The planet closest to the asteroid belt is Mars. The asteroid belt is located between the orbits of Mars and Jupiter, making Mars the nearest planet to this region filled with numerous rocky and metallic objects.
To understand this better, let’s look at the layout of our solar system. The planets are arranged in a specific order from the Sun: Mercury, Venus, Earth, Mars, the asteroid belt, Jupiter, Saturn, Uranus, and Neptune. Since Mars comes right before the asteroid belt, it is indeed the closest planet to this area.
Moreover, the asteroid belt serves as a fascinating boundary between the inner rocky planets (Mercury, Venus, Earth, and Mars) and the outer gas giants (Jupiter and beyond). The unique composition of asteroids provides valuable insights into the early solar system, as these objects are remnants from its formation.