Small Bodies in the Solar System

1. Pgs. 83 - 87 Small Bodies in the Solar System

2. Comets • A comet is a small body of ice, rock and cosmic dust loosely packed together. • They are sometimes referred to as “dirty snowballs” because of their composition. • They are most likely leftovers from the process of planet formation. • Scientists try to study comets to piece together the physical and chemical history of the solar system.

3. Comet Tails • When a comet passes close enough to the sun, solar radiation heats the water ice so that the comet gives off gas and dust. • Sometimes a comet shows two tails: an ion tail and a dust tail. • An ion tail consists of electrically charged particles called ions. • The dust tail are bits of rock particles. • The nucleus of the comet is the solid center of the comet. • Nuclei can range .5 – 100km in diameter.

5. Comet Orbits • Comet orbits are highly elliptical; very elongated circles. • A comet’s ion tail always points directly away from the sun. • The sun gives of solar wind that blows the comet’s tail away from the sun. • The dust tail follows the comet’s orbit and does not always face away from the sun.

7. Comet Origins • Scientists think that comets come from a spherical region called the Oort cloud, that surrounds the solar system. • When the gravity of a passing planet or star disturbs part of the cloud, comets can be pulled toward the sun. • Another possible origin is just outside Neptune’s orbit called the Kuiper belt.

9. Asteroids • Asteroids are small rocky bodies in orbit around the sun. • They range in size from a few meters to 900km in diameter. • They have irregular shapes. • Most orbit the sun between Mars and Jupiter in an area called the Asteroid belt.

10. Types of Asteroids • Asteroids are classified based on where they are located within the asteroid belt. • Those in the outermost region of the belt are dark reddish brown to black in color, indicating organic matter. • Closer to the sun, they have dark gray surfaces, indicating carbon. • The innermost asteroids are light gray in color, indicating a stony/metallic composition

12. Meteoroids • A meteoroid is a small rocky body orbiting the sun. • They are similar to asteroids but much smaller. • A meteorite is a meteoroid that enters Earth’s atmosphere and hits the ground. • As it falls to Earth, the atmosphere burns up much of a meteoroid’s matter. • If a meteoroid falls to Earth, but burns up before hitting the ground it is a meteor (shooting star).

13. Meteor Showers • Meteors are small pebble sized rocks and can be seen on clear nights, away from city light. • At certain times of the year, large amount of dust particles enter the atmosphere forming meteor showers.

15. Types of Meteorites • The three types of meteorites are stony, metallic and stony-iron. • Scientists study the meteorites that fall to Earth in order to study the solar system and its building blocks.

17. The Role of Impacts in the Solar System and Earth • Celestial bodies without atmospheres have more impact craters than those that do. • Earth has an atmosphere and tectonic motion allowing the meteoroids to burn up and reshape the surface of the Earth. • Scientists estimate that impacts powerful enough to cause a natural disaster might occur once every few thousand years. • An impact that would cause a global catastrophe occurs once every 30 – 50 million years