– Short Period– Long Period

Near Earth Objects (NEOs):– Meteoroids– Near Earth Asteroids (NEA), also known as

Minor Planets.


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).


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)


Hale-Bopp in Maltese Skies

Discovered on July 23, 1995.

Closest approach to Earth, on March 22, 1997.

Period: 4200 – 2380 Years.


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


Comet C/2001 Q4 (NEAT)

April 18, 2004 April 19, 2004


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


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


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.


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.


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!


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.


Main Asteroid Belt

Bode’s Law

Remains of a planet?


Asteroid Gaspra

The first asteroid observed in a fly-by made by a spacecraft (Galileo) in October 1991.

20 x 12 x 11 km


Asteroid Gaspra

Rotational periodof 7.04 hours


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


EROS Asteroid 433EROS Asteroid 433

14 x 14 x 40 km

Visited by NEAR spacecraft in Feb. 1999.


Orbit of Asteroid Eros: Amos Type Asteroid


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


Earth Sterilizing Impact

Mass Extinction ImpactCivilization Threatening Impact


Barringer Crater, Arizona, USA

Diameter: 1.2 Km Age: 50,000 Yr. Caused by a 3.5

MT Impact


Amguid Crater,Algeria

Diameter: 450 m Age: < 100,000 Yr.


Morasko Craters, PolandAge: 10,000 Yr.Size: < 100 m


Recognized Impact

Craters in Africa


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.


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.


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


Adapted from“State of the Planet” By SirDavid AttenboroughA BBC Production


Chicxulub Crater,Yucatan, Mexico

Adriana Ocampo

Diameter: 170 Km Age: 65 M Yr. 100 Million MT


K-T Boundary

Raton Basin, Colorado,

USA


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


Tunguska Map

Go back


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.


PeekskillVideo Clip


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.


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.


Detection, Cataloging, and Tracking Projects

LINEAR (Lincoln Near Earth Asteroid Research)

– Started in 1996.– MIT/ NASA/ USAF.– Located Boston,

Massachusetts.LINEAR NEO Search Systems


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.


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).


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.


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


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.


Questions


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


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


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

menace from outer space

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