Is the asteroid belt a former planet?

Scientists used to believe that a planet, which orbited the sun, was blasted into pieces and created the asteroid belt, however, theories have now shifted.

The asteroid belt is a torus-shaped region in the galaxy. It is roughly situated between the orbits of the planets Mars and Jupiter. It features multiple solid, irregularly shaped bodies of many sizes, but much smaller than planets, called minor planets or asteroids.

© NASA/McREL

It is also called the main belt, or the main asteroid belt, to distinguish it from other asteroid populations in the galaxy, such as trojan asteroids and near-Earth asteroids. The belt is the smallest circumstellar disc in the Solar System. It is important to note that about half of its mass is contained in the four largest asteroids: Ceres, Hygiea, Pallas and Vesta.

Some astronomers used to believe a planet that orbited the Sun, between the trajectories of Jupiter and Mars, was blasted into pieces. Subsequently, it formed the asteroid belt that exists in our solar system today.

Sean Raymond, an astronomer at the Astrophysical Laboratory of Bordeaux, revealed that there may have been a planet in that area, and it got blown up to smithereens. However, after researchers began to examine the patterns in iron meteorites that fell to the earth, it became clear that it did not come from one parent body.

Because of this, the theory started to shift toward the idea that the belt was full of planetesimals, or pieces of a planet that either had not formed or failed to form. The problem with this theory is that there is not enough material in the asteroid belt to create such a mass. Ceres is the largest asteroid in the belt, as it is approximately the size of Australia, with a mass nearly half that of all the material of the belt.

It is important to note that scientists have not abandoned the idea that the asteroid belt does not represent the leftovers of a former planet. The belt might have come from parts of other plants, or it may be part of a planetesimal, which is like a baby planet that never completely formed before exploding.

© NASA/JPL-Caltech