If you remember, last time we took a look at 10 things you wanted to know about Mars. This time, I thought it would be a great idea to consider 10 facts you might find interesting about somewhere that can be very mysterious – The Asteroid Belt.
1. What is the Asteroid belt?
The Asteroid belt everyone normally thinks about is a region of the Solar System roughly located between the orbits of Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. They range in size from great chunks of rock, hundreds of kilometers across, down to dust particles.
2. Is there just one asteroid belt?
Good question. The one we’re talking about today is now called the Main Asteroid Belt, or Main Belt, to distinguish it from other asteroid fields we have discovered.
See the picture below.
3. How Many Asteroids are there?
Seriously? There are too many to count. But, did you know that half the mass of the main field is contained in its four largest asteroids. Ceres, Vesta, Pallas and Hygeia
I know – give me an Oooooh!
4. Does it contain any Surprises?
Sure. Did you realize that one of those asteroids, Ceres, is in fact, a Dwarf Planet?
Look at this…
This shows us how big Ceres actually is when compared to our Moon.
She has a mean diameter of 950km (590 miles) and as you can see, is large enough to have her own impact craters from other asteroid collisions.
Ceres is made of a rock & ice combination, (rocky core/ice mantle) and is so big – when compared to the other asteroids – that in herself, she contains about 1/3 of the entire mass of the asteroid belt!
5. How did the Asteroid Belt form?
It was once thought that the field came about due to the destruction of an already existing planet that occupied the space between Mars and Jupiter. But we now know that isn’t the case. The different particles are made up of too many different elements to have come from one, single, larger mass.
Additionally, the huge amount of energy that would have been required to destroy a planet, combined with is low combined mass, (only 4% of the Earth’s own Moon), does not support this hypothesis.
Instead it is now believed that as the sun and planets began to form from gravitational accretion, (the process that formed our solar system in the first place), the influence of the newly evolving Jupiter messed things up!
Simply put, a planetesimal forms when the condensing particles slowly come together and stick. Because of the gravitational influence of ‘baby’ Jupiter, those particles that might have formed another planet, were accelerated beyond what was acceptable and crashed into each other instead of sticking. So, all those pieces never had a chance of becoming a planet in the first place.
(Studies of the Main Field have shown that many of the larger members were melted sometime during their early history. A process caused by repeated high energy collisions – so it looks as if this theory is probably correct).
6. So crashes can happen all the time then?
Well, yes and no.
Contrary to popular belief the Main Belt is mostly empty. The asteroids are spread out over such a huge area that you would have to aim very carefully to reach and hit another one. Nonetheless, millions upon millions of asteroids are known to exist. But – to put it into context – only about 200 are known to exceed 100 km in diameter. (And a recent survey with special telescopes managed to catalogue over a million examples that exceeded 1 km in diameter).
That sounds a lot…but when you consider the vast area they are spread over, no its not.
7. Are all asteroids the same?
Actually, there are three main types of asteroid.
C-type – Carbonaceous / S-type – Silicate / M-type – Metallic
Studies have shown the C-type asteroids inhabit the outer regions of the main belt. S-types tend to stick to the inner area. The M-type account for only 10% of all asteroids and appear to be iron-nickel rich. They are scattered everywhere.
In this picture you can see there’s another kind of asteroid, the pallasite. This is called a V-type asteroid and is very rare, thought to come from larger examples that have formed a crust and mantle.
Like the planets, the asteroid belt behaves in a very civilized manner. While some of its members are irregular, most have a circular orbit that stay within the plane of ecliptic. This spread would tend to support the earlier hypothesis that the belt formed at the same time as the rest of the Solar System.
In 1918, Japanese astronomer Kiyotsugu Hirayama noticed that orbits of some asteroids displayed similar parameters. Closer studies revealed these examples to be part of a similar group of family cluster.
Approximately 1/3 of the main belt belongs to one family or another, and so far, we’ve managed to discover up to 30 of them. The most prominent families are:
Flors; Eunoma; Koronis; Eos; Themis and Vespa.
10. Zodiacal Light
Look at this picture
Zodiacal light is a faint, roughly triangular, diffuse white glow seen in the night sky, which appears to extend from the vicinity of the Sun along the ecliptic. It is best seen just after sunset and just before sunrise in spring and autumn.
It is caused by sunlight, scattered through space dust in the zodiacal medium. This, in part, is created by the constant collisions taking place every day within the Main Asteroid belt.
So you see, yet again we have something to be grateful for from one of the main features of our Solar System.
Well, that’s it for today. I hoped you enjoyed this brief look at the Main Asteroid Belt. Next time, we’ll look at 10 interesting things about a rather mysterious character from our Solar System much closer to home…
See you then
An astronomy and law graduate, he is the creator of the international number one bestseller, The IX, and also has the privilege of being a member of the Science Fiction and Fantasy Writers of America and the British Fantasy Society.
When not writing, Andrew devotes some of his spare time to assisting NASA with one of their remote research projects, and writes educational articles for Astronaut.com and Amazing Stories.
He also enjoys Greek dancing and language lessons, being told what to do by his wife, and drinking Earl Grey Tea.
If you would like to find out more, visit his blog or website at:
Latest posts by Andrew Weston (see all)
- Fifty Years and Still Learning. - July 15, 2019
- A Step in the Right Direction: Solar Electric Propulsion (SEP) - January 23, 2019
- So, you’re still interested in Astronomy?Locating the Andromeda Galaxy - August 20, 2018