Where Do Asteroids Come From?

The most common source of asteroids is the main asteroid belt.

Big Bang Explosion and the Asteroid Belt

This belt is situated between Mars and Jupiter. The asteroid belt is not so prolific that it is impenetrable. A number of non-manned space vehicles have traversed the asteroid field without damage.

The materials in the asteroid belt are theorized to have come from the Big Bang explosion. As the planets coalesced, the hot gases mixed and began to cool. The material that was not pulled into one of the planets remained in space and began its own cooling process.

Over thousands of years, the hot gases continued to draw in and form small rocks. The rocks were not large enough or close enough to a planetary gravitational field to be pulled into the planet and contribute to its growing mass. They congregated in the region between the planet of Mars and Jupiter.

Other Asteroid Areas

Other smaller rings of asteroids occur in regions along the orbital path of Jupiter and in the Kuiper Belt.

Composition of Asteroids

Asteroids are made from one of three types of materials:

C-type - Made of carbon containing rocks
S-type - Made of silicon-based rocks
M-types - Large asteroids which contain metal

Asteroids of all three types vary in size dramatically. The largest asteroid on record is Ceres. Ceres is large enough to be considered a minor planet. Ceres amounts for approximately 27% of the total mass of the main belt of asteroids that lie between Mars and Jupiter.

Formation of Asteroids

As various rocks collect in the asteroid belts, collisions continue to occur. When one rock collides with another rock, then they are broken up. This generates a new asteroid and sends all the particles involved in the collision off on new trajectories.

Some of these trajectories send the asteroids towards other bodies in the solar system. They travel on their way through space towards a planet or moon of a planet. As the asteroid enters the atmosphere of the planet or moon, friction takes place and begins to burn off the outer layers of the asteroid. If the size of the asteroid is too small, it will be completely burned up in the atmosphere before it can strike the surface of the planet or moon.

For asteroids that are larger, they will strike the Earth, having reduced their size before striking the ground. By the time they reach the Earth, they may appear as rocks or compounded metal fragments. These fragments can come from any of the regions of asteroid aggregation but the most likely origin is from the asteroid belt between Mars and Jupiter.

Asteroid Sizes

The largest asteroids reside in the asteroid belt and, with the exception of Ceres, are not quite big enough to be classified as dwarf planets. These and all the rest of the asteroids are settled into an orbit around the sun and barring any spatial anomaly will continue on that orbital path. Thus, asteroids present no cause for alarm.

The other three bodies that could present any cause for alarm are Vesta, Hygeia and Pallas. However, despite the fanciful thinking and wonderfully written stories about asteroid collisions with the Earth, none of the asteroids that could be deflected towards Earth are big enough to cause any major catastrophe.

The major events in history that have caused catastrophic effects have been from meteors that fell into the Earth’s gravitational field and were pulled into the atmosphere and friction slowed it enough to pull it down towards the surface of the planet. There are a number of famous sites suspected of being caused by large meteor landing sites. These include: Roswell, NM, Arizona, Siberia, and the area called the Bermuda Triangle in the Caribbean Sea.