When we get to about 2 to 3 Astronomical Units, we come not to a planet, but to the Asteroid Belt. This is a region containing millions of rocky objects orbiting the Sun. The largest object is Ceres, which is large enough to be classified as a dwarf planet.

A planet might have formed in this region, but the enormous gravitational influence of nearby Jupiter disrupted the process. Despite the millions of asteroids, there isn't actually very much material here. If you put the entire Asteroid Belt together, it would have only about 4% of the mass of our Moon.

One object in the Asteroid Belt, Psyche, may be the exposed core of a small planet that was stripped apart by collisions. A spacecraft, also named Psyche, is currently on its way to study it.

If that idea is correct, Psyche could give us a rare opportunity to study material similar to the cores of rocky planets like Earth—something we can never reach directly on our own planet.

To continue, move to Jupiter, then press Jupiter on your phone