Living In The Asteroid Belt – part 2 – Geography and Geology

Living In The Asteroid Belt – part 1 – Introduction was the previous article in this series.

The inner planets of our Solar System are Mercury, Venus, Earth, and Mars. By convention, the orbital distance of the Earth from the Sun has been established as 1 Astronomical Unit (AU). The orbit of Mars is near 1.5 AUs. The main asteroid belt is found between 1.8 AUs and 4.5 AUs. Jupiter is next at 5.2 AUs and Saturn and the rest of the outer planets beyond that.

Asteroid Belt

Asteroid Belt

Over time, asteroids come under the gravitational influence of nearby planets and other asteroids and collide with each other and fragment. This results in groups or clusters being formed by similarities in orbital trajectories. These groups are called “families”. The families may also be the result of how the asteroids were originally formed. Both the number of families that exist and the number of members found in each family depends upon how the groups are identified and this can vary. But there seems to be some agreement for about forty major families and there may be more than a hundred such groups. Depending on the categorization process being used, each family may have only a few members or more than ten thousand in a single group.

In addition to the groups of families, the gravity of Jupiter in particular has swept out some empty regions or gaps in the asteroid belt based on orbital harmonics. Since this was first documented by an astronomer named Kirkwood, they have become known as the Kirkwood gaps.

Here is a graphic that shows both the Kirkwood gaps and some of the families:

Asteroid Groups

Asteroid Groups

The popular concept of how much space is between individual rocks in the asteroid belt has been wildly distorted by movies and other fiction. Instead of thick fields of rocks that need skillful maneuvers to navigate, the truth is more like a small handful of grains of sand scattered over a plane of glass the size of many football fields.

How Dense is the Asteroid Belt?

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Asteroids are put into three categorizations based on their composition:

  • C-type (Carbon) are the most common and are composed of clay and rock containing silicates. They are found farther from the Sun and probably contain more water.
  • S-type (Silicate/Stony) are composed of nickel-iron and other stony materials. They are the second most common type.
  • M-type (Metallic) are composed of nickel-iron and other metals but are less common.

Valuable metals found in asteroids include: gold, silver, platinum, iridium, palladium, and more. Other metals such as: titanium, aluminum, nickel, iron and more will be more likely to be used locally for construction and manufacturing.

The highest value of all substances will be the frozen volatile gases which will include hydrogen, oxygen, and more.

The next article in this series will be about:

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