Between the red planet, Mars, and the gaseous giant of the Solar System, Jupiter, lies the main Asteroid Belt. The region is home to the majority of asteroids under the influence of the Sun, which many scientists believe to number in the billions. Although most are small, rocky boulders, some are far larger - Ceres, Vesta, Pallas and Hygiea, to name just a few.
The discovery of the first objects in the Asteroid Belt came in the early 1800s. Johann Titius, an 18th Century astronomer, predicted the existence of a planet between the orbits of Mars and Jupiter. Astronomers spent several years searching the sky for this missing planet, until in 1801 Italian astronomer Giuseppe Piazza finally discovered Ceres, the largest object in the Asteroid Belt.
The origins of the Asteroid Belt have long been argued by scientists. Today, the scientific consensus is that the belt was the result of the failure to form another planet. During the early days of the Solar System’s formation, dust and rocks came together to form planets. However, the immense gravitational influence of Jupiter disrupted the formation process of the rocks found between Mars and Jupiter, resulting in a scattering of asteroids between the two planets.
Some asteroids are composed of precious metals such as nickel, iron and titanium. Such metals are sought after on Earth, making asteroids an attractive target for space mining in the future. There have been several proposals from private companies and NASA to develop technologies that would enable asteroid mining to become a reality. One such proposal is the Asteroid Redirect Mission from NASA. Although still in the early stages of planning, the mission would involve retrieving a boulder from a large near-Earth asteroid and redirecting it to a distant retrograde orbit around the Moon. Such an endeavour would allow humans to visit the boulder and analyse its composition to a far higher degree than already possible.
Missions to asteroids are always scientifically fruitful. The Dawn spacecraft not only visited Vesta in 2011, but also entered orbit around Ceres in March of last year and has since sent back valuable data giving scientists on Earth clues as to its history in the Solar System. NASA are expected to learn even more about asteroids when ORIRIS-Rex reaches its target asteroid Bennu in 2018. One of the key scientific objectives of the mission is to return to Earth a sample of the asteroid. Such material could help scientists learn more about the formation and evolution of the early Solar System.