Earth Science Unit 3: Comets, Asteroids and Meteoroids

Why do people think Pluto is a large Kuiper Belt Object (KBO) rather than a true planet?

1. It's orbit is highly eccentric and at times is closer to the Sun than Neptune. 2. It rotates on its side. 3. It rotates in the opposite direction from most of the other planets. 4. Its orbit is tilted from the plane of the ecliptic.

What two places do comets come from?

1. Oort Cloud: have long orbital periods and can enter the solar system from many different directions. 2. Kuiper Belt: a reservoir for the short period comets that we see.

Describe comets far away from the sun.

1. The nucleus is very cold and its material is frozen solid within the nucleus. (like dirty snowballs)

Describe the comets when it nears the sun

1. The surface of the nucleus begins to warm, gases evaporate carrying small solid particles with them, forming the comet's COMA of gas and dust.

What are theories of how asteroids are formed?

1. They are remains of a planet that was destroyed in a massive collision long ago. 2. More likely they are material that never came together into a planet.

What is the size of Pluto?

1/5th the size of the Earth.

What were the next years that Halley's comet was visible?

1910 and 1986

When will Halley's comet come again?

2062

What are meteorites composed of?

92.8% are composed of silicates (silicon and oxygen), and 5.7% are composed of iron and nickel. The rest are a mixture of silicates, iron and nickel called stony-irons and pallasites.

What is a coma?

A luminous cloud of dust and gas that develops around a comet's nucleus as it nears the sun.

What is an asteroid?

A small solar system object in orbit around the sun composed mostly of rock. They are rocky and metallic objects that orbit the Sun but are too small to be considered planets. It is material left over from the formation of the solar system.

What are the temperatures of Pluto?

Average surface temperature of -220 degrees Centigrade

What did Edmond Halley predict?

Based on Isaac Newton's newly formulated laws of motion, he predicted that the comet seen in 1531, 1607, and 1682 would return in 1758. It did return as predicted and was named in his honor.

Where are Main Belt Asteroids located?

Between the orbits of Mars and Jupiter (1.8 to 4.0 AU) in a region know as the asteroid belt.

Where does much of our understanding about asteroids come from?

By examining pieces of space debris that fall to the surface of the Earth.

What is the source of the Orionid meteor shower in October?

Comet Halley is the source.

What is the atmosphere of Pluto?

Has a faint atmosphere made from gases that boil off the surface as it approaches the Sun. When it is far from the Sun, the surface is frozen solid with no atmosphere.

meteorite

If the meteoroid does not burn up completely in the Earth's atmosphere and lands on the surface of the Earth.

Where are Near-Earth Asteroids (NEA's)?

In the area near Earth at around 1 AU (Astronomical Unit...about the distance between the Earth and Sun).

Describe the moons of Pluto.

It has one moon called Charon. It is strange because it is the largest moon next to its primary planet. Some think of Pluto/Charon as a double planet rather than a planet and a moon.

What is the length of the day and year of Pluto?

It is 6 Earth days long and its year 248 Earth years long.

What is the average period of Halley's orbit?

It is 76 years.

Meteoroid

It is a small chunk of interplanetary debris prior to encountering Earth's atmosphere.

What information do we get from the small number of meteors that don't burn up before reaching the ground?

It is our major source of physical information about the rest of the solar system.

Where is Pluto?

It is the farthest planet from the Sun (usually) and is by far the smallest.

When does the Perseid meteor shower occur?

It occurs every year between August 9th and the 13th when the Earth passed through the orbit of comet Swift-Tuttle.

What happens when the Earth passes through the orbit of a comet?

Meteor showers

How many meteors bright enough to see fall to the Earth every day?

Millions of meteors amounting to hundreds of tons of material.

How many asteroids are there?

Over 10,000 asteroids that have been numbered, and more are being found every month.

Which meteorites are the hardest to identify?

Stony meteorites because they look very much like ground rocks.

What is a good example of an asteroid that hit the Earth in times past?

The meteor crater in Arizona

How big would an object be if the total mass of all asteroids were gathered together into a single object?

The object would be less than 1,000 miles across--less than half the diameter of our moon.

What is the origin of the majority of meteorites?

They are believed to be fragments of asteroids.

What is a comet?

They are small, irregularly shaped bodies composed mainly if ice and dust.

Why did scientists think some meteorites came from Mars?

They contained atmospheric gases trapped in melted minerals which match the composition of the Martian atmosphere as measured by the Viking landers in l976.

What do comets develop as they approach the Sun?

They develop enormous tails of luminous material that extends for millions of miles from the head. The tail always faces away from the Sun.

What are the sizes of asteroids?

They range in size of Ceres (1000 km) down to the size of pebbles.

What did scientists learn from the meteorites found on Antarctica?

They were shown to have come from the moon when compared to Apollo mission rocks.

meteor

When the meteoroid passes through the Earth's atmosphere, it is heated by friction and burns, producing a streak of light called a meteor.

What are comets?

small, irregularly shaped bodies composed mainly of ice and dust.