Asteroids, Comets, and Their Impacts

Meteoroids

Small rocks (less than a few meters across) travelling through space.

Meteors

Small rocks from space that light up in the night sky as they burn up in the Earth's atmosphere.

Meteorites

Small pieces of space rock that survive passage through the atmosphere to be picked up on the surface.

Asteroids

Large space rocks that range in size from meters to 100s of kilometers.

Comets

Dirty iceballs (a mixture of ice and rock) as old as the solar system itself.

Regolith

A layer of loose dust and small particles left over from many impacts.

Asteroid Belt

Most of this ancient space rubble can be found in the main asteroid belt located between Mars and Jupiter.

Crowded Asteroid Belt

Not crowded; the average distance between 1 km-diameter main belt asteroids is more than 500,000 km.

Mass of Asteroid Belt

The total mass of the asteroid belt adds up to just 4% of the mass of the Moon.

Comets as Dirty Ice Balls

Due to being a mixture of ice and rock that are just as old as the solar system itself.

Comet Tails

The gas tail is composed of molecules ionized by ultraviolet light from the Sun, causing it to emit blue light.

Direction of Gas Tail

The gas tail is pushed directly away from the Sun by the solar wind (charged particles streaming from the sun).

Meteor Showers

Meteor showers are created when the Earth passes through the remnants of broken up comets.

Haley's Comet

Because you can only see it once in a lifetime (76 years).

Oort Cloud Shape

We know that the Oort cloud is a sphere because long-period comets come at us from all directions.

Asteroid Size and Crater Size

The higher the speed of the asteroid, the bigger the impact and crater.

Impact Crater Shape

The explosion upon impact causes a large enough explosion to affect every direction.

Lunar Impact Craters

They become filled with lava called mare which smoothens out the surface.

Impact Craters on Moon vs Earth

The Moon has no erosional processes to erase old impact craters.

Evidence of Dinosaur Extinction

The thin layer of clay that separates Cretaceous from Paleogene sediments all over the world contains a lot of iridium, shocked quartz, and soot, indicative of a giant impact and global fire.

Strategies for Changing Orbits

Kinetic Impact, Spacecraft propulsion, Solar sail, Nuclear weapons, Deflection.