What are asteroids? Where do they come from? What are asteroids made or composed of? Are they destructive to life or necessary building blocks for creation? These are all common questions that are asked by people all over the world. The truth is, asteroids are much more than meets the eye. They’re not just big rocks that wander in space without reason. Honestly, normal individuals couldn’t even begin to comprehend or imagine how essential they are for life. As you learn more and more about them you’ll discover that they actually serve a vital purpose in the universe. People who aren’t knowledgeable about them instinctively associate asteroids with fear and just that. Although you can’t blame or fault them on it, the question is should is can we associate them with a more positive word? The answer is yes and no. Let me explain, asteroids are definitely something to be afraid of, but to the same degree, they are also something you should learn to respect.

At the beginning of time, during the creation of the universe, when the cosmos was still at its infancy, there were no planets at all. In fact, one of the first things to form in the vast emptiness of space were asteroids. Actually, if you even attempt to trace the roots of an asteroid you’ll find yourself right at the Big Bang, where it all began. In space, there are literally an unimaginable number of asteroids present, each coming in many different shapes and sizes, seemingly infinite, but somehow finite. It is truly an incredible thing to even conceive of. Seriously, how do you even begin to visualize such a spectacle? Is it even possible to do such a thing? In my opinion, even if it were, it’d be too difficult to accomplish such a task. So what exactly are asteroids anyway? They are small bodies or objects in space that orbit the sun composed mostly/mainly out of rock and metal. Although they aren’t necessarily tiny, in comparison to everything around it, such as stars or planets, they really are miniscule. The size of an object doesn’t necessarily correlate to how important it is though. Fact is, they may be small, but asteroids might be some of the most important physical bodies drifting in the universe. All in all, it’s safe to say we shouldn’t judge a book by its cover.

Anyways, asteroids are also often called “minor planets.” Why exactly are they known as such might you ask? Well, because most planets, specifically the rocky ones, owe their existence to these cosmic boulders. Why are these titans indebted to these puny little pebbles might you say? Well, first of all, for planets to form, it is essential for asteroids to collide and stick to each other. Secondly, they have to be going at the same direction at relatively similar speeds or else they cannot merge or join together. Thirdly, once they eventually collide and fuse, gravity comes into the picture and pulls other nearby asteroids. The bigger and bigger it gets, the stronger its gravitation pull becomes, thereby attracting more and more objects to it. Without the force of gravity, planetary formation would take billions of years, but because of this process (also known as accretion), it doesn’t. Finally, once it becomes massive enough, the gravity molds it into a sphere until ultimately, a planet is born. It is an extremely lengthy process that can take millions of years, but this is how rocky planets like Earth and Mars were formed. Obviously not every single asteroid gets used, so the ones that remain just drift around in space while orbiting the sun.

We have two very large asteroid belts in our very own solar system. In those belts, there are millions, most likely even billions of cosmic rocks just wandering around and around. The main asteroid belt, is located right in between Mars and Jupiter. In it contains four extremely large asteroids called Ceres, Vesta, Pallas, and Hygiea. These giants truly live up to their name as minor planets. Ceres, the largest out of these monstrous asteroids, is apparently as big as 600 miles in diameter. The other three titans are also fairly big with mean diameters of about 250 miles or more. In comparison to the midgets around them, they look like big bad bullies. Overall, the size ranges of an asteroid vary greatly. In space, some can grow to as large as a mountain, while many others can be as small as a speck of dust. A popular theory for why the asteroid belt even exists is supposedly because of Jupiter’s force of gravity. Billions of years ago, giant asteroids were essentially taken off their orbits and then flung in every direction. Because of the gas giant, specifically Jupiter’s gravity, fatal collisions became sort of inevitable for these cosmic boulders. Instead of sticking or joining together to form a new planet, colliding asteroids would shatter and fall apart.

So how scary would it be to get hit by one of these things? What would happen if Earth were struck by an asteroid? Would we survive such a catastrophic event? The answer is it’s mostly dependent on the size of the asteroid and the velocity in which it travels. There are other factors, but those are the two most important ones. The truth is, our planet gets bombarded by millions of small asteroids, or meteoroids, on a daily basis, but because of the Earth’s atmosphere, they tend to burn up and die out before they are able to do any real damage. Our atmosphere basically acts as a shield for our world and protects us from anything outside. Simply put, any minor planet smaller than 25 meters in size isn’t even a small threat to our world’s state of being. On the other hand, according to NASA, any rocky asteroid bigger than 25 meters across would probably cause local damage to its area of impact. They also believe a boulder larger than 1 to 2 kilometers in size could be potentially threatening to our terrestrial planet. The explosion would trigger worldwide damage, destroy cities, and kill millions of people. But because of the Spaceguard Survey and their discovery of nearly 75% of asteroids 1 kilometer and larger, the chances of that happening are pretty slim. It’s as likely as dying from a fireworks accident.

There are also many different kinds of asteroids. A c-type, or carbonaceous, is probably the most common. It’s usually known for being depleted of hydrogen and helium. They are found in the outer regions of our asteroid belt. S-type asteroids, or silicaceous ones, are a little less common, usually made out of metallic iron mixed with iron and magnesium sillicates. You can find most of them in the inner region of the main belt. Finally you have m-type, or metallic asteroids, primarily comprised of metallic iron. These are frequently located in the middle of our main asteroid belt.

NEAs, or near-Earth asteroids, are another group of asteroids that are categorized into three groups. The first are Amors. These are asteroids that intersect Mars’ elliptical orbit and don’t quite reach our planet’s orbit. In other words, they are non-threats. Apollos on the other hand, are asteroids that cross Earth’s orbit within a period of greater than 1 year. Atens is basically the same thing as Apollos, except for the fact that the asteroids take less than a year to intersect our orbit. All in all, near-Earth asteroids are the ones we have to be most cautious about simply because they are seriously not too far away from us. Supposedly there are thousands of these rocks sizable enough to potentially endanger our planet. We’re talking about something 1 kilometer or larger hitting Earth. That’s some major damage potential right there. The largest NEA is called the 1036 Ganymed and it’s about 32 km in diameter. Now if that were to hit our planet, we would be done. Earth would probably get obliterated, simple as that.

In conclusion, I learned asteroids are indeed necessary for life itself. Not only are they important keys to unlocking the mysteries of our universe, but they hold the power to create and destroy at any given moment. As you learn more about them, you realize that many planets are made out of these boulders. These wanderers, some old, some new, are truly building blocks to our existence. Just like humans, they are definitely more than meets the eye. NASA’s curiosity to learn more about them will be beneficial to us in the long run, whether it be to avert future dangers or learn more about our universe. Another thing I learned is that rocks in the main asteroid belt are less likely to reach us then near-Earth asteroids (or NEAs). Obviously, the ones that can actually do harm to us are not the small ones, but the larger boulders that are a mile across or more. Another thing I would compare them to are Lego blocks since they come in different shapes and sizes and are used for building. They certainly have a rather unique and interesting purpose in our space. 





– Beech, M.Steel, D. I. (September 1995). “On the Definition of the Term Meteoroid”.  Quarterly Journal of the Royal Astronomical Society 36 (3): 281–284. Bibcode 1995QJRAS..36..281B.)

– “Asteroids”. NASA – Jet Propulsion Laboratory. Retrieved 13 September2010.


– How the Universe works (Season 2, Episode 7)

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