3/24/19

1

Meteoroids! Asteroids! Comets!

Oh, my!

What makes up our Solar System?

• The sun• Planets• Moons• Asteroid belt (between Mars and Jupiter)• Lots of space• All sorts of bits and pieces of rock

3/24/19

2

Meteorite, Meteoroid, Meteor? What’s the difference?

Meteorite vs. Meteoroid

• Meteoroid = while in space a meteorite is called a meteoroid

• Meteorite = a small rock or rocky grain that strikes Earth’s surface

• So the difference is just based on where the rock is when you are describing it

3/24/19

3

Meteor

• Sometimes called a “Shooting Star”

• When a meteorite enters Earth’s atmosphere, friction causes them to burn up, producing a streak of light

Where do they come from?How big are they?

• Pieces of rock that broke off other objects• Sizes range from as small as a pebble or

as big as a huge boulder

3/24/19

4

Are they dangerous?

• Most meteoroids disintegrate before reaching the earth by burning up in Earth’s atmosphere

• Some leave a trail that lasts several minutes

• Meteoroids that reach the earth are called meteorites. Large ones can cause damage

Flagstaff, Arizona

• 49,000 years ago• Meteorite about 150

feet in diameter • Weighed 650 pounds• Energy = 2.5 million

tons of dynamite• 4000 feet wide, 650

feet deep• Still visible today

Barringer Meteorite Crater

3/24/19

5

What’s a “Meteor Shower”?

• Usual rate = six meteors per hour

• During a Meteor Shower = rate may be as

high as 60 meteors per hour

• Occur when Earth passes through the tail

or debris of a comet

• Presides (mid-August)

• Leonids (mid-November)

Comets

• Bodies in space made up of ice, dust, small gritty particles

• Sometimes called “dirty snowballs”• When close to the sun, ice vaporizes,

producing a spectacular streak of gas, referred to as a “tail”

• Many in a regular orbit around the sun

3/24/19

6

Comets

Where do comets come from?

• Many ordinate in a region called the Oort cloud which is located beyond the orbit of the dwarf planet Pluto

• Others originate in the Kuiper Belt beyond the orbit of Neptune

• This region is filled with billions of comets

3/24/19

7

Famous Comets

• Comet Hale-Bopp

• Halley’s Comet

• Comet Kohoutek

A Comet’s Tail

3/24/19

8

Asteroids

• An irregularly shaped rocky object in space (like a space potato)

• May be the shattered remains of objects left over from the time when the planets were formed

How big are asteroids?

• Larger than meteoroids • (In fact, the main difference between

meteoroids and asteroids is their size.)

• Size ranges from 10 feet across to bigger than a mountain

3/24/19

9

Asteroids

• Approx. 150,000 asteroids in the Solar System

• Most are in a band that orbit the sun between Mars and Jupiter (Asteroid Belt)

• Why are there all of those asteroids between Mars and Jupiter and not another planet?

Near-Earth Asteroids (NEAs)

• At least 1000 asteroids orbit outside of the Asteroid Belt – these could be a danger to Earth

• Asteroids that cross Earth’s orbit are called Near-Earth Asteroids or NEAs

• NEA / Earth collision not likely• But if it did, the affect of the impact would

depend on the size of the asteroid

3/24/19

10

Large Asteroid hits Earth 65 Million Years Ago

• Catastrophic Collision• Asteroid 6 to 12 miles

in diameter• Near the Yucatan

Peninsula in the Gulf of Mexico

Large Asteroid hits Earth 65 Million Years Ago

• Collision produced an explosion = 100 trillion tons of dynamite

• Gouged out a crater about 60 miles in diameter

• How would an event like this affect Earth?

3/24/19

11

What do Scientists Think Happened?

• Forests were wiped clean for a distance of 300 to 600 miles in all directions

• 300 foot wave struck the coast of Texas• Powerful Earthquakes• Landslides destroyed long stretches of

coastline

What do Scientists Think Happened

• Explosion threw huge amounts of debris into the air, covering large parts of North America

• Poisonous gases and dust soared high into the atmosphere, spread over most of the Earth, and then fell back onto the Earth’s surface

3/24/19

12

What do Scientists Think Happened

• Sunlight was blocked from reaching the Earth’s surface for many months

• Temperatures plummeted to the freezing point in normally warm areas

• Not enough sunlight for photosynthesis• Plants died . . . Animals died• Many animals became extinct (including

many types of dinosaurs)

The Rise and Fall of Life on Earth

• See the dip around 65 Million years ago?• This represents the extinction of about 75% of all

the species alive at that time.

3/24/19

13

Is the Earth in danger of a large asteroid impact?

• Not that we know of! • None of the asteroids or comets

discovered so far is on a collision course with Earth.

• However, we can't speak for those that are not yet discovered. In principle, one of those could hit any time, but statistically the chances are very small.

Torino Scale

• A system used to rate the hazard level of an object moving toward Earth

3/24/19

14

Review• Q: What is the difference between a

meteoroid, meteororite, and a meteor?

• Meteoroid = while in space a meteorite is called a meteoroid

• Meteorite = a small rock or rocky grain that strikes Earth’s surface

• Meteor = “Shooting Star”

Review

• Q: What is the difference between an asteroid and a meteoroid?

• The main difference is the size of the object.

• Q: Which is larger, asteroid or meteoroid?• Asteroids are larger than meteoroids.

3/24/19

15

Review

• Q: Why is it important to study smaller bodies in our Solar System such as comets or asteroids?

• They help us learn about the history of our Solar System.

Review

• Q: Why do planets and moons with atmospheres have less impact craters than those without atmospheres?

• The atmosphere slows and burns smaller objects like meteorites, thus many do not reach the surface to create an impact.

3/24/19

16

Review

• Bright streaks of light that result when rocky bodies burn up in the atmosphere are called ___________.

• Frozen bodies made of ice, rock, and dust, sometimes called “dirty snowballs” are called _____________.

• Small, rocky bodies that revolve around the sun are called ______________.

Review

• Bright streaks of light that result when rocky bodies burn up in the atmosphere are called meteors.

• Frozen bodies made of ice, rock, and dust, sometimes called “dirty snowballs” are called comets.

• Small, rocky bodies that revolve around the sun are called asteroids.

3/24/19

17

Review

• Q: Discus what could happen if the Earth experienced another large asteroid impact. How would it affect life on Earth?

• Forests flattened for many miles• If asteroid landed in water, it would cause

giant waves and landslides• Powerful Earthquakes

The devastation continues…

• Poisonous gases and dust fills the atmosphere, blocks out the sun

• Temperatures drop drastically• No photosynthesis = plants die = animals

die• Some animals become extinct

3/24/19

18

Review

• Q: Where is the Asteroid Belt?• Asteroid Belt is between Mars and Jupiter

• Q: What is the Torino Scale?• A system used to rate the hazard level of

an object moving toward Earth