Welcometo

SPACE

The inner solar

system (1900)

The inner solar

system (2000)

Near Earth Objects

Comets, Asteroids,

and Meteors

Comets• Icy bodies that orbit the sun• Comes from the Kuiper belt or

the Oort cloud• Composed of ice, frozen gases

(ammonia, methane, and CO2), and other organic compounds

The Oort Cloud• Discovered in 1950 Jan Oort, beyond Pluto

Kuiper Belt• Similar to Asteroid belt but found beyond

neptune.

Oort Cloud

Kuiper Belt

Comets• Diameter ranges from 1-10 km• Orbits the sun every 75-100,000+

+ years

Comet Structure• Nucleus

–10 km “Dirty Snowball”• Coma

–Cloud of evaporated ices and ions–may be 100,000 km in diameter

• Tail–Always points away from Sun

“A star with hair”

Ion tail pointing directly away from the Sun. Note the slightly bluish color.

Dust tail slightly curved, brighter

Note the two tails

Not to scale!

tail (ions)

coma (a cloud of gas)(~104 km)

nucleus(~10 km)

Sun

tail (dust)

~107 km

Types of Comets• Short-period comets

− originate in Kuiper Belt beyond Neptune

− Return to inner solar system every few years

• Long-period comets

− Originate in the Oort Cloud at the outer limits of the heliosphere

− Return orbits over decades to thousands of years

Oort Cloud

Kuiper Belt

Comet Halley

Hyakutake

Hale-Bopp

Comet West

Bayeaux Tapestry

Comet of 1577

Asteroids• Rocky objects• Contain silicates, iron, and

nickel• Orbit the sun in 1-100 years• Have a diameter of 1-100 km

Asteroids originate from the main Asteroid Belt

found between Mars and Jupiter

Asteroids

Apollo

Trojans

What would happen if a 10 km Asteroid collided with Earth?

The Good Earth, Chapter 3: Near-Earth Objects

What would happen if a 10 km NEO collided with Earth?

1.Fireball racing through atmosphere

2.People at impact site, seconds to live

3.Air blast would flatten everything for hundreds of kilometers in all directions

4.Massive earthquake at collision

5.Ocean impact would produce giant tsunami hundreds of meters high

The Good Earth, Chapter 3: Near-Earth Objects

What would happen if a 10 km NEO collided with Earth?

1.Molten rock from collision would rain down, start massive wildfires

2.Huge cloud of dust blocks sunlight, cools planet for months, kills off most vegetation

3.Gases from impact – sulfur dioxide, water vapor – added to atmosphere

The Good Earth, Chapter 3: Near-Earth Objects

Impact Features

• Craters on Earth

− More than 150 impact craters identified on continents

− Few impact sites identified in oceans Why?

Sites of the 10 largest impact craters on Earth.

The Good Earth, Chapter 3: Near-Earth Objects

Barringer’s Crater

An iron meteorite 100 feet across and 70,000 tons slamed into the Earth at about 43,000mph in the Arizona desert near Flagstaff 40,000 years ago.

Barringer Crater is 4,100 feet wide and 571 feet deep.

Arizona’s Meteor Crater, the most famous example

Meteoroids, Meteors, Meteorites

• Small pieces of space debris (usually parts of comets or asteroids) that are on a collision course with the Earth are called meteoroids

Meteoroids, Meteors, Meteorites

• When meteoroids enter the Earth's atmosphere they are called meteors.

Meteoroids, Meteors, Meteorites

• If the meteors survive and strike the surface of the Earth they are called meteorites.

Meteors - Shooting Stars

• Most meteoroids are tens of meters in diameter or less.

• Enter Earth’s atmosphere and become meteors or “shooting stars”.

• Most meteors are tiny specks of dust. • Larger meteors produce fireballs.

Hannover, 1995 Perseid Shower, 1996

Peekskill, 1992

• What are meteor showers???- result when the Earth encounters cometary orbits

• The annual nature of meteor showers hints to the nature of the orbits of meteoroids.

Sporadic Meteors

• These are the meteors that can be seen on any given night

• They are not associated with any particular meteor shower

• They come from random directions in the sky

Meteor Showers

• Heavy displays of meteors that recur from year to year

• Caused by small fragments of comet debris entering the earth’s atmosphere at extremely high speeds…when the Earth’s orbit & the comet’s orbit intersect at some point

• ‘Shower meteors’ come from the same general point in the sky…

• The radiant of a shower is the point in the sky from which the meteors appear to come

Meteor Showers and Comets• Occur on a regular schedule

Some Meteor Showers

Name Date ofMaximum

Meteors / Hourat Max

Parent

Quadrantids Jan. 4 110 -

Perseids Aug. 12 68 Comet 1862 III

Orionids Oct. 21 30 Comet Halley

Leonids Nov. 17 10 Comet P/Tempel-Tuttle

Geminids Dec. 14 58 3200 Phaethon

Coming to a Theater Near You

Quadrantids............January 2- 4.............30Lyrids.................April 20 - 22.............8Eta Aquarids...........May 2 - 7................10Delta Aquarids.........July 20 to August 14.....15Perseids...............July 29 to August 18.....40Draconids..............Oct 10....................?Orionids...............Oct 17-24................15Taurids................Oct 20 to Nov 25..........8Leonids................Nov 14-19 ................6Andromedids............Nov 15 to Dec 6...........?Geminids...............Dec 8 - 15...............50Ursids.................Dec 19 - 22..............12Ariertids..............May 29 - June 17.........40Zeta Perseids..........June 1-15................30Beta Taurids...........June 23 - July 7.........20

[Source: Dr. Sten Odenwald, Astronomy Café]

Main types of meteorites

• Chondrites–Carbonaceous–Non-carbonaceous

• Achondrites• Iron• Stony-Iron

Chondrites

• Rocky, inhomogeneous, contain round “chondrules”

Microscope image

Carbonaceous Chondrites contain complex organic molecules

• Amino acids, fatty acids, other so-called “building blocks of life”

• Did building blocks of life come to Earth from space?

• Did life itself come to Earth from space?– “Panspermia” theory

Carbonaceous ChondritesMay contain organic compounds that may hold keys to how life developed in the Solar System.

Iron meteorites• Made of iron and nickel• Pits made during atmospheric entry (hot!)

Iron Meteoritesprimarily iron and nickel

Iron meteorites: from core of differentiated asteroids

The making of future meteorites!

Crystalization pattern of the iron is unique

Stony-Iron meteorites - the prettiest

• Crystals of olivene (a rock mineral) embedded in iron• From boundary between core and mantle of large

asteroids?

Achondrites: from Mars and Moon

• From Mars: – Tiny inclusions have same elements and isotope

ratios as Martian atmosphere (measured by spacecraft on Mars)

• From the Moon:– Astronauts brought back rocks from several

regions on the Moon– Some achondrites match these rock types exactly

Meteorite ALH84001

Near Earth Objects: will Earth have another collision soon?