The Asteroid Belt - it’s one of the most fascinating areas of our Solar System, and it’s also probably the one most often portrayed inaccurately in TV shows and movies.
It is usually depicted as a perilous obstacle course of flying rocks. Even in my favorite series, the Cosmos reboot, Neil deGrasse Tyson is shown darting around it in his Spaceship of the Imagination like he’s steering the Millennium Falcon through a sea of debris.
But it turns out: the Asteroid Belt is pretty empty.
Located between the orbits of Mars and Jupiter, the Belt covers an enormous region about 2 to 3 times the size of Earth’s distance from the Sun. (That’s around 50 trillion cubic kilometers). And while most of that is empty space, it does contain trillions of space rocks, ranging in sizes from tiny bits of dust to the size of Texas. Together, they have perplexed astronomers for centuries.
So where did the Asteroid Belt come from?
Astronomers used to think that it held the remnants of a planet that was destroyed by a comet, or a collision with some other planet, in the earliest days of the Solar System’s formation.
But after some lengthy research, astronomers have decided that there isn't enough mass in the Asteroid Belt to account for even a small terrestrial planet.
So far, we’ve found only four objects in it that are more than 400 kilometers in diameter: the asteroids Vesta, Pallas and Hygiea, plus the dwarf planet Ceres. Together, those four objects contain more than half of the total mass of the Asteroid Belt, with Ceres accounting for most of that.
There are also too many chemical differences among the asteroids for them to have originated from a single object. Most of them are composed of rocky minerals, for example, while a few contain mostly metals like iron and nickel.
So, more than likely, the asteroids are just remnants of the Solar System’s formation 4.5 billion years ago.
As our Solar System’s giant disc of gas and dust slowly grew into larger and larger particles - eventually forming planets - some bits of the material weren’t able to collect into anything. In the Asteroid Belt’s case, the enormous gravitation of Jupiter likely prevented those particles from coalescing into even a small planet. And they aren't the only leftovers we’ve found from those early days.
The Asteroid Belt is sometimes referred to as the “Main Belt,” to distinguish it from the Kuiper Belt out past Neptune. And in the effort to learn more about the souvenirs of the Solar System’s birth still floating around in space, NASA has sent the Dawn spacecraft to investigate.
In 2011, Dawn orbited Vesta, where it mapped the giant asteroid’s entire surface, and discovered that it’s more geologically complex than we thought originally, with a crust, mantle, and iron core, more like a protoplanet than just a chunk of rock.
And in 2015, Dawn met Ceres, the largest object between Mars and Jupiter, which has already been found to have water ice on its surface and even a thin atmosphere. This info is important because Dawn joins more than a dozen other spacecraft that have navigated safely through the Asteroid Belt - Pioneer 10 became the first to make its way through in 1972, with no laser cannons needed!
Therefore, proving the case that it wasn’t some celestial mine field. Sorry, Neil.
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Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Hofmeister, Caitlin. “The Asteroid Belt: Not What You Think!” SciShow Space, YouTube. 21 May 2014. Web video.
DeGrasse-Tyson, Neil, and MacFarlane, Seth. “The Cosmos: A Spacetime Odyssey.” FOX Home Entertainment, 9 Mar. 2014. Television.
Citation: Rovira, Lia N. "The Asteroid Belt: Not What You Think!" SkyFeed. 31 Jan, 2018. Web article.