What Are Asteroids? And Why Do We Care?

In between paying taxes and dealing with other such minutiae, it’s worth zooming out a bit. With that in mind, here’s a quick take on the what are asteroids question.

 

Some Basics

Asteroids, sometimes called minor planets, are rocky bodies that orbit the sun. The rocky composition lies in contrast to comets, which also orbit the sun but are composed largely of dust and ice.

Of the 1.2 million or so asteroids that have been identified, the majority are found in the so-called asteroid belt, located between the orbits of Mars and Jupiter. That said, they can be found throughout the solar system, and some with eccentric orbits can approach Earth.

Diameters range from 329 miles to the much more modest 33 feet.

Related terms include meteoroids (small pieces of asteroids or comets), which upon entry into Earth’s atmosphere create streaks of light known as meteors (also termed shooting stars). Meteoroids that survive passage through the atmosphere and make it to Earth’s surface are called meteorites.

 

Why Do We Care?

Caring about asteroids is quite reasonable, as collisions between them and our planet can cause serious damage. In fact, it’s postulated that 66 million years ago an asteroid approximately six miles in diameter struck Earth near the Yucatan Peninsula, initiating events that eradicated dinosaurs and paved the way for, um, us (many millions of years later, of course).

Even asteroids that don’t make it all the way to the surface can wreak havoc. In 1908, the atmospheric explosion of an asteroid (perhaps 150 – 300 feet in diameter) over Siberia flattened 80 million trees over 800 square miles of forest.

And the fascination with asteroids goes above and beyond cosmic crashes. The rocky structures date back to the formation of our solar system 4.6 billion years ago, a sort of leftover debris that didn’t make it into any of the planets. Understanding their composition can therefore provide insight into the early days of our tiny nook in the universe.

Along the same lines, when Earth formed, it remains unclear whether all the organic compounds needed to create DNA, RNA, amino acids, and other components of life were present. It’s quite possible that one or more crucial ingredients were established elsewhere—like on an asteroid—and “delivered” to Earth. As an example, sampling from the asteroid Ryugu revealed uracil, critical for the formation of RNA, adding fuel to the theory that a meteoroid turned meteorite could have been the delivery vehicle.

 

But really, what are asteroids you ask? They’re those things you used to shoot in the Atari game. Now get back to those taxes.