Comets vs Asteroids
From blazing a trail through the night sky to wiping out the dinosaurs, we've all heard of the chunks of rock or ice traversing our solar system. In our solar system's asteroid belt there are millions of asteroids and at least 1. The rocky objects that are too small to be planets and are categorized either as comets, asteroids or meteoroids. Asteroids are lumps of rock left over from the formation of the solar system 4. They orbit the sun with many of them residing in a part of the solar system called the asteroid belt, which is a torus-shaped field of floating interstellar rocks between Mars and Jupiter. The word asteroid means 'starlike', because astronomers in the 1800s first thought they looked a bit like stars, according to ESA. The total mass of all the asteroids in the solar system combined would actually be less than that of our moon. A picture of the asteroid Eros taken by the robotic NEAR Shoemaker space probe.
Unlike asteroids which are made up solely of rock, comets are made of a mix of ice, rock and gas. But because of the way they're made, as they get closer their ice and dust begin to melt which gives it a beautiful tail. Astronomers have so far counted 3,743 comets, according to NASA's comets page, but there are likely to be billions of comets up there, most of them in something called the Kuiper Belt, which is a region of space just past the planet Neptune. With all the chaos in the solar system caused by the gravitational pull of the sun and massive planets such as Jupiter and Saturn, things have a tendency to collide. Sometimes one asteroid can hit another, with a smaller piece breaking off and becoming something called a meteoroid. But sometimes they don't completely evaporate in the atmosphere and hit the Earth, when this happens they're called meteorites. NASA's Johnson Space Center has a collection of meteorites that acts as a sort of 'meteorite library' for scientists around the world. There are three types of asteroids called C, S, and M types, all with different compositions, according to Arizona State University.
These types of asteroids are very dark in appearance and are among the most ancient objects in the entire solar system, having been out there for billions of years. Then there are the S-types (stony) asteroids which are made up of silicate materials and nickel-iron. Piece of a meteorite identified as coming from the asteroid Vesta. Comets are far more compositionally complex than asteroids, with bits of rock, gas and ice contributing to the way they're made up. One such comet is 67P/Churyumov–Gerasimenko, but a mission to explore it threw up an intriguing mystery. It analyzed more than 35,000 escaping dust grains and found 45% of them to be carbon-based molecules like proteins, carbohydrates — organic matter which could help in the search for alien life. To learn more about the differences between comets, meteors and asteroids, you can watch this video on NASA's website.
Read full article at Space.com