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Artist's depiction of the asteroid belt between Mars and Jupiter. Credit: David Minton and Renu Malhotra
The asteroid field known as the main belt is a large collection of objects that are in orbit between Mars and Jupiter. The largest known asteroid in the belt is Ceres which accounts for over 25% of the belts total mass. Ceres is also the only asteroid in the belt that is classified as a dwarf planet. Vesta, Hygeia, and Pallas are the other of the four largest bodies in the asteroid field. There have been several space missions that have crossed field. The asteroids are far enough apart that traversing it is easily done. The Dawn space mission to the next to visit the main belt and will visit two of the largest bodies.
The Kuiper belt is populated with thousands of icy bodies. The only one that is currently designated as a dwarf planet is the former planet Pluto. That may change in the near future since there are at least two bodies in the belt that are larger than Pluto.
The Trojans asteroid field originally referred to the Trojan asteroids orbiting around Jupiter’s Lagrangian points. Subsequently objects have been found orbiting the Lagrangian points of Neptune and Mars. The adjective Trojan refers to a natural satellite that shares an orbit with a larger planet or moon, but does not collide with it because it orbits around one of the two Lagrangian points of stability.
The scattered disc asteroid field is a subset of the Kuiper belt. Because their orbits take them well beyond 100AU from the Sun they as the coldest objects in the Solar System. Due to its unstable nature, astronomers now consider the scattered disc to be the place of origin for most periodic comets. Many of the objects in the Oort cloud are thought to have originated in the scattered disc.
When we think of an asteroid field, most people conjure thoughts of the main belt. The other three are usually only known by astronomers, both amateur and professional alike. The main reason is that space missions have never made it anywhere but the main belt. It has had all of the press, so all of the glory. There is much more science to be had from the other asteroid fields as well.
Here on Universe Today we have written on the asteroid belts and alien asteroid fields in the past.
There is also some good information on asteroid fields from NASA and Wikipedia.
We have recorded two episodes of Astronomy Cast about asteroids. There’s Episode 55: The Asteroid Belt, and here’s Episode 29: Asteroids Make Bad Neighbors.
References:
NASA: The Asteroid Belt
NASA: Asteroids
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