inward and now lies within Earth's orbit around the Sun. Material other than metals and silicates, due to their higher boiling points, could not persist in solid form. Here planets formed that are mainly rocky, which are Mercury, Venus, Earth, and Mars. Because these refractory materials only comprised a small fraction of the solar nebula, the terrestrial planets could not grow very large.

The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the